Peter M. Kappeler

Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.

Although the invention and widespread use of artificial light is clearly one of the most important human technological advances, the transformation of nightscapes is increasingly recognized as having adverse effects.Night lighting may have serious physiological consequences for humans, ecological and evolutionary implications for animal and plant populations, and may reshape entire ecosystems.However, knowledge on the adverse effects of light pollution is vague.In response to climate change and energy shortages, many countries, regions, and communities are developing new lighting programs and concepts with a strong focus on energy efficiency and greenhouse gas emissions.Given the dramatic increase in artificial light at night (0 -20% per year, depending on geographic region), we see an urgent need for light pollution policies that go beyond energy efficiency to include human well-being, the structure and functioning of ecosystems, and inter-related socioeconomic consequences.Such a policy shift will require a sound transdisciplinary understanding of the significance of the night, and its loss, for humans and the natural systems upon which we depend.Knowledge is also urgently needed on suitable lighting technologies and concepts which are ecologically, socially, and economically sustainable.Unless managing darkness becomes an integral part of future conservation and lighting policies, modern society may run into a global self-experiment with unpredictable outcomes.

Year-round association between adult males and females is common in primates, even though internal gestation and lactation predispose males to mate-desertion in the majority of mammals. Because there is little a priori support for alternative explanations, we hypothesized that permanent male-female association in primates serves to reduce the risk of infanticide by strange males whenever females and infants are closely associated. For a phylogenetic test of this hypothesis, we reconstructed the evolution of male-female and female-infant association among primates. The results of Maddison's concentrated changes test confirmed the prediction that mother-infant association, as opposed to infant parking, and female-male association did not evolve independently. Changes in litter size and activity, in contrast, were not significantly associated with evolutionary changes in male-female association. Thus, we demonstrate a fundamental link between primate life history and social behaviour, explain the most basic type of variation in primate social organization, and propose an additional determinant of social organization that may also operate in other mammals.

Social complexity has been one of the recent emerging topics in the study of animal and human societies, but the concept remains both poorly defined and understood. In this paper, I critically review definitions and studies of social complexity in invertebrate and vertebrate societies, arguing that the concept is being used inconsistently in studies of vertebrate sociality. Group size and cohesion define one cornerstone of social complexity, but the nature and patterning of social interactions contribute more to interspecific variation in social complexity in species with individual recognition and repeated interactions. Humans provide the only example where many other unique criteria are used, and they are the only species for which intraspecific variation in social complexity has been studied in detail. While there is agreement that complex patterns emerge at the group level as a result of simple interactions and as a result of cognitive abilities, there is consensus neither on their relative importance nor on the role of specific cognitive abilities in different lineages. Moreover, aspects of reproduction and parental care have also been invoked to characterize levels of social complexity, so that no single comprehensive measure is readily available. Because even fundamental components of social complexity are difficult to compare across studies and species because of inconsistent definitions and operationalization of key social traits, I define and characterize social organization, social structure, mating system, and care system as distinct components of a social system. Based on this framework, I outline how different aspects of the evolution of social complexity are being studied and suggest questions for future research. Animal and human societies differ in social complexity, i.e., the number and association patterns of group members as well as the nature and patterning of their social relationships, but the dimensions of social complexity, the processes that generate it, the selective forces that engender different levels of social complexity, and the evolutionary consequences of this variation remain to be comprehensively understood. Here, I offer a conceptual framework for the systematic and comparative studies of social complexity by defining its main components as well as their proximate and ultimate relationships.

In 1987, the University of Chicago Press published Societies, the standard reference in the field of primate behavior for an entire generation of students and scientists. But in the twenty-five years since its publication, new theories and research techniques for studying the Primate order have been developed, debated, and tested, forcing scientists to revise their understanding of our closest living relatives. Intended as a sequel to Societies, Evolution of Primate Societies compiles thirty-one chapters that review the current state of knowledge regarding the behavior of nonhuman primates. Chapters are written by leading authorities in the field and organized around four major adaptive problems primates face as they strive to grow, maintain themselves, and reproduce in the wild. The inclusion of chapters on the behavior of humans at the end of each major section represents one particularly novel aspect of the book, and it will remind readers what we can learn about ourselves through research on nonhuman primates. The final section highlights some of the innovative and cutting-edge research designed to reveal the similarities and differences between nonhuman and human primate cognition. Evolution of Primate Societies will be every bit the landmark publication its predecessor has been.

This paper introduces a theme issue presenting the latest developments in research on the impacts of sociality on health and fitness. The articles that follow cover research on societies ranging from insects to humans. Variation in measures of fitness (i.e. survival and reproduction) has been linked to various aspects of sociality in humans and animals alike, and variability in individual health and condition has been recognized as a key mediator of these relationships. Viewed from a broad evolutionary perspective, the evolutionary transitions from a solitary lifestyle to group living have resulted in several new health-related costs and benefits of sociality. Social transmission of parasites within groups represents a major cost of group living, but some behavioural mechanisms, such as grooming, have evolved repeatedly to reduce this cost. Group living also has created novel costs in terms of altered susceptibility to infectious and non-infectious disease as a result of the unavoidable physiological consequences of social competition and integration, which are partly alleviated by social buffering in some vertebrates. Here, we define the relevant aspects of sociality, summarize their health-related costs and benefits, and discuss possible fitness measures in different study systems. Given the pervasive effects of social factors on health and fitness, we propose a synthesis of existing conceptual approaches in disease ecology, ecological immunology and behavioural neurosciences by adding sociality as a key factor, with the goal to generate a broader framework for organismal integration of health-related research.

Abstract Home range estimation is routine practice in ecological research. While advances in animal tracking technology have increased our capacity to collect data to support home range analysis, these same advances have also resulted in increasingly autocorrelated data. Consequently, the question of which home range estimator to use on modern, highly autocorrelated tracking data remains open. This question is particularly relevant given that most estimators assume independently sampled data. Here, we provide a comprehensive evaluation of the effects of autocorrelation on home range estimation. We base our study on an extensive data set of GPS locations from 369 individuals representing 27 species distributed across five continents. We first assemble a broad array of home range estimators, including Kernel Density Estimation ( KDE ) with four bandwidth optimizers (Gaussian reference function, autocorrelated‐Gaussian reference function [ AKDE ], Silverman's rule of thumb, and least squares cross‐validation), Minimum Convex Polygon, and Local Convex Hull methods. Notably, all of these estimators except AKDE assume independent and identically distributed ( IID ) data. We then employ half‐sample cross‐validation to objectively quantify estimator performance, and the recently introduced effective sample size for home range area estimation () to quantify the information content of each data set. We found that AKDE 95% area estimates were larger than conventional IID ‐based estimates by a mean factor of 2. The median number of cross‐validated locations included in the hold‐out sets by AKDE 95% (or 50%) estimates was 95.3% (or 50.1%), confirming the larger AKDE ranges were appropriately selective at the specified quantile. Conversely, conventional estimates exhibited negative bias that increased with decreasing . To contextualize our empirical results, we performed a detailed simulation study to tease apart how sampling frequency, sampling duration, and the focal animal's movement conspire to affect range estimates. Paralleling our empirical results, the simulation study demonstrated that AKDE was generally more accurate than conventional methods, particularly for small . While 72% of the 369 empirical data sets had >1,000 total observations, only 4% had an >1,000, where 30% had an <30. In this frequently encountered scenario of small , AKDE was the only estimator capable of producing an accurate home range estimate on autocorrelated data.

The evolutionary transition from a solitary to a social lifestyle entails an elevated parasite cost because the social proximity associated with group living favors parasite transmission. Despite this cost, sociality is widespread in a large range of taxonomic groups. In this context, hosts would be expected to have evolved behavioral mechanisms to reduce the risk of parasite infection. Few empirical studies have focused on the influence of pathogen-mediated selection on the evolution of antiparasitic behavior in wild vertebrates. We report an adaptive functional relationship between parasitism and social behavior in mandrills, associated with evidence that they are able to gauge parasite status of their group members. Using long-term observations, controlled experiments, and chemical analyses, we show that (i) wild mandrills avoid grooming conspecifics infected with orofecally transmitted parasites; (ii) mandrills receive significantly more grooming after treatment that targets these parasites; (iii) parasitism influences the host's fecal odors; and (iv) mandrills selectively avoid fecal material from parasitized conspecifics. These behavioral adaptations reveal that selecting safe social partners may help primates to cope with parasite-mediated costs of sociality and that "behavioral immunity" plays a crucial role in the coevolutionary dynamics between hosts and their parasites.

Information on genetic structure can be used to complement direct inferences on social systems and behaviour. We studied the genetic structure of the solitary grey mouse lemur (Microcebus murinus), a small, nocturnal primate endemic to western Madagascar, with the aim of getting further insight on its breeding structure. Tissue samples from 167 grey mouse lemurs in an area covering 12.3 km2 in Kirindy Forest were obtained from trapping. The capture data indicated a noncontinuous distribution of individuals in the study area. Using 10 microsatellite markers, significant genetic differentiation in the study area was demonstrated and dispersal was found to be significantly male biased. Furthermore, we observed an overall excess of homozygotes in the total population (F(IT) = 0.131), which we interpret as caused by fine-scale structure with breeding occurring in small units. Evidence for a clumped distribution of identical homozygotes was found, supporting the notion that dispersal distance for breeding was shorter than that for foraging, i.e. the breeding neighbourhood size is smaller than the foraging neighbourhood size. In conclusion, we found a more complex population structure than what has been previously reported in studies performed on smaller spatial scales. The noncontinuous distribution of individuals and the effects of social variables on the genetic structure have implications for the interpretation of social organization and the planning of conservation activities that may apply to other solitary and endangered mammals as well.

Explanations of the evolution of canine tooth size sexual dimorphism in primates implicitly assume that male canine size is the primary target of natural or sexual selection, even though there is substantial unexplained variation in female canine size. Here we demonstrate that the canines of both males and females are relatively larger in species where agonistic interactions are more likely to escalate. Hence, the canine teeth of both sexes are influenced by selection for the development of weaponry, though the nature of the selection (natural or sexual) favoring development of the canines as weapons depends on the objects of competition (mates vs. food, for example). However, we also suggest that where the outcome of fights is typically determined between coalitions of individuals, selection for weaponry is reduced, even though agonistic competition can be very intense. Coalitionary aggression between males occurs in only a handful of anthropoid primates, but it is common among female anthropoids, and helps explain, in part, the extreme sexual dimorphism in the canine teeth of a number of catarrhine species. This is the first demonstration that cooperation among animals may affect their morphology. The lack of sexual dimorphism in canine size among prosimian primates is also consistent with the model. This analysis demonstrates that a better understanding of the interspecific variation in sexual dimorphism among primates is gained by considering behavioral variation in both sexes.

Abstract Two semifree-ranging groups of ringtailed lemurs (Lemur catta) and two co-ranging groups of redfronted lemurs (Eulemur fulvus rufus) were studied across a two-year period to characterise and contrast the adult agonistic behaviour these primates exhibit within groups. Temporal analyses of behavioural data distinguished agonistic from non-agonistic behaviour and aggressive from submissive behaviour. The ringtailed lemurs employed a diverse repertoire of behavioural elements to communicate agonistic intent. More than 50% of these elements were signals and nearly 50% of signals were submissive. The agonistic repertoire of the redfronted lemurs, by contrast, was relatively unelaborated: less than 40% of agonistic behaviour in this species comprised signals and less than 20% of signals were submissive. These structural differences underlay marked species differences in agonistic interaction and relationship. All pairs of ringtailed lemurs maintained dominance relations resembling those seen in many anthropoid primates: subordinates consistently signalled submissively to dominant partners, often in the absence of aggression. Dominance relations among members of each sex were seasonally unstable and not always transitive (hierarchical) during periods of stability, however. Redfronted lemurs, by contrast, did not maintain dominance relations, failing to respond agonistically to most aggression received (52% of interactions) and responding with aggression on many other occasions (12%). Even applying relaxed criteria, few adult redfronted dyads (14%) showed consistent asymmetries in agonistic relations and several never exhibited any asymmetry. Lacking dominance, E. f rufus relied heavily on alternate behavioural mechanisms to moderate social conflict as frequent and intense as that seen in study groups of ringtailed lemurs. These included a great inclination not to respond agonistically to aggression, a distinctive behavioural proposal to limit or terminate dyadic conflict (Look away), post-conflict reconciliation, and relatively frequent third-party aggression. The existence of such divergent systems of agonistic behaviour in partially sympatric, closely related and generally similar prosimian primates offers important opportunities for comparative study of the ecology, development, and evolution of mammalian social systems. Future research may reveal ecophysiological factors that promote the use of dominance behaviour among like-sexed ringtailed lemurs and show how the relative absence of dominance relates to other major elements of redfronted lemur biology, including 'special relationships' of variable duration between adult males and females.

Many primatologists believe that there is no sexual dimorphism in body size in prosimian primates. Because this belief is based upon data that came from only a few species and were largely flawed in some aspect of sample quality, I re-examined the extent of sexual dimorphism in body weight, using weights of 791 adult prosimians from 34 taxa recorded over the last 17 years at the Duke University Primate Center. There was no significant sex difference in body weight in 17 species, but males were significantly larger in Nycticebus pygmaeus, Tarsius syrichta, Galago moholi, Galagoides demidovii, Otolemur crassicaudatus and Otolemur garnettii . Moreover, females were significantly larger in Microcebus murinus . Thus, the general lack of sexual dimorphism could be confirmed, notably for lemurs, but prosimians as a group show more variability in sexual size dimorphism than was previously thought. After including previously published data obtained in the wild from 8 additional species, I found significant heterogeneity in the degree of sexual dimorphism at the family level, but only the Indridae and Galagidae were significantly different from each other. Among the prosimian infraorders, the Lorisiformes were significantly more dimorphic than the Lemuriformes. Differences in dimorphism between higher taxonomic groups are discussed in the context of prosimian evolution, concluding that phylogenetic inertia cannot provide a causal explanation for the evolution of sexual dimorphism. The relative monomorphism of most prosimians may be related to allometric constraints and, especially in the Lemuriformes, to selective forces affecting male and female behavioral strategies.

Lemurs and the other strepsirrhine primates are of great interest to the primate genomics community due to their phylogenetic placement as the sister lineage to all other primates. Previous attempts to resolve the phylogeny of lemurs employed limited mitochondrial or small nuclear data sets, with many relationships poorly supported or entirely unresolved. We used genomic resources to develop 11 novel markers from nine chromosomes, representing approximately 9 kb of nuclear sequence data. In combination with previously published nuclear and mitochondrial loci, this yields a data set of more than 16 kb and adds approximately 275 kb of DNA sequence to current databases. Our phylogenetic analyses confirm hypotheses of lemuriform monophyly and provide robust resolution of the phylogenetic relationships among the five lemuriform families. We verify that the genus Daubentonia is the sister lineage to all other lemurs. The Cheirogaleidae and Lepilemuridae are sister taxa and together form the sister lineage to the Indriidae; this clade is the sister lineage to the Lemuridae. Divergence time estimates indicate that lemurs are an ancient group, with their initial diversification occurring around the Cretaceous-Tertiary boundary. Given the power of this data set to resolve branches in a notoriously problematic area of primate phylogeny, we anticipate that our phylogenomic toolkit will be of value to other studies of primate phylogeny and diversification. Moreover, the methods applied will be broadly applicable to other taxonomic groups where phylogenetic relationships have been notoriously difficult to resolve.

Abstract The four major hypotheses advanced to explain the evolution of sexually dimorphic characters invoke sexual selection, natural selection, allometry, and phylogenetic inertia. In this paper, each of these hypotheses is examined for its usefulness in explaining the inter‐specific variation in sexual size dimorphism among prosimian primates. Data on body weight and the degree of sexual dimorphism were obtained for 32 prosimian and 95 simian species. Although prosimians exhibited significantly less sexual dimorphism than simians, there was nevertheless significant variation in dimorphism among them. The degree of sexual dimorphism in prosimians did not show significant variance at any taxonomic level, but the majority of variance occurred within genera. Thus, sexual dimorphism in size among prosimians is probably not constrained by phylogeny at the generic level and above. There was no significant correlation between body size and the degree of sexual dimorphism in prosimians, suggesting the absence of an allometric effect. Similarly there was no relationship between body size and sexual dimorphism among simians in this size range. This result suggested that the expression of sexual dimorphism may nevertheless be influenced by absolute size. In prosimians, inter‐specific differences in sexual dimorphism were not correlated with variance in male reproductive success. It is suggested that speed and agility of males, rather than size and strength, might have been favored by intra‐sexual selection in most prosimians. It seems also plausible that the relative monomorphism of most prosimians, especially in the Lemuriformes, might be a result of increased female size favored by natural selection. Consideration of all natural and sexual selective pressures that affect size in both sexes separately is required to understand the adaptive function and evolution of primate size dimorphism.

Body modifications have been prevalent for centuries and are practiced for a great variety of reasons. Lately, tattoos and body piercings have become increasingly popular. Thus, a profound understanding of the underlying motivations behind obtaining tattoos and body piercings nowadays is required. A considerable body of research on motivational aspects already exists, mainly using explorative approaches to describe motivations. In this paper we provide a review of the existing relevant literature. Furthermore, we establish ten broad motivational categories, comprising motivations for getting tattooed and body pierced, for reference in future research.

Abstract The gregarious lemurs of Madagascar show a lack of convergence with anthropoid primates in several social, demographic, morphological and ecological features. They lack sexual dimorphism in canine and body size, and live in groups with equal adult sex ratios that can vary in composition from pairs to larger units. In most species, females dominate males, and have brief and often synchronized estruses. Finally, lemurs are often active during both day and night (i.e. cathemeral). Three hypotheses for this lack of convergence are discussed. The traditional explanation is that Madagascar's unique ecological pressures have forced females to exclude males from access to limiting resources, selecting for the other unique features as means to maintain female dominance over males. This idea is not logically consistent and is also poorly supported empirically. The second hypothesis claims that cathemerality imposes unique constraints on lemur social organization. The social behavior of cathemeral taxa is largely consistent with this idea. However, the social organization of the diurnal species is not. The third hypothesis claims that recent ecological changes, in particular the demise of large diurnal raptors, have produced a mismatch between current activity periods and adaptations to activity period. This idea is supported by a review of morphological adaptations to light conditions among lemurs, and, more generally, by a comparative analysis of cathemerality among tropical forest mammals. We conclude that the social systems of non‐nocturnal lemurs are best considered as groups formed by species adapted to live in pairs. However, we cannot conclusively exclude the possibility that cathemeral activity is an old and stable activity pattern among lemurs. We indicate which data would decide the issue, and discuss the implications for views of social evolution of lemurs and other animals.

Cooperative behavior has been one of the enigmas of evolutionary theory since the days of Charles Darwin. The contributions to this book examine the many facets of cooperative behavior in primates and

Abstract Large‐scale monitoring schemes are essential in assessing global mammalian biodiversity, and in this framework, leeches have recently been promoted as an indirect source of DNA from terrestrial mammal species. Carrion feeding flies are ubiquitous and can be expected to feed on many vertebrate carcasses. Hence, we tested whether fly‐derived DNA analysis may also serve as a novel tool for mammalian diversity surveys. We screened DNA extracted from 201 carrion flies collected in tropical habitats of C ôte d' I voire and M adagascar for mammal DNA using multiple PCR systems and retrieved DNA sequences from a diverse set of species (22 in C ôte d' I voire, four in M adagascar) exploiting distinct forest strata and displaying a broad range of body sizes. Deep sequencing of amplicons generated from pools of flies performed equally well as individual sequencing approaches. We conclude that the analysis of fly‐derived DNA can be implemented in a very rapid and cost‐effective manner and will give a relatively unbiased picture of local mammal diversity. Carrion flies therefore represent an extraordinary and thus far unexploited resource of mammal DNA , which will probably prove useful for future inventories of wild mammal communities.

Speciation begins when populations become genetically separated through a substantial reduction in gene flow, and it is at this point that a genetically cohesive set of populations attain the sole property of species: the independent evolution of a population-level lineage. The comprehensive delimitation of species within biodiversity hotspots, regardless of their level of divergence, is important for understanding the factors that drive the diversification of biota and for identifying them as targets for conservation. However, delimiting recently diverged species is challenging due to insufficient time for the differential evolution of characters--including morphological differences, reproductive isolation, and gene tree monophyly--that are typically used as evidence for separately evolving lineages.In this study, we assembled multiple lines of evidence from the analysis of mtDNA and nDNA sequence data for the delimitation of a high diversity of cryptically diverged population-level mouse lemur lineages across the island of Madagascar. Our study uses a multi-faceted approach that applies phylogenetic, population genetic, and genealogical analysis for recognizing lineage diversity and presents the most thoroughly sampled species delimitation of mouse lemur ever performed.The resolution of a large number of geographically defined clades in the mtDNA gene tree provides strong initial evidence for recognizing a high diversity of population-level lineages in mouse lemurs. We find additional support for lineage recognition in the striking concordance between mtDNA clades and patterns of nuclear population structure. Lineages identified using these two sources of evidence also exhibit patterns of population divergence according to genealogical exclusivity estimates. Mouse lemur lineage diversity is reflected in both a geographically fine-scaled pattern of population divergence within established and geographically widespread taxa, as well as newly resolved patterns of micro-endemism revealed through expanded field sampling into previously poorly and well-sampled regions.

This paper introduces a Theme Issue presenting the latest developments in research on the interplay between flexibility and constraint in social behaviour, using comparative datasets, long-term field studies and experimental data from both field and laboratory studies of mammals. We first explain our focus on mammals and outline the main components of their social systems, focusing on variation within- and among-species in numerous aspects of social organization, mating system and social structure. We then review the current state of primarily ultimate explanations of this diversity in social behaviour. We approach the question of how and why the balance between behavioural flexibility and continuity is achieved by discussing the genetic, developmental, ecological and social constraints on hypothetically unlimited behavioural flexibility. We introduce the other contributions to this Theme Issue against this background and conclude that constraints are often crucial to the evolution and expression of behavioural flexibility. In exploring these issues, the enduring relevance of Tinbergen's seminal paper 'On aims and methods in ethology', with its advocacy of an integrative, four-pronged approach to studying behaviour becomes apparent: an exceptionally fitting tribute on the 50th anniversary of its publication.

Behavioural and cognitive processes play important roles in mediating an individual's interactions with its environment. Yet, while there is a vast literature on repeatable individual differences in behaviour, relatively little is known about the repeatability of cognitive performance. To further our understanding of the evolution of cognition, we gathered 44 studies on individual performance of 25 species across six animal classes and used meta-analysis to assess whether cognitive performance is repeatable. We compared repeatability (R) in performance (1) on the same task presented at different times (temporal repeatability), and (2) on different tasks that measured the same putative cognitive ability (contextual repeatability). We also addressed whether R estimates were influenced by seven extrinsic factors (moderators): type of cognitive performance measurement, type of cognitive task, delay between tests, origin of the subjects, experimental context, taxonomic class and publication status. We found support for both temporal and contextual repeatability of cognitive performance, with mean R estimates ranging between 0.15 and 0.28. Repeatability estimates were mostly influenced by the type of cognitive performance measures and publication status. Our findings highlight the widespread occurrence of consistent inter-individual variation in cognition across a range of taxa which, like behaviour, may be associated with fitness outcomes.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Adult sex ratio (ASR) is a central concept in population demography and breeding system evolution, and has implications for population viability and biodiversity conservation. ASR exhibits immense interspecific variation in wild populations, although the causes of this variation have remained elusive. Using phylogenetic analyses of 187 avian species from 59 families, we show that neither hatching sex ratios nor fledging sex ratios correlate with ASR. However, sex-biased adult mortality is a significant predictor of ASR, and this relationship is robust to 100 alternative phylogenetic hypotheses, and potential ecological and life-history confounds. A significant component of adult mortality bias is sexual selection acting on males, whereas increased reproductive output predicts higher mortality in females. These results provide the most comprehensive insights into ASR variation to date, and suggest that ASR is an outcome of selective processes operating differentially on adult males and females. Therefore, revealing the causes of ASR variation in wild populations is essential for understanding breeding systems and population dynamics.

Classic theories of ageing consider extrinsic mortality (EM) a major factor in shaping longevity and ageing, yet most studies of functional ageing focus on species with low EM. This bias may cause overestimation of the influence of senescent declines in performance over condition-dependent mortality on demographic processes across taxa. To simultaneously investigate the roles of functional senescence (FS) and intrinsic, extrinsic and condition-dependent mortality in a species with a high predation risk in nature, we compared age trajectories of body mass (BM) in wild and captive grey mouse lemurs (Microcebus murinus) using longitudinal data (853 individuals followed through adulthood). We found evidence of non-random mortality in both settings. In captivity, the oldest animals showed senescence in their ability to regain lost BM, whereas no evidence of FS was found in the wild. Overall, captive animals lived longer, but a reversed sex bias in lifespan was observed between wild and captive populations. We suggest that even moderately condition-dependent EM may lead to negligible FS in the wild. While high EM may act to reduce the average lifespan, this evolutionary process may be counteracted by the increased fitness of the long-lived, high-quality individuals.

Abstract Implementation of the coalescent model in a Bayesian framework is an emerging strength in genetically based species delimitation studies. By providing an objective measure of species diagnosis, these methods represent a quantitative enhancement to the analysis of multilocus data, and complement more traditional methods based on phenotypic and ecological characteristics. Recognized as two species 20 years ago, mouse lemurs (genus Microcebus ) now comprise more than 20 species, largely diagnosed from mt DNA sequence data. With each new species description, enthusiasm has been tempered with scientific scepticism. Here, we present a statistically justified and unbiased Bayesian approach towards mouse lemur species delimitation. We perform validation tests using multilocus sequence data and two methodologies: (i) reverse‐jump Markov chain Monte Carlo sampling to assess the likelihood of different models defined a priori by a guide tree, and (ii) a Bayes factor delimitation test that compares different species‐tree models without a guide tree. We assess the sensitivity of these methods using randomized individual assignments, which has been used in bpp studies, but not with Bayes factor delimitation tests. Our results validate previously diagnosed taxa, as well as new species hypotheses, resulting in support for three new mouse lemur species. As the challenge of multiple researchers using differing criteria to describe diversity is not unique to Microcebus , the methods used here have significant potential for clarifying diversity in other taxonomic groups. We echo previous studies in advocating that multiple lines of evidence, including use of the coalescent model, should be trusted to delimit new species.

Phylogeographic analysis can be described as the study of the geological and climatological processes that have produced contemporary geographic distributions of populations and species. Here, we attempt to understand how the dynamic process of landscape change on Madagascar has shaped the distribution of a targeted clade of mouse lemurs (genus Microcebus ) and, conversely, how phylogenetic and population genetic patterns in these small primates can reciprocally advance our understanding of Madagascar's prehuman environment. The degree to which human activity has impacted the natural plant communities of Madagascar is of critical and enduring interest. Today, the eastern rainforests are separated from the dry deciduous forests of the west by a large expanse of presumed anthropogenic grassland savanna, dominated by the Family Poaceae, that blankets most of the Central Highlands. Although there is firm consensus that anthropogenic activities have transformed the original vegetation through agricultural and pastoral practices, the degree to which closed-canopy forest extended from the east to the west remains debated. Phylogenetic and population genetic patterns in a five-species clade of mouse lemurs suggest that longitudinal dispersal across the island was readily achieved throughout the Pleistocene, apparently ending at ∼55 ka. By examining patterns of both inter- and intraspecific genetic diversity in mouse lemur species found in the eastern, western, and Central Highland zones, we conclude that the natural environment of the Central Highlands would have been mosaic, consisting of a matrix of wooded savanna that formed a transitional zone between the extremes of humid eastern and dry western forest types.

The intestinal microbiota plays a major role in host development, metabolism, and health. To date, few longitudinal studies have investigated the causes and consequences of microbiota variation in wildlife, although such studies provide a comparative context for interpreting the adaptive significance of findings from studies on humans or captive animals. Here, we investigate the impact of seasonality, diet, group membership, sex, age, and reproductive state on gut microbiota composition in a wild population of group-living, frugi-folivorous primates, Verreaux's sifakas (Propithecus verreauxi). We repeatedly sampled 32 individually recognizable animals from eight adjacent groups over the course of two different climatic seasons. We used high-throughput sequencing of the 16S rRNA gene to determine the microbiota composition of 187 fecal samples. We demonstrate a clear pattern of seasonal variation in the intestinal microbiota, especially affecting the Firmicutes-Bacteroidetes ratio, which may be driven by seasonal differences in diet. The relative abundances of certain polysaccharide-fermenting taxa, for example, Lachnospiraceae, were correlated with fruit and fiber consumption. Additionally, group membership influenced microbiota composition independent of season, but further studies are needed to determine whether this pattern is driven by group divergences in diet, social contacts, or genetic factors. In accordance with findings in other wild mammals and primates with seasonally fluctuating food availability, we demonstrate seasonal variation in the microbiota of wild Verreaux's sifakas, which may be driven by food availability. This study adds to mounting evidence that variation in the intestinal microbiota may play an important role in the ability of primates to cope with seasonal variation in food availability.

<h2>Summary</h2> Parasites are sometimes capable of inducing phenotypic changes in their hosts to improve transmission [1]. <i>Toxoplasma gondii</i>, a protozoan that infects a broad range of warm-blooded species, is one example that supports the so-called 'parasite manipulation hypothesis': it induces modifications in rodents' olfactory preferences, converting an innate aversion for cat odor into attraction and probably favoring trophic transmission to feline species, its only definitive hosts [2]. In humans, <i>T. gondii</i> induces behavioral modifications such as personality changes, prolonged reaction times and decreased long-term concentration [3]. However, modern humans are not suitable intermediate hosts because they are no longer preyed upon by felines. Consequently, behavioral modifications in infected people are generally assumed to be side effects of toxoplasmosis or residual manipulation traits that evolved in appropriate intermediate hosts. An alternative hypothesis, however, states that these changes result from parasite manipulative abilities that evolved when human ancestors were still under significant feline predation [3,4]. As such, <i>T. gondii</i> also alters olfactory preferences in humans; infected men rate cat urine, but not tiger urine, as pleasant while non-infected men do not [5]. To unravel the origin of <i>Toxoplasma</i>-induced modifications in humans, we performed olfactory tests on a living primate still predated by a feline species. We found in our closest relative, the chimpanzee (<i>Pan troglodytes troglodytes</i>), that <i>Toxoplasma</i>-infected (TI) animals lost their innate aversion towards the urine of leopards (<i>Panthera pardus</i>), their only natural predator. By contrast, we observed no clear difference in the response of TI and <i>Toxoplasma-</i>non-infected (TN) animals towards urine collected from other definitive feline hosts that chimpanzees do not encounter in nature. Although the adaptive value of parasitically induced behavior should be assessed carefully, we suggest that the behavioral modification we report could increase the probability of chimpanzee predation by leopards for the parasite's own benefit. This possible parasite adaptation would hence suggest that <i>Toxoplasma</i>-induced modifications in modern humans are an ancestral legacy of our evolutionary past.

Variation in communicative complexity has been conceptually and empirically attributed to social complexity, with animals living in more complex social environments exhibiting more signals and/or more complex signals than animals living in simpler social environments. As compelling as studies highlighting a link between social and communicative variables are, this hypothesis remains challenged by operational problems, contrasting results, and several weaknesses of the associated tests. Specifically, how to best operationalize social and communicative complexity remains debated; alternative hypotheses, such as the role of a species’ ecology, morphology, or phylogenetic history, have been neglected; and the actual ways in which variation in signaling is directly affected by social factors remain largely unexplored. In this review, we address these three issues and propose an extension of the “social complexity hypothesis for communicative complexity” that resolves and acknowledges the above factors. We specifically argue for integrating the inherently multimodal nature of communication into a more comprehensive framework and for acknowledging the social context of derived signals and the potential of audience effects. By doing so, we believe it will be possible to generate more accurate predictions about which specific social parameters may be responsible for selection on new or more complex signals, as well as to uncover potential adaptive functions that are not necessarily apparent from studying communication in only one modality. Animals exhibit an astonishing diversity of communicative systems, with important variation in both the nature and the number of signals they produce. The roles of phylogenetic history, genetic drift, environmental factors, and sexual selection in shaping interspecific variation in communicative systems have long been acknowledged, whereas social complexity has only more recently emerged as a potential fundamental factor determining signal diversification. While a number of comparative studies support the key prediction of this hypothesis, i.e., that individuals living in more complex social environments exhibit more signals and/or more complex signals, we discuss several gaps in the current state of the art concerning this hypothesis and point out what we believe are neglected perspectives. By emphasizing the importance of the multimodal nature of communicative systems and the social context in which signals are exchanged, we hope to stimulate the development of new tests and specific questions based on this expanded framework.

Abstract Threats to biodiversity are well documented. However, to effectively conserve species and their habitats, we need to know which conservation interventions do (or do not) work. Evidence-based conservation evaluates interventions within a scientific framework. The Conservation Evidence project has summarized thousands of studies testing conservation interventions and compiled these as synopses for various habitats and taxa. In the present article, we analyzed the interventions assessed in the primate synopsis and compared these with other taxa. We found that despite intensive efforts to study primates and the extensive threats they face, less than 1% of primate studies evaluated conservation effectiveness. The studies often lacked quantitative data, failed to undertake postimplementation monitoring of populations or individuals, or implemented several interventions at once. Furthermore, the studies were biased toward specific taxa, geographic regions, and interventions. We describe barriers for testing primate conservation interventions and propose actions to improve the conservation evidence base to protect this endangered and globally important taxon.

Abstract Accurately quantifying species’ area requirements is a prerequisite for effective area‐based conservation. This typically involves collecting tracking data on species of interest and then conducting home‐range analyses. Problematically, autocorrelation in tracking data can result in space needs being severely underestimated. Based on the previous work, we hypothesized the magnitude of underestimation varies with body mass, a relationship that could have serious conservation implications. To evaluate this hypothesis for terrestrial mammals, we estimated home‐range areas with global positioning system (GPS) locations from 757 individuals across 61 globally distributed mammalian species with body masses ranging from 0.4 to 4000 kg. We then applied block cross‐validation to quantify bias in empirical home‐range estimates. Area requirements of mammals &lt;10 kg were underestimated by a mean approximately15%, and species weighing approximately100 kg were underestimated by approximately50% on average. Thus, we found area estimation was subject to autocorrelation‐induced bias that was worse for large species. Combined with the fact that extinction risk increases as body mass increases, the allometric scaling of bias we observed suggests the most threatened species are also likely to be those with the least accurate home‐range estimates. As a correction, we tested whether data thinning or autocorrelation‐informed home‐range estimation minimized the scaling effect of autocorrelation on area estimates. Data thinning required an approximately93% data loss to achieve statistical independence with 95% confidence and was, therefore, not a viable solution. In contrast, autocorrelation‐informed home‐range estimation resulted in consistently accurate estimates irrespective of mass. When relating body mass to home range size, we detected that correcting for autocorrelation resulted in a scaling exponent significantly &gt;1, meaning the scaling of the relationship changed substantially at the upper end of the mass spectrum.

Is it possible to slow the rate of ageing, or do biological constraints limit its plasticity? We test the 'invariant rate of ageing' hypothesis, which posits that the rate of ageing is relatively fixed within species, with a collection of 39 human and nonhuman primate datasets across seven genera. We first recapitulate, in nonhuman primates, the highly regular relationship between life expectancy and lifespan equality seen in humans. We next demonstrate that variation in the rate of ageing within genera is orders of magnitude smaller than variation in pre-adult and age-independent mortality. Finally, we demonstrate that changes in the rate of ageing, but not other mortality parameters, produce striking, species-atypical changes in mortality patterns. Our results support the invariant rate of ageing hypothesis, implying biological constraints on how much the human rate of ageing can be slowed.

In species with separate sexes, females and males often differ in their morphology, physiology and behaviour. Such sex-specific traits are functionally linked to variation in reproductive competition, mate choice and parental care, which have all been linked to sex roles. At the 150th anniversary of Darwin's theory on sexual selection, the question of why patterns of sex roles vary within and across species remains a key topic in behavioural and evolutionary ecology. New theoretical, experimental and comparative evidence suggests that variation in the adult sex ratio (ASR) is a key driver of variation in sex roles. Here, we first define and discuss the historical emergence of the sex role concept, including recent criticisms and rebuttals. Second, we review the various sex ratios with a focus on ASR, and explore its theoretical links to sex roles. Third, we explore the causes, and especially the consequences, of biased ASRs, focusing on the results of correlational and experimental studies of the effect of ASR variation on mate choice, sexual conflict, parental care and mating systems, social behaviour, hormone physiology and fitness. We present evidence that animals in diverse societies are sensitive to variation in local ASR, even on short timescales, and propose explanations for conflicting results. We conclude with an overview of open questions in this field integrating demography, life history and behaviour.

Among pair-living species, which represent a simple form of gregariousness, the degree of cohesion appears to be highly variable, but the mechanisms responsible for the maintenance of cohesiveness have been poorly studied. We present data from long-term behavioural observations of eight pairs of fork-marked lemurs, including year-round data on their sleeping site use and spatial data from simultaneous focal follows of both pair partners, that characterize its social organization as 'dispersed pairs'. Although pairs were stable over several years, territories of pair partners overlapped almost perfectly and interactions between them were frequent, the cohesiveness of pairs was extremely low. High rates of conflict relative to frequencies of affiliative interactions indicated that avoidance of the pair partner is the key mechanism responsible for the observed pattern of space use. The repeated use of the same predictable food resources during the night, frequent conflicts over food and patterns of vocal communication imply that avoidance of direct feeding competition, together with incomplete knowledge about the pair partner's position, lead to the observed low cohesiveness. The freedom to forage solitarily and the associated lack of information about the pair partner's position found in fork-marked lemurs are in contrast to most group-living species and qualify dispersed pairs as a focus for future studies of models on animal movement decisions. Copyright 2003 The Association for the Study of Animal Behaviour. Published by Elsevier Science Ltd. All rights reserved.

The main objective of this study was to investigate two predictions of sexual selection theory concerning interspecific variation in testis size among strepsirhine primates (Lemuriformes and Lorisiformes). First, the unique evolutionary history of lemurs provides an opportunity for an independent test of the predictions of sperm competition theory regarding the relationship between mating system and relative testis size. Second, I examined the evolutionary relationship between the morphological correlates of pre- and postcopulatory competition (i.e., between sexual dimorphism and testis size) because polygamous lemurs, in contrast to other polygamous primates, lack sexual dimorphism. Based on measurements from 174 captive strepsirhines from 24 species, I found that multi-male species had significantly larger testes than pair-living ones, but that they did not differ significantly from solitary species. This result deviates from theoretical expectations, but may be the result of yet-unknown heterogeneity in mechanisms of male-male competition in both multi-male and solitary species. There was no difference in relative testis size between nonmonogamous lemurs and lorises, indicating that presumably lower levels of precopulatory competition are not necessarily compensated by more intense sperm competition. Body size and phylogenetic effects were also found to considerably affect interspecific variability in testis size. Analyses of independent contrasts revealed that evolutionary changes in mating system, testis size, sexual size, and canine dimorphism were not, or only weakly, associated in this monophyletic group of primates. Additional comprehensive comparative studies of sexual dimorphism, testis size, mating system, and copulatory behavior in these and other taxa are indicated to illuminate general patterns and causes of covariation among these traits

In contrast to most anthropoid primates, sifakas (Propithecus verreauxi), like many group-living lemurs, exhibit a number of features that deviate from predictions of sexual selection theory. Despite a promiscuous mating system, they lack sexual dimorphism, suggesting that physical combat plays only a minor role in intrasexual competition for receptive females. In this study, we investigated the hypothesis that socioendocrinological mechanisms contribute to suppression of reproductive function of subordinate males. For that purpose, 10 male sifakas from five social groups were observed for 669 focal animal hours for 4 months, including the mating season, in Western Madagascar. Concomitantly, 315 fecal samples of these animals were collected and the concentration of immunoreactive testosterone was quantified by enzymeimmunoassay procedures. Clear dominance relationships existed among coresident males. Testosterone levels of dominant males were significantly higher than those of subordinates during, as well as outside, the mating season. Additionally, the increase in testosterone levels prior to the mating season was more pronounced for dominant than for subordinate males. These findings are in accordance with the hypothesis of suppression of sexual function of subordinate males, probably providing dominant males with an advantage in sperm competition. If reproductive success is mainly determined by this nonagonistic form of intrasexual competition, the results of this study contribute an important piece to the puzzle of lacking sexual dimorphism in P. verreauxi.

Abstract Affinitive contact between former opponents soon after a conflict has been demonstrated in a growing number of primate species. Several recent studies show that such contact reduces the probability of future conflicts, allows the recipient of aggression to reduce its anxiety, and restores tolerance between former opponents. Hence, these contacts can be termed reconciliation. In this paper, we critically discuss common methodological problems of studying reconciliation, examine functional aspects, and evaluate the existing variation in primate reconciliation in light of predictions derived from four untested hypotheses about its evolutionary origins. We find that the occurrence of reconciliation in primates is not limited to anthropoids. Neither is it limited to species with formalized dominance relations. Reconciliation is also not a prerequisite for life in permanent social groups. Instead, several lines of evidence support the hypothesis that reconciliation serves to maintain valuable social relationships between individuals. We suggest several more specific versions of this hypothesis and discuss reconciliation between kin, mates, and alliance partners, as well as a number of open questions pertaining to the mechanisms, functions and origins of reconciliation among primates.

The goal of this study was to investigate the extent of convergence in four basic life history and socio-ecological traits among the primates of Africa, Asia, South America and Madagascar. The convergence hypothesis predicts that similar abiotic conditions should result in similar adaptations in independent taxa. Because primates offer a unique opportunity among mammals to examine adaptations of independent groups to tropical environments, we collected information on body mass, activity pattern, diet and group size from all genera for quantitative tests of this hypothesis. We revealed a number of qualitative and quantitative differences among the four primate groups, indicating a lack of convergence in these basic aspects of life history and socio-ecology. Our analyses demonstrated that New World primates are on average significantly smaller than primates in other regions and characterized by a lack of species larger than about 10 kg. Madagascar harbours significantly more nocturnal species than the other regions and is home to all but one of the primates with irregular bursts of activity. Asia is the only region with strictly faunivorous primates, but lacks primarily gummivorous ones. The Neotropics are characterized by the absence of primarily folivorous primates. Solitary species are not represented in the New World, whereas solitary and pair-living species make up the majority of Malagasy primates. Lemurs live in significantly smaller groups than other primates, even after controlling for differences in body size. The lack of convergence among the major primate groups is neither primarily due to phylogenetic constraints as a result of founder effects, nor can it be sufficiently explained as a passive consequence of body size differences. However, because the role of adaptive forces, such as interspecific competition, predation or phenology in shaping the observed differences is largely unexplored, we conclude that it is premature to discard the convergence hypothesis without further tests.

Abstract Phylogenetic comparative methods were used to analyze the consequences of sexual selection on canine size and canine size dimorphism in primates. Our analyses of previously published body mass and canine size data revealed that the degree of sexual selection is correlated with canine size dimorphism, as well as with canine size in both sexes, in haplorhine but not in strepsirrhine primates. Consistent with these results, male and female canine size was found to be highly correlated in all primates. Since canine dimorphism and canine size in both sexes in haplorhines were found to be not only related to mating system but also to body size and body size dimorphism (characters which are also subject to or the result of sexual selection), it was not apparent whether the degree of canine dimorphism is the result of sexual selection on canine size itself, or whether canine dimorphism is instead a consequence of selection on body size, or vice versa. To distinguish among these possibilities, we conducted matched‐pairs analyses on canine size after correcting for the effects of body size. These tests revealed significant effects of sexual selection on relative canine size, indicating that canine size is more important in haplorhine male‐male competition than body size. Further analyses showed, however, that it was not possible to detect any evolutionary lag between canine size and body size, or between canine size dimorphism and body size dimorphism. Additional support for the notion of special selection on canine size consisted of allometric relationships in haplorhines between canine size and canine size dimorphism in males, as well as between canine size dimorphism and body size dimorphism. In conclusion, these analyses revealed that the effects of sexual selection on canine size are stronger than those on body size, perhaps indicating that canines are more important than body size in haplorhine male‐male competition. Am J Phys Anthropol, 2006. © 2005 Wiley‐Liss, Inc.

Intense reproductive competition and social instability are assumed to increase concentrations of glucocorticoids and androgens in vertebrates, as a means of coping with these challenges. In seasonally breeding redfronted lemurs (Eulemur fulvus rufus), the mating and the birth season and the associated increased male competition are predicted to pose such reproductive challenges. In this paper, we investigate seasonal variation in hormone excretion in male redfronted lemurs, and examine whether this variation is associated with social or ecological factors. Although dominance status has been shown to affect individual stress levels across many taxa, we predicted no rank-related differences in glucocorticoids for redfronted lemurs because relatively equal costs are associated with both high and low rank positions (based on patterns of rank acquisition/maintenance and threats toward subordinates). Over a 14-month period, we collected behavioral data (1843 focal hours) and 617 fecal samples from 13 redfronted lemur males in Kirindy Forest/Madagascar. We found no general rank-related pattern of testosterone or glucocorticoid excretion in this species. Both hormones were excreted at significantly higher levels during the mating and the birth season, despite social stability during both periods. The elevated mating season levels may be explained by increased within-group reproductive competition during this time and are in line with previous studies of other seasonally reproducing primates. For the birth season increase, we propose that the predictable risk of infanticide in this highly seasonal species affects male gonadal and adrenal endocrine activity. We evaluate alternative social and ecological factors influencing the production of both hormone classes and conclude based on our preliminary investigations that none of them can account for the observed pattern.

Some primate field studies have been on-going for decades, covering significant portions of individual life cycles or even multiple generations. In this volume, leading field workers report on the his

The primates of Madagascar (Lemuriformes) are unusual among mammals in that polygynous species lack sexual dimorphism, and females dominate males socially in most species. Moreover, lemur groups are relatively small and characterized by even adult sex ratios despite the fact that one male should be able to exclude other males from the group. One hypothesis to explain this combination of behavioral, morphological, and demographic traits (the "lemur syndrome") postulates that male–male competition is relaxed and, hence, variance in male reproductive success is low. Reproductive skew theory provides a framework for testing this and several related predictions about lemur social evolution. Specifically, low reproductive skew is also predicted if dominant males or adult females make reproductive concessions to subordinates or if the latter group successfully pursues alternative reproductive tactics. However, suitable data on paternity, demography, and behavior for a conclusive test of these predictions have not been available in the past. In this paper, we show that male reproductive success in ten groups of Verreaux's sifakas (Propithecus verreauxi) was extremely skewed in favor of the dominant male over 9 years. Our genetic analyses also revealed that more than a third of all groups are effectively harem groups because only one male was unrelated to the resident female(s). In groups with two or more non-natal males, the dominant sired 91% of 33 infants. Together, males pursuing one of several alternative reproductive tactics, such as roaming among several groups or immigrating peacefully, sired only 11% of infants. Thus, female sifakas do not control group composition by offering reproductive opportunities to subordinate males as staying incentives, intrasexual selection is not relaxed, and dominant males prevail in a tug-of-war over subordinate males. Because male reproductive skew in sifakas is even more pronounced than in harem-living anthropoids studied to date, intrasexual selection is clearly not relaxed, and the lemur syndrome is more puzzling than ever.

Living in social groups facilitates cross-infection by parasites. However, empirical studies on indirect transmission within wildlife populations are scarce. We investigated whether asynchronous overnight refuge sharing among neighboring sleepy lizards, Tiliqua rugosa, facilitates indirect transmission of its ectoparasitic tick, Amblyomma limbatum. We fitted 18 neighboring lizards with GPS recorders, observed their overnight refuge use each night over 3 months, and counted their ticks every fortnight. We constructed a transmission network to estimate the cross-infection risk based on asynchronous refuge sharing frequencies among all lizards and the life history traits of the tick. Although self-infection was possible, the network provided a powerful predictor of measured tick loads. Highly connected lizards that frequently used their neighbors' refuges were characterized by higher tick loads. Thus, indirect contact had a major influence on transmission pathways and parasite loads. Furthermore, lizards that used many different refuges had lower cross- and self-infection risks and lower tick loads than individuals that used relatively fewer refuges. Increasing the number of refuges used by a lizard may be an important defense mechanism against ectoparasite transmission in this species. Our study provides important empirical data to further understand how indirectly transmitted parasites move through host populations and influence individual parasite loads.

Communication and cognition.- Visual communication: evolution, ecology, and functional mechanisms.- Vocal communication in social groups.- Kin recognition: an overview of conceptual issues, mechanisms and evolutionary theory.- Honeybee cognition.- Individual performance in complex social systems: the greylag goose example.- Conflict and cooperation.- Conflict and conflict resolution in social insects.- Social insects, major evolutionary transitions and multilevel selection.- Cooperation between unrelated individuals - a game theoretic approach.- Group decision-making in animal societies.- Parental care: adjustments to conflict and cooperation.- Sex and reproduction.- The quantitative study of sexual and natural selection in the wild and in the laboratory.- Mate choice and reproductive conflict in simultaneous hermaphrodites.- Extra-pair behaviour.- Extreme polyandry in social Hymenoptera: evolutionary causes and consequences for colony organisation.- Monogynous mating strategies in spiders.- Mating systems, social behaviour and hormones.- Behavioural variation.- The social modulation of behavioural development.- Alternative reproductive tactics and life history phenotypes.- Animal personality and behavioural syndromes.- Social learning and culture in animals.- Levels and mechanisms of behavioural variability.

The systematics and speciation literature is rich with discussion relating to the potential for gene tree/species tree discordance. Numerous mechanisms have been proposed to generate discordance, including differential selection, long-branch attraction, gene duplication, genetic introgression, and/or incomplete lineage sorting. For speciose clades in which divergence has occurred recently and rapidly, recovering the true species tree can be particularly problematic due to incomplete lineage sorting. Unfortunately, the availability of multilocus or “phylogenomic” data sets does not simply solve the problem, particularly when the data are analyzed with standard concatenation techniques. In our study, we conduct a phylogenetic study for a nearly complete species sample of the dwarf and mouse lemur clade, Cheirogaleidae. Mouse lemurs (genus, Microcebus) have been intensively studied over the past decade for reasons relating to their high level of cryptic species diversity, and although there has been emerging consensus regarding the evolutionary diversity contained within the genus, there is no agreement as to the inter-specific relationships within the group. We attempt to resolve cheirogaleid phylogeny, focusing especially on the mouse lemurs, by employing a large multilocus data set. We compare the results of Bayesian concordance methods with those of standard gene concatenation, finding that though concatenation yields the strongest results as measured by statistical support, these results are found to be highly misleading. By employing an approach where individual alleles are treated as operational taxonomic units, we show that phylogenetic results are substantially influenced by the selection of alleles in the concatenation process.

Vomeronasal receptor genes have frequently been invoked as integral to the establishment and maintenance of species boundaries among mammals due to the elaborate one-to-one correspondence between semiochemical signals and neuronal sensory inputs.Here, we report the most extensive sample of vomeronasal receptor class 1 (V1R) sequences ever generated for a diverse yet phylogenetically coherent group of mammals, the tooth-combed primates (suborder Strepsirrhini).Phylogenetic analysis confirms our intensive sampling from a single V1R subfamily, apparently unique to the strepsirrhine primates.We designate this subfamily as V1Rstrep.The subfamily retains extensive repertoires of gene copies that descend from an ancestral gene duplication that appears to have occurred prior to the diversification of all lemuriform primates excluding the basal genus Daubentonia (the aye-aye).We refer to the descendent clades as V1Rstrep-a and V1Rstrep-b.Comparison of the two clades reveals different amino acid compositions corresponding to the predicted ligand-binding site and thus potentially to altered functional profiles between the two.In agreement with previous studies of the mouse lemur (genus, Microcebus), the majority of V1Rstrep gene copies appear to be intact and under strong positive selection, particularly within transmembrane regions.Finally, despite the surprisingly high number of gene copies identified in this study, it is nonetheless probable that V1R diversity remains underestimated in these nonmodel primates and that complete characterization will be limited until high-coverage assembled genomes are available.

Abstract The lemurs of Madagascar (Primates: Lemuriformes) are a monophyletic group that has lived in isolation from other primates for about 50 million years. Lemurs have diversified into species with diverse daily activity patterns and correspondingly different visual adaptations. We assessed the arrangements of retinal cone and rod photoreceptors in six nocturnal, three cathemeral and two diurnal lemur species and quantified different parameters in six of the species. The analysis revealed lower cone densities and higher rod densities in the nocturnal than in the cathemeral and diurnal species. The photoreceptor densities in the diurnal Propithecus verreauxi indicate a less “diurnal” retina than found in other diurnal primates. Immunolabeling for cone opsins showed the presence of both middle‐to‐longwave sensitive (M/L) and shortwave sensitive (S) cones in most species, indicating at least dichromatic color vision. S cones were absent in Allocebus trichotis and Cheirogaleus medius , indicating cone monochromacy. In the Microcebus species, the S cones had an inverse topography with very low densities in the central retina and highest densities in the peripheral retina. The S cones in the other species and the M/L cones in all species had a conventional topography with peak densities in the central area. With the exception of the cathemeral Eulemur species, the eyes of all studied taxa, including the diurnal Propithecus , possessed a tapetum lucidum , a feature only found among nocturnal and crepuscular mammals.

Linking the cognitive performance of wild animals with fitness consequences is crucial for understanding evolutionary processes that shape individual variation in cognition. However, the few studies that have examined these links revealed differing relationships between various cognitive performance measures and fitness proxies. To contribute additional comparative data to this body of research, we linked individual performance during repeated problem-solving and spatial learning ability in a maze with body condition and survival in wild grey mouse lemurs (Microcebus murinus). All four variables exhibited substantial inter-individual variation. Solving efficiency in the problem-solving task, but not spatial learning performance, predicted the magnitude of change in body condition after the harsh dry season, indicating that the ability to quickly apply a newly discovered motor technique might also facilitate exploitation of new, natural food resources. Survival was not linked with performance in both tasks, however, suggesting that mouse lemurs' survival might not depend on the cognitive performances addressed here. Our study is the first linking cognition with fitness proxies in a wild primate species, and our discussion highlights the importance and challenges of accounting for a species' life history and ecology in choosing meaningful cognitive and fitness variables for a study in the wild.This article is part of the theme issue 'Causes and consequences of individual differences in cognitive abilities'.

Animal and human societies exhibit extreme diversity in the size, composition and cohesion of their social units, in the patterning of sex-specific reproductive skew, in the nature of parental care, in the form and frequency of cooperation and in their competitive regime, creating a diversity of socially complex societies. However, there is an ongoing debate about whether social complexity is a real, emergent property of a society or whether it only provides a conceptual framework for studying the diversity and evolution of societies. In this introduction to our topical collection, we identify three areas of current research addressing relevant challenges in the study of social complexity. First, previous studies have suffered from a lack of a common conceptual framework, including shared definitions, and existing measures of social complexity do not acknowledge its multiple components and dimensions. Second, most previous studies have ignored intraspecific variation, and the proximate and ultimate determinants of variation in social complexity, as well as their interactions, remain poorly known. Third, comparative studies of social complexity offer opportunities to explore its biological causes and correlates and but it is frequently difficult to identify the causal relationships involved and the development of general insights has been hampered by conceptual and methodological difficulties. In this paper, we briefly characterize these three challenges and offer guidance to the other contributions to this topical collection on social complexity by placing their key results in the context of these three topics. In this paper, we address the main current challenges in the study of social complexity and combine our brief overview with a synopsis of the other contributions to this topical collection on various aspects of social complexity.

Intergroup conflict is a major evolutionary force shaping animal and human societies. Males and females should, on average, experience different costs and benefits for participating in collective action. Specifically, among mammals, male fitness is generally limited by access to mates whereas females are limited by access to food and safety. Here we analyse sex biases among 72 species of group-living mammals in two contexts: intergroup conflict and collective movements. Our comparative phylogenetic analyses show that the modal mammalian pattern is male-biased participation in intergroup conflict and female-biased leadership in collective movements. However, the probability of male-biased participation in intergroup conflicts decreased and female-biased participation increased with female-biased leadership in movements. Thus, female-biased participation in intergroup conflict only emerged in species with female-biased leadership in collective movements, such as in spotted hyenas and some lemurs. Sex differences are probably attributable to costs and benefits of participating in collective movements (e.g. towards food, water, safety) and intergroup conflict (e.g. access to mates or resources, risk of injury). Our comparative review offers new insights into the factors shaping sex bias in leadership across social mammals and is consistent with the 'male warrior hypothesis' which posits evolved sex differences in human intergroup psychology. This article is part of the theme issue 'Intergroup conflict across taxa'.

Various aspects of sociality can benefit individuals' health. The host social environment and its relative contributions to the host-microbiome relationship have emerged as key topics in microbial research. Yet, understanding the mechanisms that lead to structural variation in the social microbiome, the collective microbial metacommunity of an animal's social network, remains difficult since multiple processes operate simultaneously within and among animal social networks. Here, we examined the potential drivers of the convergence of the gut microbiome on multiple scales among and within seven neighbouring groups of wild Verreaux's sifakas (Propithecus verreauxi) - a folivorous primate of Madagascar.Over four field seasons, we collected 519 faecal samples of 41 animals and determined gut communities via 16S and 18S rRNA gene amplicon analyses. First, we examined whether group members share more similar gut microbiota and if diet, home range overlap, or habitat similarity drive between-group variation in gut communities, accounting for seasonality. Next, we examined within-group variation in gut microbiota by examining the potential effects of social contact rates, male rank, and maternal relatedness. To explore the host intrinsic effects on the gut community structure, we investigated age, sex, faecal glucocorticoid metabolites, and female reproductive state. We found that group members share more similar gut microbiota and differ in alpha diversity, while none of the environmental predictors explained the patterns of between-group variation. Maternal relatedness played an important role in within-group microbial homogeneity and may also explain why adult group members shared the least similar gut microbiota. Also, dominant males differed in their bacterial composition from their group mates, which might be driven by rank-related differences in physiology and scent-marking behaviours. Links to sex, female reproductive state, or faecal glucocorticoid metabolites were not detected.Environmental factors define the general set-up of population-specific gut microbiota, but intrinsic and social factors have a stronger impact on gut microbiome variation in this primate species. Video abstract.

Inequality in the degree of control (or ‘power’) that members of one sex exert over members of the other sex is a pervasive characteristic of mammalian societies, including our own. The study of the drivers of male–female power relationships has been impeded by methodological limitations and a lack of conceptual embedding in theories of sexual conflict, sexual selection and social evolution. Recent evidence challenges long-standing views by showing that (i) power ranges along a continuum from strictly male- to strictly female-dominated animal societies and (ii) intersexual power relationships are not fixed attributes of species. Here we break with dichotomist and static approaches to adopt a dynamic, theory-driven framework that provides a better understanding of the power struggles between the sexes, and how these relate to the social and mating system of a species. In animal societies, control over resources and reproduction is often biased towards one sex. Yet, the ecological and evolutionary underpinnings of male–female power asymmetries remain poorly understood. We outline a comprehensive framework to quantify and predict the dynamics of male–female power relationships within and across mammalian species. We show that male–female power relationships are more nuanced and flexible than previously acknowledged. We then propose that enhanced reproductive control over when and with whom to mate predicts social empowerment across ecological and evolutionary contexts. The framework explains distinct pathways to sex-biased power: coercion and male-biased dimorphism constitute a co-evolutionary highway to male power, whereas female power emerges through multiple physiological, morphological, behavioural, and socioecological pathways. In animal societies, control over resources and reproduction is often biased towards one sex. Yet, the ecological and evolutionary underpinnings of male–female power asymmetries remain poorly understood. We outline a comprehensive framework to quantify and predict the dynamics of male–female power relationships within and across mammalian species. We show that male–female power relationships are more nuanced and flexible than previously acknowledged. We then propose that enhanced reproductive control over when and with whom to mate predicts social empowerment across ecological and evolutionary contexts. The framework explains distinct pathways to sex-biased power: coercion and male-biased dimorphism constitute a co-evolutionary highway to male power, whereas female power emerges through multiple physiological, morphological, behavioural, and socioecological pathways. trait possessed by an individual at a given time. Intrinsic attributes arise from an individual’s physical, physiological, or cognitive characteristics; social attributes arise from a relationship to others (e.g., social rank, kinship, coalitionary partners). strategy to influence the behaviour of others using some form of physical or psychological pressure, which often involves (the threat of) violence and may incur immediate, direct costs or delayed, indirect costs to the target. mating system where males aggressively defend reproductive access to multiple females. strategy to influence the behaviour of others that consists of withholding information or sharing inaccurate information to increase uncertainty and promote desired behaviour in other individuals. degree of control over resources and reproduction that members of one sex exert over members of the other sex. It shapes – and can thus be measured by – whether and how access to resources and reproduction is gained or retained by individuals of one sex. bargaining asymmetry in the control over the modality of an exchange that arises between trading individuals when one possesses a desirable commodity that cannot be taken by force by others (e.g., skills, information, and under certain conditions, fertilisable eggs). component of a social system that defines the modality of reproduction within a social unit; for example, the average number of mates of males and females, the strategies applied to access mates, the timing and frequency of matings. mating system where a single adult female and a single adult male mate mostly with each other during one or several mating season(s). incentive to engage in potentially costly behaviours or suboptimal trade to gain or retain access to a resource that is shaped by the value attributed to the resource, as determined by the individual state or life history. mating system where individual females commonly mate with multiple males during a single mating season, whereas males do not mate with more than one female. mating system where males and females both are promiscuous and mate with multiple partners during a mating season. mating system where a male can mate with multiple females but each female usually only mates with one male. extent to which an individual can influence the modality of its own reproduction and/or that of others (competitors and potential mates) in terms of the occurrence, timing and frequency of matings, and the number and identity of mates. mating system where females cannot be monopolised by males and male–male competition is mostly noncoercive and postcopulatory. ordinal ranking of individuals belonging to the same social group according to their relative power, typically resource-holding power as derived from the outcome of coercive interactions between pairs of individuals. component of a species social system relating to the demographic composition of a social unit. exchange of commodities between individuals. The modality and expected fitness pay-off of the exchange are shaped by the local socioecological environment.

Abstract Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competition, mate choice, and social interactions. Here we review a growing literature, focusing on methodological developments that sharpen knowledge of the demographic variables underlying ASR variation, experiments that enhance understanding of the consequences of ASR imbalance across societies, and phylogenetic analyses that provide novel insights into social evolution. We additionally highlight areas where research advances are expected to make accelerating contributions across the social sciences, evolutionary biology, and biodiversity conservation.

Seasonal tropical environments are among those regions that are the most affected by shifts in temperature and rainfall regimes under climate change, with potentially severe consequences for wildlife population persistence. This persistence is ultimately determined by complex demographic responses to multiple climatic drivers, yet these complexities have been little explored in tropical mammals. We use long-term, individual-based demographic data (1994 to 2020) from a short-lived primate in western Madagascar, the gray mouse lemur (Microcebus murinus), to investigate the demographic drivers of population persistence under observed shifts in seasonal temperature and rainfall. While rainfall during the wet season has been declining over the years, dry season temperatures have been increasing, with these trends projected to continue. These environmental changes resulted in lower survival and higher recruitment rates over time for gray mouse lemurs. Although the contrasting changes have prevented the study population from collapsing, the resulting increase in life-history speed has destabilized an otherwise stable population. Population projections under more recent rainfall and temperature levels predict an increase in population fluctuations and a corresponding increase in the extinction risk over the next five decades. Our analyses show that a relatively short-lived mammal with high reproductive output, representing a life history that is expected to closely track changes in its environment, can nonetheless be threatened by climate change.

The aim of this review is to summarize newly available information on lemur social systems, to contrast it with the social organization of other primates and to relate it to existing models of primate social evolution. Because of their evolutionary history, the primates of Madagascar constitute a natural experiment in social evolution. During millions of years of isolation, they converged with other primates only in the most fundamental way in the evolution of solitary, pair-living and group-living species, but deviate in several respects within these basic categories of social organization. Solitary lemurs remain poorly studied, but their social organization appears to be broadly similar to that of other solitary primates, even though the unexpected lack of sexual dimorphism may indicate that similar types of social organization can give rise to different mating systems. The determinants of a solitary lifestyle remain elusive. Pair-living lemurs show striking convergences with other monogamous primates in several behavioural traits, but also deviate in that the majority of species are at least partly nocturnal and do not exhibit direct paternal care of dependent young. Group-living lemurs have not evolved single-male groups, male-bonded and multi-level societies, and polyandrous groups may also be lacking. Female philopatry is common, but female bonds are generally weakly developed and eviction of females from natal groups is not unusual. Group-living lemurs also differ from anthropoids in that their groups have even adult sex ratios, smaller average size and may split up on a seasonal basis. Feeding competition, predation risk and reproductive competition can not fully explain these unusual aspects of lemur social organization. It has therefore been suggested that the social consequences of the risk of infanticide and of recent changes in activity may be ultimately responsible for these idiosyncracies of group-living lemurs, an explanation largely supported by the available evidence. Thus, social factors and fundamental life-history traits, in addition to ecological factors, contribute importantly to variation in social systems among lemurs, and possibly other primates. However, neither the diversity of lemur social systems, nor the evolutionary forces and mechanisms operating in these and other primates are yet fully understood.

Abstract The goals of this study were to analyze the origin and function of sex differences in the size of canine teeth among Malagasy lemurs and other strepsirhine primates. These analyses allowed me to illuminate interactions between different mechanisms of sexual selection and to elucidate constraints on this sexually‐selected trait. In contrast to central predictions of sexual selection theory, polygynous lemurs lack both sexual dimorphism in body size and male social dominance, but the degree of sexual dimorphism in the size of their canines is not known. A comparison of male and female canine size in 31 species of lemurs and lorises revealed significant male‐biased canine dimorphism in only 6 of 13 polygynous lemur species. This result is in contrast to predictions of a hypothesis that would explain the lack of size dimorphism in lemurs as a result of high viability costs because canine teeth presumably have low maintenance costs and because they are used as weapons in male‐male combat. Moreover, because females had significantly larger maxillary canines than males in only one lemur species, female dominance is not generally based on female physical superiority and selective forces favoring female dominance do not constrain sexual canine dimorphism in the sense of a pleiotropic effect. Contrary to predictions of sexual selection theory, species differences in canine dimorphism across strepsirhines were neither associated with differences in mating system, nor with the potential frequency of aggression. Variation in canine dimorphism was also unrelated to differences in body size, but there were significant differences among families, pointing to strong phylogenetic constraints. This study demonstrated that polygynous lemurs are at most subject to weak intrasexual selection on dental traits used in male combat and that traits thought to be under intense sexual selection are strongly influenced by phylogenetic factors.

In group-living species, theoretical considerations indicate the existence of a fundamental conflict of interest between the sexes over the adult sex ratio within groups. Females may derive certain benefits from living with many males. Males, in contrast, should generally try to monopolize access to a group of females. Which sex ultimately controls adult group sex ratio is poorly known. We examined this conflict between the sexes in redfronted lemurs, Malagasy primates characterized by an unusual lack of female-biased adult sex ratios. Using various demographic and behavioural data from several groups collected over 6 years, we examined (1) the proximate determinants of this unusual sex ratio, (2) the temporal distribution of female fertile phases within groups as a determinant of male monopolization potential, (3) sources of between-group variation in the adult sex ratio, and (4) possible social benefits of the relatively high number of males for both sexes. Birth and mortality rates were not sex biased and males migrated considerably more frequently than females, providing no proximate explanation for the unusual sex ratio. However, certain life history traits (fast maturation, short interbirth intervals) may ultimately play a role because they act to facilitate joint group transfers of male coalitions. Despite a relatively small female group size and an associated high monopolization potential, female oestrous synchrony may prevent the formation of single-male groups. Reduced male group size seems to be the main predictor of take-over rate, and, thus, infanticide risk, suggesting that both sexes may benefit from the high number of coresident males, thereby considerably defusing the conflict of interest between the sexes.

Mammals that live in seasonal environments may adjust their reproductive cycles to cope with fluctuations in food availability. Because lemurs in Madagascar experience highly seasonal variation in food availability, we examined the effects of fluctuating food availability on body condition and reproduction in one of the larger living species, Verreaux's sifaka (Propithecus verreauxi verreauxi), in the Kirindy Forest of western Madagascar. Seven years of demographic data were combined with an intensive study of 25 individuals over the course of 18 months. In contrast to other populations of Verreaux's sifaka, females were found to have greater body mass than males. Both male and female sifaka exhibited significant losses of body mass and fat during the dry season. Females were more likely to give birth and successfully wean an infant when they had higher body mass during the mating season. They mated during the periods of high and declining food availability, gave birth during the lean season, and then timed mid/late lactation with the period of increasing food availability. Thus, we conclude that sifaka follow the "classic" reproductive strategy (sensu van Schaik and van Noordwijk [Journal of Zoology (London) 206:533-549, 1985]).

Abstract. The post-conflict behaviour of two species of prosimian primates was recorded to examine the effects of agonistic interactions on the subsequent behaviour of former opponents. A total of 125 dyadic agonistic interactions between adults of both species were randomly selected during observations of two social groups of each species. During the 10 min following each agonistic interaction (post-conflict), all social interactions of one of the opponents with all group members, including the former opponent, were recorded and compared with baseline rates established by matched-control observations. In ringtailed lemurs, L. catta, the probability of affinitive interactions between former opponents was not affected by a preceding conflict. In redfronted lemurs, E. fulvus rufus, rates of affinitive interactions between former opponents were significantly above baseline levels in the first 2 min following a conflict, and former opponents were selectively attracted to each other. These post-conflict reunions may function as reconciliations. Significantly larger proportions of undecided conflicts, low-intensity conflicts and conflicts between related redfronted lemurs were reconciled, and victims of aggression were significantly more likely to initiate reconciliation. Neither species showed evidence of consolation, i.e. significantly increased affinitive contact between victims of aggression and third parties during the post-conflict period. Ringtailed lemurs, which have a clear dominance hierarchy and within-group kinship structure, showed a trend toward an increased probability of renewed conflict with former opponents, but not with other group members, during the post-conflict period. They provide the first documented example of a highly social species that appears to lack behavioural mechanisms to cope with the dispersive effects of intra-group aggression. These results demonstrate that reconciliation is not limited to the relatively large-brained anthropoid primates, that reconciliation is not a necessary consequence of group life, and that the occurrence of reconciliation is not limited to species with formalized dominance relations.

The aims of this study were to examine potential causes of variation in fundamental life-history traits and to illuminate their consequences for social behavior in the most primitive living primates. Specifically, I reexamined the claim that life histories of strepsirhine primates (lemurs and lorises) are metabolically constrained and tested the hypothesis that female social dominance, a behavioral idiosyncracy of Malagasy strepsirhines, is the result of unusually high energetic maternal investment in reproduction. I collected data on body mass, brain mass, metabolic rate, and fetal and postnatal litter growth rates for 21 lemur and 13 loris species to examine the relationship between maternal investment and the other variables after controlling for allometric and phylogenetic effects. I found that evolutionary changes in fetal growth rates, relative litter mass, and postnatal growth rates were associated with evolutionary changes in maternal mass but that neither brain size nor metabolic rate were independently correlated with variables reflecting maternal investment. Evolutionary changes in all three variables reflecting maternal investment were positively correlated with one another, however, indicating that they are coadapted, only broadly constrained by body size, and unconstrained by brain size and metabolic rate. Lemurs and lorises were found to have similar postnatal litter growth rates; which reflect the bulk of maternal reproductive investment, indicating that the energetic costs of reproduction did not figure prominently in the evolution of female dominance. The suggested unusual energetic stress of reproducing lemur females is further refuted by qualitative comparison with higher primates and other mammals. Thus, strepsirhine life histories are not narrowly constrained by nonadaptive forces and have no direct consequences for social relations between adult males and females.

Summary Maintenance of group cohesion is of vital importance for group-living species. Individuals therefore need to coordinate their potentially divergent interests to maintain group cohesion. We studied behavioural aspects and mechanisms of coordinated group movements in Verreaux’s sifakas (Propithecus verreauxi), an arboreal Malagasy primate living in small groups. During a field study in Kirindy forest, western Madagascar, we studied the initiation and course of group movements, as well as vocalisations used in this context, in three social groups. We found that both sexes initiated group movements, but females did so more often, lead groups further and enlisted more followers than males. Sex of the leader had no effect on the probability that a group would feed or rest after a successful movement, however. Grumble vocalisations were emitted by both leaders and followers at high rates, both before and during group progressions, but Grumbles uttered just before an individual moved were characterised by a significantly steeper frequency modulation at the beginning of the call and higher call frequencies in both females and males. The results of this study indicated that sifakas, which evolved group-living independently from other primates, converge with many other group-living primates in several fundamental proximate aspects of group coordination and cohesion. In contrast to many other primates, however, sifakas did not use a particular call or other signals to initiate or control group movements.

Females of several species of Old World monkeys and apes exhibit enlarged perineal swellings that include the skin of the anogenital region and rump (see Fig. 5.1). Swellings are normally produced by adult females undergoing ovarian activity and they have stimulated evolutionary biologists since Darwin (1876) to think about their adaptive value and the evolutionary mechanisms responsible for their origin and maintenance. Given the association between sexual swellings and mating activity, it seems likely that some aspect of sexual selection is responsible for the evolution of this exaggerated trait. However, even today the functional significance of exaggerated swellings, as well as the processes responsible for their evolution, remain controversial (Dixson, 1983, 1998; Pagel, 1994, 1995; Radwan, 1995; Wiley & Poston, 1996; Nunn, 1999a; Stallmann & Froehlich, 2000; Domb & Pagel, 2001; Nunn et al., 2001; Domb & Pagel, 2002; Zinner et al., 2002; Snowdon, this volume).

Male excess mortality is widespread among mammals and frequently interpreted as a cost of sexually selected traits that enhance male reproductive success. Sex differences in the propensity to engage in risky behaviours are often invoked to explain the sex gap in survival. Here, we aim to isolate and quantify the survival consequences of two potentially risky male behavioural strategies in a small sexually monomorphic primate, the grey mouse lemur Microcebus murinus : (i) most females hibernate during a large part of the austral winter, whereas most males remain active and (ii) during the brief annual mating season males roam widely in search of receptive females. Using a 10-year capture–mark–recapture dataset from a population of M. murinus in Kirindy Forest, western Madagascar, we statistically modelled sex-specific seasonal survival probabilities. Surprisingly, we did not find any evidence for direct survival benefits of hibernation—winter survival did not differ between males and females. By contrast, during the breeding season males survived less well than females (sex gap: 16%). Consistent with the ‘risky male behaviour’ hypothesis, the period for lowered male survival was restricted to the short mating season. Thus, sex differences in survival in a promiscuous mammal can be substantial even in the absence of sexual dimorphism.

We investigated the social organization of the Australian sleepy lizard, Tiliqua rugosa, by describing the social network of a local population. We attached activity meters and GPS recorders to 21 neighbouring lizards in a semiarid site in South Australia, and monitored their location every 10 min over 3 months (September–December 2007). From over 5000 sets of synchronized location records we calculated distances between all possible dyads of active lizards, and constructed binary social networks based on close associations between individuals. We compared empirical networks with a null model network for spatially structured populations that assumed random movement within lizard home ranges. We showed significantly lower network degree (i.e. fewer cases of individuals associating) in the observed network than in the null model, and deduced avoidance between some individuals. We found the predominant form of social organization was pair living, and, contrary to previous reports, we found pair associations persisted after mating had finished. Thus, the network analysis revealed a cryptic social organization, which cannot be explained by either biparental care or mate guarding, but may instead relate to refuge site distributions, enhanced vigilance or efficient location of mates in subsequent seasons.

Understanding the co-occurrence of ecologically similar species remains a puzzling issue in community ecology. The species-rich mouse lemurs (Microcebus spec.) are distributed over nearly all remaining forest areas of Madagascar with a high variability in species distribution patterns. Locally, many congeneric species pairs seem to co-occur, but only little detailed information on spatial patterns is available. Here, we present the results of an intensive capture-mark-recapture study of sympatric Microcebus berthae and M. murinus populations that revealed small-scale mutual spatial exclusion. Nearest neighbour analysis indicated a spatial aggregation in Microcebus murinus but not in M. berthae. Although the diet of both species differed in proportions of food categories, they used the same food sources and had high feeding niche overlap. Also, forest structure related to the spatial distribution of main food sources did not explain spatial segregation because parts used by each species exclusively did not differ in density of trees, dead wood and lianas. We propose that life history trade-offs that result in species aggregation and a relative increase in the strength of intra-specific over inter-specific competition best explain the observed pattern of co-occurrence of ecologically similar congeneric Microcebus species.

Social grooming is a commonly observed affiliative behaviour in primates. Grooming has been suggested to represent a service in a biological marketplace, exchanged either for grooming or for other social commodities or services. Accordingly, grooming is predicted to be approximately reciprocated within a dyad when no other services are being exchanged, but it should be more asymmetrical if partners have different quantities of other services to offer. We analysed 412 grooming bouts observed in four groups of free-ranging redfronted lemurs to test this prediction. Grooming in this species seems to take place in a highly reciprocal manner because partners usually alternate in the roles of groomer and gromee within a grooming bout. However, within dyads there were asymmetries in the duration of grooming given and received. In both sexes, more grooming was directed from low-ranking towards high-ranking individuals than vice versa, and in males this asymmetry became more pronounced as the number of subordinates per group increased. Grooming in bisexual dyads was generally skewed in favour of males, but patterns of grooming between the sexes were less clear than within the sexes. In addition, aggression occurred at high frequencies between classes of individuals that were characterized by nonreciprocal grooming, suggesting that grooming may serve as a means to reduce aggression in dyads with a high potential for conflicts. Taken together, our results indicate that a strict reciprocation of grooming can be offset by power differentials between partners, where grooming appears to be traded by subordinates in exchange for the tolerance of dominants.

In mammals with female philopatry, co-resident females inevitably compete with each other for resources or reproductive opportunities, thereby reducing the kin-selected benefits of altruism towards relatives. These counteracting forces of cooperation and competition among kin should be particularly pronounced in plurally breeding species with limited alternative breeding opportunities outside the natal group. However, little is still known about the costs of reproductive competition on females' fitness and the victims' potential counter-strategies. Here we summarize long-term behavioural, demographic and genetic data collected on a plurally breeding primate from Madagascar to illuminate mechanisms and effects of female reproductive competition, focusing on forcible eviction and potential reproductive restraint. The main results of our study indicate that females in groups of redfronted lemurs (Eulemur rufifrons) above a critical size suffer from competition from their close relatives: females in larger groups face an increased probability of not giving birth as well as a higher probability of being evicted, especially during the annual mating and birth seasons. Eviction is not predicted by the number of adult females, the number of close female relatives, female age or inter-annual variation in rainfall but only by total group size. Thus, eviction in this species is clearly linked with reproductive competition, it cannot be forestalled by reproductive restraint or having many relatives in the group, and it occurs in the absence of a clear dominance hierarchy. Our study therefore also underscores the notion that potential inclusive fitness benefits from living with relatives may have been generally over-rated and should not be taken for granted.

Evolutionary Anthropology: Issues, News, and ReviewsVolume 19, Issue 2 p. 46-56 IssuesFree Access The utility of reproductive skew models in the study of male primates, a critical evaluation Markus Port, Markus Port [email protected] Markus Port recently finished his Ph.D. on reproductive skew among male redfronted lemurs. During his empirical work, he identified pitfalls in the application of reproductive skew theory, which inspired him to write this articleSearch for more papers by this authorPeter M. Kappeler, Peter M. Kappeler [email protected] Peter Kappeler is Professor of Zoology and Anthropology at the University of Göttingen, Germany. He also heads the Department of Behavioral Ecology and Sociobiology at the German Primate Center. His research interests include sexual selection in primates and the evolution of lemur behaviorSearch for more papers by this author Markus Port, Markus Port [email protected] Markus Port recently finished his Ph.D. on reproductive skew among male redfronted lemurs. During his empirical work, he identified pitfalls in the application of reproductive skew theory, which inspired him to write this articleSearch for more papers by this authorPeter M. Kappeler, Peter M. Kappeler [email protected] Peter Kappeler is Professor of Zoology and Anthropology at the University of Göttingen, Germany. He also heads the Department of Behavioral Ecology and Sociobiology at the German Primate Center. His research interests include sexual selection in primates and the evolution of lemur behaviorSearch for more papers by this author First published: 22 April 2010 https://doi.org/10.1002/evan.20243Citations: 50 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL REFERENCES 1 Kappeler PM. 2000. Primate males: causes and consequences of variaton in group composition. Cambridge: Cambridge University Press. 2 Clutton-Brock TH,Parker GA. 1992. Potential reproductive rates and the operation of sexual selection. Quarterly Rev Biol 67: 437– 456. 3 Trivers RL. 1972. 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Abstract High social rank is expected to incur fitness costs under unstable social conditions. A disruption of the oxidative balance may underlie such effects, but how markers of oxidative stress vary in relation to social rank and stability is unknown. We examined in mandrills whether the mating season characterized by social instability between males (but not between females) affected their oxidative balance differently according to their social rank. Outside the mating season, high-ranking males showed the lowest levels of oxidative damage, while during the mating season, they were the only males to experience increased oxidative damage. In contrast, in females, the mating season increased oxidative stress for all of them, irrespective of their social rank. These results support the hypothesis that the coupling between social rank and social stability is responsible for differential costs in terms of oxidative stress, which may explain inter-individual differences in susceptibility to socially-induced health issues.

Tooth wear in primates is caused by aging and ecological factors. However, comparative data that would allow us to delineate the contribution of each of these factors are lacking. Here, we contrast age-dependent molar tooth wear by scoring percent of dentine exposure (PDE) in two wild African primate populations from Gabonese forest and Kenyan savanna habitats. We found that forest-dwelling mandrills exhibited significantly higher PDE with age than savanna yellow baboons. Mandrills mainly feed on large tough food items, such as hard-shell fruits, and inhabit an ecosystem with a high presence of mineral quartz. By contrast, baboons consume large amounts of exogenous grit that adheres to underground storage organs but the proportion of quartz in the soils where baboons live is low. Our results support the hypothesis that not only age but also physical food properties and soil composition, particularly quartz richness, are factors that significantly impact tooth wear. We further propose that the accelerated dental wear in mandrills resulting in flatter molars with old age may represent an adaptation to process hard food items present in their environment.

Abstract Sexual selection theory suggests that choice for partners carrying dissimilar genes at the major histocompatibility complex ( MHC ) may play a role in maintaining genetic variation in animal populations by limiting inbreeding or improving the immunity of future offspring. However, it is often difficult to establish whether the observed MHC dissimilarity among mates drives mate choice or represents a by‐product of inbreeding avoidance based on MHC ‐independent cues. Here, we used 454‐sequencing and a 10‐year study of wild grey mouse lemurs ( M icrocebus murinus ), small, solitary primates from western M adagascar, to compare the relative importance on the mate choice of two MHC class II genes, DRB and DQB , that are equally variable but display contrasting patterns of selection at the molecular level, with DRB under stronger diversifying selection. We further assessed the effect of the genetic relatedness and of the spatial distance among candidate mates on the detection of MHC ‐dependent mate choice. Our results reveal inbreeding avoidance, along with disassortative mate choice at DRB , but not at DQB . DRB ‐disassortative mate choice remains detectable after excluding all related dyads (characterized by a relatedness coefficient r &gt; 0), but varies slightly with the spatial distance among candidate mates. These findings suggest that the observed deviations from random mate choice at MHC are driven by functionally important MHC genes (like DRB ) rather than passively resulting from inbreeding avoidance and further emphasize the need for taking into account the spatial and genetic structure of the population in correlative tests of MHC ‐dependent mate choice.

Mandrills (Mandrillus sphinx) are enigmatic Old World primates whose social organization and ecology remain poorly known. Previous studies indicated, for example, that groups are composed of only adult females and their young or that several units composed of one adult male and several females make up larger permanent social units. Here, we present the first data on group composition and male ranging patterns from the only habituated wild mandrill group and examine how home range size and daily path length varied with environmental and demographic factors over a 15-month period. Our study site is located in southern Gabon where we followed the group on a daily basis, collecting data on presence, ranging, behavior, and parasite load of its individual members. Throughout the study, the group was made up of about 120 individuals, including several non-natal and natal adult and sub-adult males. One-male units were never observed. The mandrills traveled an estimated 0.44-6.50 km/day in a home range area of 866.7 ha. Exploratory analyses revealed that precipitation, the number of adult males present, and the richness of protozoan parasites were all positively correlated with daily path length. These results clarify the social system of mandrills and provide first insights into the factors that shape their ranging patterns.

Individuals living in groups have to achieve collective action for successful territorial defense. Because conflicts between neighboring groups always involve risks and costs, individuals must base their decision to participate in a given conflict on an evaluation of the trade-off between potential costs and benefits. Since group members may differ in motivation to engage in group encounters, they exhibit different levels of participation in conflicts. In this study, we investigated factors influencing participation in intergroup encounters in Verreaux's sifakas (Propithecus verreauxi), a group-living primate from Madagascar. Over a period of 12 months, we studied eight adjacent sifaka groups in Kirindy Forest. We observed 71 encounters between known neighboring groups in which adult females and males participated equally as often. No individual participated in every encounter, and non-participation occurred more often in larger groups. Females participated less often in encounters when they had dependent infants, presumably to reduce the risk of infanticide. Male participation was influenced by social status: dominant males participated in most encounters, whereas males with fewer opportunities to reproduce participated less often, hence male participation is influenced by the incentive of maintaining access to females. The number of actively participating individuals in the opponent group positively influenced the participation in both sexes. Thus, sifakas seem to decide joining a given encounter opportunistically, most likely based on a combination of individual incentives and the actual circumstance of each encounter, suggesting that the complexity in intergroup relationships appears to be the product of decisions made by each individual group member.Cooperation among group-living animals is often challenged by collective action problems resulting from individual differences in interests in contributing to collective behaviors. Intergroup encounters involve distinguished costs and benefits for each individual despite being in the same social group. Therefore, encounters between groups offer a good opportunity to investigate individual participation in collective action. In this study, we investigate the influence of different incentives on individual participation in intergroup encounters in wild Malagasy primate, Verreaux's sifakas. We propose a novel approach that takes into account the variable circumstances of each conflict, such as the number of individuals fighting in both groups as a predictor for participation. We believe that our study not only provides novel data on wild sifakas, but it also offers new perspectives for the interpretation of intergroup relationships in other taxa.

Theoretical models and empirical studies in various taxa have identified important links between variation in sex roles and the number of adult males and females (adult sex ratio (ASR)) in a population. In this review, I examine these relationships in non-human primates. Because most existing theoretical models of the evolution of sex roles focus on the evolutionary origins of sex-biased behaviour, they offer only a general scaffold for predicting variation in sex roles among and within species. I argue that studies examining sex role variation at these more specific levels need to take social organization into account to identify meaningful levels for the measurement of ASR and to account for the fact that ASR and sex roles mutually influence each other. Moreover, taxon-specific life-history traits can constrain sex role flexibility and impact the operational sex ratio (OSR) by specifying the minimum length of female time outs from reproduction. Using examples from the primate literature, I highlight practical problems in estimating ASR and OSR. I then argue that interspecific variation in the occurrence of indirect forms of paternal care might indeed be linked to variation in ASR. Some studies also indicate that female aggression and bonding, as well as components of inter-sexual relationships, are sensitive to variation in ASR. Thus, links between primate sex roles and sex ratios merit further study, and such studies could prompt the development of more specific theoretical models that make realistic assumptions about taxon-specific life history and social organization. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies’.

This theme issue has highlighted the links between sociality, health and fitness in a broad range of organisms, and with approaches that include field and captive studies of animals, comparative and meta-analyses, theoretical modelling and clinical and psychological studies of humans. In this concluding chapter, we synthesize the results of these diverse studies into some of the key concepts discussed in this issue, focusing on risks of infectious disease through social contact, the effects of competition in groups on susceptibility to disease, and the integration of sociality into research on life-history trade-offs. Interestingly, the studies in this issue both support pre-existing hypotheses, and in other ways challenge those hypotheses. We focus on unexpected results, including a lack of association between ectoparasites and fitness and weak results from a meta-analysis of the links between dominance rank and immune function, and place these results in a broader context. We also review relevant topics that were not covered fully in this theme issue, including self-medication and sickness behaviours, society-level defences against infectious disease, sexual selection, evolutionary medicine, implications for conservation biology and selective pressures on parasite traits. We conclude by identifying general open questions to stimulate and guide future research on the links between sociality, health and fitness.

It is increasingly recognized that the relative proportion of potential mates to competitors in a population impacts a range of sex-specific behaviours and in particular mating and reproduction. However, while the adult sex ratio (ASR) has long been recognized as an important link between demography and behaviour, this relationship remains understudied. Here, we introduce the first inter-disciplinary collection of research on the causes and consequences of variation in the ASR in human and animal societies. This important topic is relevant to a wide audience of both social and biological scientists due to the central role that the relative number of males to females in a population plays for the evolution of, and contemporary variation in, sex roles across groups, species and higher taxa. The articles in this theme issue cover research on ASR across a variety of taxa and topics. They offer critical re-evaluations of theoretical foundations within both evolutionary and non-evolutionary fields, and propose innovative methodological approaches, present new empirical examples of behavioural consequences of ASR variation and reveal that the ASR plays a major role in determining population viability, especially in small populations and species with labile sex determination. This introductory paper puts the contributions of the theme issue into a broader context, identifies general trends across the literature and formulates directions for future research. This article is part of the themed issue ‘Adult sex ratios and reproductive decisions: a critical re-examination of sex differences in human and animal societies'.