Returns of Mexican Freetail Bats Banded in Oklahoma

1. 1. Resident Tadarida brasiliensis cynocephala in New Orleans, Louisiana, on colder days formed denser clusters in more protected areas of the roost. 2. 2. Resistance to hypothermia during cold exposure was least in summer, intermediate in early autumn and greatest in late autumn. 3. 3. In autumn months female bats resisted hypothermia longer than male bats. 4. 4. Length of survival at ambient temperatures of 6–7, 15–16 and 22–25°C increased from autumn through winter, and female bats always lived longer than male bats. 5. 5. Greater resistance to hypothermia and greater survival by Tadarida in cool months are correlated with greater fat stores.

Electrophoretic methods were used to test the hypothesis that migrationally distinct populations of Tadarida brasiliensis are distinct genetically. No fixed allelic differences were found, and genic differentiation among samples was slight. Excessive homozygosity within samples relative to that expected at Hardy-Weinberg equilibrium likely represents the Wahlund effect rather than inbreeding. Genetic relationships among southwestern populations of T. brasiliensis apparently are the result of at least some site tenacity of breeding populations but subsequent intermingling of gene pools in maternity and bachelor colonies.

Abstract Based on site-visits over the past several years to Conner Cave in Major County, Oklahoma, it appears that the large population of Brazilian free-tailed bats that historically used the cave as a maternity site has abandoned the cave. This was one of the northernmost maternity caves in the Great Plains. Previous estimates of the size of the population were several hundred thousand.

Incomplete lineage sorting can genetically link populations long after they have diverged, and will exert a more powerful influence on larger populations. The effects of this stochastic process can easily be confounded with those of gene flow, potentially leading to inaccurate estimates of dispersal capabilities or erroneous designation of evolutionarily significant units (ESUs). We have used phylogenetic, population genetic, and coalescent methods to examine genetic structuring in large populations of a widely dispersing bat species and to test hypotheses concerning the influences of coalescent stochasticity vs. gene flow. The Mexican free-tailed bat, Tadarida brasiliensis mexicana, exhibits variation in both migratory tendency and route over its range. Observations of the species' migratory behaviour have led to the description of behaviourally and geographically defined migratory groups, with the prediction that these groups compose structured gene pools. Here, we used mtDNA sequence analyses coupled with existing information from allozyme, banding, and natural history studies to evaluate hypotheses regarding the relationship between migration and genetic structure. Analyses of molecular variance revealed no significant genetic structuring of behaviourally distinct migratory groups. Demographic analyses were consistent with population growth, although the timing of population expansion events differs between migratory and nonmigratory populations. Hypotheses concerning the role of gene flow vs. incomplete lineage sorting on these data are explored using coalescent simulations. Our study demonstrates the importance of accounting for coalescent stochasticity in formulating phylogeographical hypotheses, and indicates that analyses that do not take such processes into account can lead to false conclusions regarding a species' phylogeographical history.

Regional Distribution and Monitoring of Bats, Especially Species of Conservation Concern, Along the Lower Missouri River in South Dakota. Brandon Terry Bales July 2007 Mist netting, and acoustic surveys for bats were conducted along the Missouri River and it’s tributaries in South Dakota during 2005 and 2006. Seventeen areas were sampled, fifteen of which had not be previous surveyed. One hundred sixty-three bats were captured, representing 7 species. Distribution, morphometric, reproductive, recapture, and capture rate data for the region are presented. As a result Lasiurus cinereus and Lasionycteris noctivagans are likely summer residents in the region, and Myotis ciliolabrum may be present. Species accumulation curves were compiled for eight areas that were repeatedly sampled. Two asymptotic models were fitted to these curves to estimate the effort required to determine bat species richness. The species accumulation models fit capture data well (r > 0.7681). The resulting recommended minimum sampling effort is 284 net-hours: approximately 5 nets set up for 4 hours for 14 nights or 70 net-nights. A minimum-effort guideline is important due to the status of bats, the need for better management, and the pervasiveness of short-term predevelopment surveys by wind energy companies in this region. It is concluded, however, that minimum-effort should not be the goal. Radio-tagging/tracking was also conducted. The roosting

We used thermal imaging to estimate the sizes of the four major Brazilian free-tailed bat (Tadarida brasiliensis) maternity populations in Oklahoma during the summer of 2010 and 2011. The four Oklahoma maternity caves were Merrihew Bat Cave which averaged 66,708 bats, Reed Bat Cave which averaged 165,057 bats, Selman Bat Cave which averaged 54,238 bats, and Vickery Bat Cave which averaged 84,252 bats for all emergences. This study suggests there is a sizable difference in the thermal imaging population size estimates of free-tailed bats at Oklahoma maternity roosts compared to historical estimates using other methods. These differences might be due to the improved accuracy of thermal imaging, or because there is a real decline in bat numbers in Oklahoma, or both.

Abstract Behavioral changes of migratory species have been globally documented in recent decades. However, there is a paucity of research on changes in migratory bat species. Brazilian free-tailed bats (Tadarida brasiliensis) roost in central Texas from March to November. These bats have historically migrated south in late fall, leaving summer roosts unoccupied during winter. Recently, overwintering populations have been discovered in central Texas. The objectives of our study were to determine presence or absence of overwintering free-tailed bats at six known summer roosts, obtain baseline population estimates, and evaluate microclimates of roosts during winters of 2010–2011 and 2011–2012. We used data loggers to monitor temperature and humidity hourly. We estimated population sizes with digital images using ImageJ software, previously established roosting densities, or both. Our results indicated that occupied roosts were colder, had less stable temperatures, and had a stronger correlation between inter...

The natural history of Brazilian free-tailed bats, Tadarida brasiliensis mexicana (Saussure), in an atypical, predominantly male colony in south-central Colorado was investigated in 1982 and 1983. The colony inhabits the Orient Mine at the base of the Sangre de Cristo Mountains in the San Luis Valley. Iron ore was removed from the mine (elevation, 2,800–3,000 m) between 1881 and 1932. Colonization by free-tailed bats occurred no earlier than 1900 and most likely after the mine closed in 1932. The colony roosts in a cavernous underground stope in which ambient temperature varies from 6 to 12°C when bats are present from mid-June through October. At peak numbers, the colony consists of more than 100,000 bats. Outflights in both years lasted an average of nearly 1 h. Bats emerged earlier relative to sunset in late summer and autumn than in early summer. Timing of outflights was not affected by percent cloud cover. Outflights were dispersed in June and became more concentrated, often with serpentine components, later in the year. Capture samples taken with mist nets indicated that composition of the colony was 98% adult males until mid-August, when adult females and young-of-the-year became more common.

The Mexican free-tailed bat, Tadarida brasiliensis mexicana , was noted in environments of 8° to 43°C and relative humidities of 10 to 100%. Large populations of bats usually occurred between 15° and 38°C and 65 to 95% relative humidity. Greatest populations were noted at 25° to 38°C. The temperatures of some Texas caves seem to be influenced by the heat given off by the bats as well as by the outside temperatures. Apparently migration is not directly related to cave temperature. Examination of body temperatures of roosting adult bats throughout the year in ambient temperatures of 12° to 36°C indicated that the subspecies usually regulates its body temperature at high levels in the wild and appears more temperature stable than many Microchiroptera that have been studied. Body temperatures of young bats (from birth until capable of flight) were well above environmental temperatures. Young bats had higher body temperatures as they became older and were at higher ambient temperatures. Regulation of the body temperature at high levels in low environmental temperatures seems to occur by increased heat production, although heat loss is apparently retarded by clustering behavior. Body temperature regulation at high cave temperatures appears to occur in the following ways: The body temperature of the bats remains below that of the deep cluster temperature by virtue of heat loss to the rocks and air which are at lower temperatures. Bats possibly move to cooler sites in the cave in times of heat stress and may separate from one another on the cave ceiling to increase heat loss. By flying and thus greatly increasing the surface area for heat loss the bats seem able to reduce their body temperatures.

Historical events, habitat preferences, and geographic barriers might result in distinct genetic patterns in insular versus mainland populations. Comparison between these two biogeographic systems provides an opportunity to investigate the relative role of isolation in phylogeographic patterns and to elucidate the importance of evolution and demographic history in population structure. Herein, we use a genotype-by-sequencing approach (GBS) to explore population structure within three species of mastiff bats (Molossus molossus, M. coibensis, and M. milleri), which represent different ecological histories and geographical distributions in the genus. We tested the hypotheses that oceanic straits serve as barriers to dispersal in Caribbean bats and that isolated island populations are more likely to experience genetic drift and bottlenecks in comparison with highly connected ones, thus leading to different phylogeographic patterns. We show that population structures vary according to general habitat preferences, levels of population isolation, and historical fluctuations in climate. In our dataset, mainland geographic barriers played only a small role in isolation of lineages. However, oceanic straits posed a partial barrier to the dispersal for some populations within some species (M. milleri), but do not seem to disrupt gene flow in others (M. molossus). Lineages on distant islands undergo genetic bottlenecks more frequently than island lineages closer to the mainland, which have a greater exchange of haplotypes.

Incomplete lineage sorting can genetically link populations long after they have diverged, and will exert a more powerful influence on larger populations. The effects of this stochastic process can easily be confounded with those of gene flow, potentially leading to inaccurate estimates of dispersal capabilities or erroneous designation of evolutionarily significant units (ESUs). We have used phylogenetic, population genetic, and coalescent methods to examine genetic structuring in large populations of a widely dispersing bat species and to test hypotheses concerning the influences of coalescent stochasticity vs. gene flow. The Mexican free-tailed bat, Tadarida brasiliensis mexicana , exhibits variation in both migratory tendency and route over its range. Observations of the species’ migratory behaviour have led to the description of behaviourally and geographically defined migratory groups, with the prediction that these groups compose structured gene pools. Here, we used mtDNA sequence analyses coupled with existing information from allozyme, banding, and natural history studies to evaluate hypotheses regarding the relationship between migration and genetic structure. Analyses of molecular variance revealed no significant genetic structuring of behaviourally distinct migratory groups. Demographic analyses were consistent with population growth, although the timing of population expansion events differs between migratory and nonmigratory populations. Hypotheses concerning the role of gene flow vs. incomplete lineage sorting on these data are explored using coalescent simulations. Our study demonstrates the importance of accounting for coalescent stochasticity in formulating phylogeographical hypotheses, and indicates that analyses that do not take such processes into account can lead to false conclusions regarding a species’ phylogeographical history.