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Brazilian free-tailed bats (Tadarida brasiliensis) emerge from cave roosts in dense columns in which adjacent bats are separated by only small distances. We describe and quantify variation in the structure of echolocation calls produced by these emerging bats and determine if call structure changes in relation to the rate of emergence measured using thermal infrared imaging. We recorded emergence calls at 2 roosts, 1 housing approximately 200,000 bats and the other approximately 17,000 bats. We found that Brazilian free-tailed bats emit distinct frequency-modulated (FMstart) and constant frequency (CFstart) calls during emergence that are significantly different from echolocation calls they emit while foraging. We propose that these calls provide different information for orientation within the emergence column. CFstart calls are very similar to social calls used by Brazilian free-tailed bats, suggesting 2 potential functions for this call type. The structure of both the FMstart and CFstart calls were not related to the number of bats emerging from a roost, although significant structural differences existed between sites. The differences between sites could be associated with the spacing of bats during emergence, because bats appeared to form tighter columns at the larger roost colony compared to the smaller colony. DOI: 10.1644/09-MAMM-A-302.1.

The colony of Brazilian free-tailed bats (Tadarida brasiliensis) at Carlsbad Cavern, New Mexico, is a wellknown example of this highly gregarious and conspicuous species in North America. For nearly a century researchers have tried to estimate the size of this colony, but different census methods and lack of repeatability have resulted in questionable estimates that have given rise to poorly understood but highly popularized, longterm population trends for this migratory species. In this study we present accurate seasonal estimates of colony size based on a recently developed census method—thermal infrared imaging and computer vision analysis. The size of the colony was estimated several times monthly from March through October 2005. Our estimates range from 67,602 to 793,838 bats, values that are orders of magnitude lower than the largest historic estimates. Consecutive estimates of nightly emergences show fluctuations of as many as 291,000 individuals, indicating that colony composition is considerably more dynamic than previously thought. Our results, combined with a quantitative analysis of emergence behavior, question the validity of early historic estimates that millions of bats once roosted in this cave and suggest that the long-term pattern of decline reported for this species might not be as severe as currently thought. DOI: 10.1644/08-MAMM-A-391R.1.

Flexible behaviors permit gregarious animals to exploit spatially and temporally favorable conditions for reproduction. Evening emergences of Brazilian free-tailed bats (Tadarida brasiliensis) in south-central Texas were recorded to determine changes in colony dynamics and to evaluate hypotheses associated with predator avoidance and seasonal energy demands. In 2007, median parturition date was 18 June and lactation lasted about 54 days. Juveniles commenced flight after 41 days, then continued to suckle for 2 weeks before being weaned. Onset of evening emergence was correlated with sunset, beginning, on average, 11.8 min after sunset (95% confidence interval = 7.1, 16.6), which is later than reported in previous studies. Pregnant females emerged later than their roost mates, consistent with a predator avoidance hypothesis. Lactating females emerged after sunset, but earlier than other bats, consistent with the hypothesis that this is a period of high energy demand. Juveniles emerged later than adult females while they continued to be suckled, but emerged earlier as they matured and were weaned, suggesting a trade-off between predator avoidance and energy demands. Our observations indicate that evening emergence behavior of T. brasiliensis varies with environmental cues but is mediated by the energetic demands of reproduction.

Adult males of the long-nosed bat (Leptonycteris curasoae) produce odoriferous ‘‘sebaceous’’ secretions in the interscapular region (dorsal patch), exclusively during the mating season (November–December). These dorsal patches might play a role in mate selection by L. curasoae in northern Venezuela. We evaluated differences between body traits of males with and without dorsal patches to determine whether these structures could be used by females as indicators of male quality, examined whether the size of the dorsal patch shows a relationship with other body traits during the mating season, and investigated the physical and behavioral development of dorsal patches. Thirty-seven percent of all males sampled (n 5 99) showed conspicuous dorsal patches during the mating season in November and December. Males with conspicuous dorsal patches had larger testes, smaller body masses, lower body condition indices, and lower ectoparasite loads than males without dorsal patches. Larger testes and lower ectoparasite loads suggest that the dorsal patch could be signaling male quality and readiness for mating. A typical dorsal patch covered approximately 1.7 cm 2 of a male’s interscapular region, but size of this structure did not vary with any of the body traits examined. We describe a novel, stereotypic behavior performed by male L. curasoae, which we call ‘‘smearing behavior,’’ and suggest that this is associated with development of the dorsal patch because males appear to smear different body fluids onto this patch. We further suggest that sebaceous secretions in the interscapular region would not be the determining factor in dorsal patch development.

Vertebrate mating systems are influenced by ecological and phylogenetic factors, and the variation observed in mating behavior is frequently attributable to the extent to which male assistance in the rearing of offspring increases a female's reproductive rate, size and stability of female groups, and density and distribution of females in space. In this study we evaluate patterns of association and parentage to describe the mating system of the tent-making bat Artibeus watsoni. During 16 consecutive months, we regularly surveyed 2 sites in southwestern Costa Rica and determined size, composition, and stability of social groups, and established patterns of parentage within roosts. We found female-biased, mixed-sex social groups formed by individuals located in several roosts within an area. Roosting associations were low (average across all sites: 31%), and the frequent changes between roosting partners suggests that males and females formed nonexclusive mating bonds, which was further supported by our finding that only 27% of young were sired by the male within a roosting group. Paternal sibships were only observed in 17% of dyads of young roosting together, indicating that few males copulated with >1 female of the roosting group during the mating season. However, paternal sibships were only observed in Golfito, which could be explained by greater group size and stability attributable to lower roost availability. Thus, our findings are consistent with a polygynandrous mating system (2 or several males sharing access to 2 or several females, and vice versa) in which males associated intermittently with females that frequently switched roosts, and where breeding opportunities for males seemed related to the defense of roosts, roosting territories, or both. UCR::Vicerrectoría de Docencia::Ciencias Básicas::Facultad de Ciencias::Escuela de Biología

Using data collected with thermal imaging technology, we found a major reduction in population estimates of colony size in the Brazilian free-tailed bat (Tadarida brasiliensis) from 54 million, obtained in 1957 without this technology, to 4 million in 6 major cave colonies in the southwestern United States. The 1957 census was based on human visual observations of cave emergence flights that were subject to potentially high errors. The recent census was produced using an accurate, reproducible counting method and based on complete temporal records of colony emergences. Analysis of emergence flights from dusk through darkness also revealed patterns in group behavior that would be difficult to capture without thermal infrared technology. Flow patterns of bats during emergence flights exhibited characteristic single, double, or triple episodes, with the peak flow during the 1st episode. A consistent rhythmic pattern of flow episodes and pauses was revealed across colonies and was independent of emergence tempo.

Niche theory predicts that coexisting species should differ ecologically, morphologically, or behaviorally in ways that minimize competition. We used an ecomorphological approach to determine how coexisting species in the Old World fruit bat genus, Cynopterus, assort in morphological and ecological space. The study was conducted in peninsular Malaysia where 4 species of Cynopterus are broadly sympatric. Interspecific separation in resource use was estimated along 3 main axes: habitat, based on abundance across a habitat gradient at 2 sites; trophic niche, inferred from a suite of cranial and postcranial characters; and locomotory behavior and efficiency, inferred from wing morphology. Habitat associations, overall size, and the size and shape of the trophic apparatus were all important in separating 2 or more species, whereas interspecific differences in wing morphology were minor. In combination, the results of this study suggest that relatively minor separation among Cynopterus species pairs along single axes of resource use is sufficient to counteract overlap on other axes, and permit the coexistence of potential competitors.

When minerals are deficient in the diet, animals often seek out concentrated sources of essential nutrients to relieve deficiencies. In this study, we documented fruit bat (Pteropus tonganus) preference or avoidance of calcium-rich fruits and use of commercial calcium blocks to obtain additional calcium. Individual captive wildcaught bats were videotaped nightly to document food choice, and results were compared to the nutritional content of the given fruits. Low-calcium, high-sugar fruits were the most preferred by bats of both sexes. Overall, sugar appears to be the primary basis for fruit selection, but sex differences in calcium block use suggest that females also may forage to relieve calcium deficiencies incurred by pregnancy and lactation. Diets of wild animals can be low in essential nutrients. When minerals are deficient in the diet, animals often seek out concentrated sources of these nutrients. These sources may include natural mineral licks and foods that are rich in the deficient mineral (Klaus et al. 1998). High sodium concentrations often attract wild animals to mineral licks (Belovsky and Jordan 1981; Tracy and McNaughton 1995), although minerals such as calcium and magnesium may be equally important (Holl and Bleich 1987; Jones and Hanson 1985). When consumed by animals, these concentrated sources of minerals may help com

We describe design of echolocation signals in 5 species of aerial-hawking insectivorous bats from Malaysia. These bats forage in open spaces above the forest or in large clearings and belong to 2 families: Molossidae (Chaerephon johorensis, Mops mops, Cheiromeles torquatus) and Vespertilionidae (Hesperoptenus blanfordi, Pipistrellus stenopterus). As is typical for aerial-hawking bats, all 5 species produced narrowband calls of long duration (6‐21 ms) and low peak frequency (16‐44 kHz). However, sequences recorded from bats flying at high altitude ( .10 m) were characterized by an alternation between calls that differed in frequency of maximum energy (peak frequency), switching between high- and low-frequency calls. In some species, the types of calls also differed in duration and sound pressure level. We consider possible implications of the alternation of types of calls for the detection of prey in open spaces.

Estimates of postnatal growth rates and age based on data collected from free-ranging little brown myotis (Myotis lucifugus) captured sequentially at the same colony in the same year were used to compare longitudinal (mark–recapture) and cross-sectional (grab) sampling methods. Analyses of these data indicate that cross-sectional sampling significantly underestimates growth rates for length of forearm, body mass, and length of epiphyseal gap. Equations based on cross-sectional samples significantly overestimated ages of young, as compared with equations based on the longitudinal method. These results support the hypothesis that cross-sectional sampling is unreliable for deriving postnatal growth curves for free-ranging bats and emphasize the importance of using longitudinal data to derive growth rates and estimates of age during the postnatal period.

We evaluated seasonal dietary variation of the Indian pygmy bat, Pipistrellus mimus , from southern India, by collecting biweekly fecal samples from beneath a maternity roost for 1 year and comparing these samples with insects collected using a light trap on the same dates. Our analyses indicate that P. mimus fed on coleopterans (26.3% volume), dipterans (20.4%), homopterans (17.5%), lepidopterans (13.6%), formicids (10.5%), hemipterans (5.7%), and isopterans (5.1%) and thus are generalized feeders. One unidentified scarabaeid species made up much of the coleopteran material and was abundant in the diet of P. mimus from late April through late August. Formicid alates were consumed throughout the year but were especially important from late July through September. Isopteran alates were important in September and October. Relative proportions of insects that were eaten differed significantly from insects captured in a light trap. In other studies, investigators interpreted such differences as evidence of selection; however, we argue that most insect traps do not provide reliable data on availability and that bats may feed in other areas than where the insects are captured. Our results indicate that >20 fecal pellets are needed in any one sample to determine important dietary items eaten by this species, although this sampling protocol likely overlooks minor food items.

To investigate constraints on males associated with maintenance of harems, we used a time-energy approach to explore the relationship between temporal occupancy of roosts and nightly foraging activity in male and female greater spear-nosed bats, Phyllostomus hastatus. Harem males and females differed significantly in frequency and duration of nightly foraging bouts. Harem males spent less time away from their roost at night and departed and returned more frequently than did other members of the harem. Adult females and one subadult male foraged mostly during the first 2-3 h after sunset. Total time spent foraging by harem males, adult females, and a subadult male, averaged 98, 152, and 115 min per night, respectively. On average, harem males engaged in 7.2 randomly spaced foraging bouts per night, compared with 2.1 bouts for harem females and 2.0 bouts for a subadult male. Field metabolic rate, expressed on a mass-specific basis (ml CO2 g-1 h-1), averaged 3.4 ± 0.69 SD for harem males, 3.0 ± 0.85 for adult females, 1.9 ± 0.08 for a subadult male. These values varied predictably but did not differ significantly. Similarly, daily energetic expenditure, expressed on a whole-animal basis (kJ/day), averaged 168.6 ± 32.5 for harem males and 124.9 ± 38.9 for adult females but did not differ significantly. Because harem males allocate less time to nightly foraging activity compared with adult females, males should have more time and energy available for vigilance at the roost and/or the defense of females.

We measured postnatal changes in wing morphology and flight capability in free-ranging Phyllostomus hastatus (Chiroptera: Phyllostomidae). Area of wing, wingspan, and aspect ratio increased until volancy, while wing loading reached its lowest values at and after weaning. Young began to fly in their 7th week, when wing area, aspect ratio, and wingspan had reached 84, 95, and 89%, respectively, of values for adult females. Foraging time increased as young achieved volancy. Estimates of flight speed and power requirements from theoretical predictions yield flight speeds that are lowest around weaning, power requirements that increase consistently, and a cost of transport that decreases to a constant level at weaning. Thus, wing morphology of young may function to maximize maneuverability and minimize energy requirements during the vulnerable period of first flight. Wing loading of adult females fluctuated greatly with seasonal changes in body mass. Wing loading of nonreproductive females, a factor of their greater wing area and lower body mass, was significantly lower than in males. An upper limit on the ability to accomodate increased mass may affect wing morphology in this species.

We examine how litter mass in bats varies with respect to wing loading, an important aerodynamic aspect of flight. From geometric proportions, litter mass should scale to wing loading by an exponent of three. Conversely, analysis of aerodynamic consequences of carrying extra mass suggests that an exponent significantly less than three would be selectively advantageous. Our results show that Megachiroptera and Microchiroptera differ in the relationship between litter mass and wing loading. Litter mass in megachiropterans scales as expected by geometric proportions, whereas litter mass in microchiropterans, as a group, and for individual families, scales as expected if aerodynamic consequences of flight influence litter mass more than size constraints. Thus, selection pressures on reproductive traits appear to differ between the two suborders of bats.

Levels of nitrogen, sodium, potassium, magnesium, calcium, and iron were determined for suckling young of known-age, lactating Myotis velifer and Tadarida brasiliensis , and milk from T. brasiliensis nursing known-age young. From birth to weaning, relationships of both nutrient concentrations and nutrient accretion to age are similar for both species but differ for each nutrient and generally reach adult concentration by weaning. While total mass of body sodium and potassium reach adult levels in both species well before weaning, levels of other elements do not. Although comparable data are limited, element concentrations in suckling bats are similar to those for other suckling small mammals and nestling birds. Growth requirements for measured nutrients in these bats are lower than published values for rodents. Most mineral nutrients that were measured in milk for T. brasiliensis varied with stage of lactation and were comparable in concentration with milk of other mammals. Using daily accretion of nutrients and their concentrations in milk, we calculated the minimal mass of milk needed to meet growth requirements in suckling T brasiliensis . Among measured nutrients, calcium is the limiting nutritional factor that determines mass of milk needed by suckling young during postnatal growth.

We used doubly labeled water to measure carbon dioxide production and water flux during pregnancy and lactation in free-ranging big brown bats, Eptesicus fuscus. Mean (± SE ) carbon dioxide production was 1,749 ±144 ml/day during pregnancy ( n = 16) and 2,770 ±351 ml/day during lactation ( n = 5). Including estimates of tissue production and milk export, we calculated that the average requirement for assimilated energy was 48.9 and 105.1 kJ/day for pregnant and lactating females, respectively. About 2% of the total energy required during pregnancy was placed into fetal tissue; milk energy accounted for 28% of the energy assimilated during lactation. Daily water flux was 8.47 and 17.07 ml/day for pregnant and lactating females, respectively. We calculated that E. fuscus obtained >66% of its water preformed in the diet, but 20–22% of daily water intake was from drinking. Urinary water was the largest component of water efflux during pregnancy (72%) and lactation (56%); water exported in milk represented 22% of daily water efflux during lactation. Calculated evaporative losses for free-ranging E. fuscus were half those predicted from laboratory measurements.

Intraspecific variation in size at birth, postnatal growth, and survivorship of young mammals may reflect genetic variation, differential investment of mothers, gender of offspring, and environmental factors. We quantified size at birth and postnatal growth in free-ranging Phyllostomus hastatus (Chiroptera: Phyllostomidae) to develop age-predictive equations and examine effects of maternal size and age on size at birth and survivorship of young. There was a positive relationship between body mass of mothers and young; however, we found no relationship between maternal length of forearm or age on size of young at birth or survivorship. Males weighed more than females at birth and gained mass at a faster rate, although we found no significant gender differences at birth in length of forearm or length of total epiphyseal gap. High variation in size at birth and maturity suggests that there may be few environmental or life-history constraints on body size and postnatal growth in P. hastatus .

In a field experiment designed to evaluate dietary variation in Mexican free-tailed bats ( Tadarida brasiliensis mexicand ) we found that lactating females fed largely on coleopter-ans and lygaeid bugs during evening feeding bouts and mostly on moths during morning feeding bouts. These results suggest that interpretations of food habits in this and other species may be biased unless samples from both nightly feeding bouts are included in the analyses. Diets of different individuals during the same feeding bout were strikingly similar, suggesting that lactating females either fed in the same general habitats or that they encountered and preferentially fed on similar prey items among those available. Bats captured upon return from evening feeding bouts produced significantly more fecal pellets than those captured following second feeding bouts. This difference suggests that either more food is eaten in the first feeding bout or, alternatively, highly chitinous insects such as coleopterans and lygaeids contribute more to fecal matter than relatively soft-bodied moths. We found no significant relationship between hardness of prey and number of pellets produced. Individual bats produced an average of 2–3.6 insects/pellet, but no consistent relationship was found between the number of insects eaten and the number of fecal pellets produced. Our analysis indicates that at least five pellets are needed to establish the number of insect taxa (families) consumed by a bat. Results from this study suggests that future research on food habits of insectivorous bats should examine fecal pellets or stomach contents from evening and morning feeding bouts to fully characterize the diet of a given species.

Based on mark-recapture data, we quantified changes in body mass, length of forearm, and lengths of the total, proximal, and distal epiphyseal gaps of individual Mexican free-tailed bats (Tadarida brasiliensis mexicana) from birth to peak lactation. We used these data to develop empirical growth curves, derive growth rates, establish age-predictive equations, and compare growth parameters based on three nonlinear growth models. Length of forearm and body mass of neonates averaged 18.5 mm ? 0.7 (SD) and 3.2 g + 0.3, respectively. Mean body mass of pups increased linearly for the first 3 weeks, by which time they had achieved ca. 80% of the mean postpartum mass of adult females. Thereafter, body mass remained relatively stable until a small decrease in body mass was observed at the beginning of the 6th week when young first began to fly. The growth trajectory of the forearm also was linear for the first 3 weeks, but, thereafter, increased more slowly until average adult dimensions were reached in the 6th week. Length of total epiphyseal gap increased to its maximum size during the first 2 weeks and subsequently decreased in a linear fashion. Secondary centers of ossification appeared in the metacarpal and first phalanx of the fourth digit at ca. 14 days, thus, making it possible to quantify age-related changes in the proximal and distal epiphyseal gaps. The equation for estimating age based on length of the forearm is valid when this dimension is -39 mm, whereas the equation for estimating age based on length of the total epiphyseal gap is valid when length of the forearm is >39 mm. Together, these two equations make it possible to estimate the age of pups from 1 to 42 days of age in T. brasiliensis. Of the three nonlinear growth models (logistic, Gompertz, and von Bertalanffy), the logistic equation provides the best fit to the empirical curves for length of forearm and body mass.

A quantitative method of age determination, based on measurements of the forearm and digital epiphyseal cartilages, is described for Myotis lucifugus . During the linear growth phase of long bones, age can best be predicted from forearm length. After growth of the forearm slows, measurements of epiphyseal cartilages of the fourth metacarpal-phalangeal joint provide reliable age criteria. A linear regression equation predicts ages of young bats on the basis of forearm lengths from 14.4 mm to 33.5 mm (up to 11–12 days), with 95% confidence intervals ranging from ±0.11 to ±0.27 days. A second equation predicts age from length of the epiphyseal gap when forearm length is greater than 33.5 mm, until day 29, when total gap length approaches one mm. Confidence limits for this equation range from ±0.41 to ±0.91 days. No differences in growth rates were found between sexes, years, or colonies. Sequential use of two independent age criteria extends the interval of reliable age determination in M. lucifugus to 4 weeks, and potentially provides a method of predicting age until the time when the metacarpal epiphyseal cartilages are no longer visible (approximately 2 months).

Forty-six Myotis lucifugus were collected in May and June 1974 at a nursery colony in Hillsborough County, New Hampshire, that had been sprayed with DDT and chlordane in August and September 1973. When collected, 27 bats were alive, two were convulsing, and 17 were dead. Brains, carcasses, and milk and masticated insects from stomachs were analyzed for organochlorine insecticides and poly-chlorinated biphenyls (PCB's). Concentrations of chemical residues in brains of surviving bats were compared with those of dead and convulsing bats. These comparisons indicated that DDT was the cause of death. Lethal brain concentrations of DDT in adult females averaged 24.52 parts per million (ppm) and suggested that adult M. lucifugus are approximately twice as sensitive to DDT as are adult laboratory rats and mice. Juvenile bats were about 1.5 times more sensitive than adult bats. Large chemical residues were present in milk. We found a statistically significant relationship between declines in carcass residues in lactating females and uterine regression for six of 10 toxicants. Among juveniles, there were corresponding, significant increases (for nine of 10 toxicants) in carcass levels of residues correlated with increasing age (growth of forearm).

The efficiency of the Tuttle bat trap was tested by analyzing the proportion of bats that were captured, passed through, avoided, and bounced off traps as they departed at dusk from nursery roosts of Myotis lucifugus . Throughout the warm season, capture success usually varied from 30 to 80 percent among three colonies studied, with the highest success occurring at roosts where bats dropped from a crevice directly into the pathway of a trap. The lowest success was achieved where bats departed through a window-size opening. We suspect that most of the differences in trap success observed among colonies reflected the relative flight momentum that bats established before encountering a trap, the angle of encounter, and the opportunities available for avoidance. Traps were biased in favor of capturing juveniles when they first began to fly outside their roost and before they were weaned. Though no bias exists for juvenile sex ratios, other possible biases include those for learning (prior experience), age, and reproductive condition.

Secondary dentin and cementum were studied histologically in 17 known-age (2–8 years) specimens of Myotis lucifugus and M. velifer and in 30 adult specimens of unknown age representing Pteronotus parnellii, Leptonycteris nivalis, Artibeus jamaicensis, Sturnira ludovici , and Desmodus rotundus . Incremental lines in secondary dentin and cementum were highly variable (both between and within individuals) and did not correspond exactly to age although there generally was a loose correlation between number of lines and age. Difficulties in using such histologically recognizable characteristics to determine age are discussed and previous studies of age determination in bats are reviewed. Incremental lines in secondary dentin were associated with changes in direction and shape of dentinal tubules. Chemical and structural alterations in collagenous matrix and ground substance also were implicated in the formation of incremental lines. Incremental changes in cement were related to stress, consequent dental drift, and eruption.

Postnatal growth rates of free-living Eptesicus fuscus were determined by measuring length of forearm, length of the fourth metacarpal-phalangeal epiphyseal gap, and body weight of known-age juveniles. Linear segments of the forearm and epiphyseal gap curves yielded age-predictive regression equations with 95% confidence limits ranging from ±0.3 to 2.5 days and extending up to 43 days of age. Comparison of E. fuscus and Myotis lucifugus growth rates, when adjusted to body size, showed that E. fuscus grows at significantly slower relative rates than M. lucifugus . When litter size is accounted for, however, the rate of production of offspring biomass is relatively greater in E. fuscus .

In karst regions of western Oklahoma and Kansas, Plecotus townsendii is locally ubiquitous but low in density. Natality is low but reproductive effort and preweaning survival of young are comparatively high. Movement data show no consistent pattern of dispersal that would account for a low density. P. townsendii uses nursery roosts that are marginal or uninhabitable for locally sympatric cave-dwelling species. Reproductive success depends on the ability of individuals in small nursery colonies to maintain a high degree of thermal exchange during pregnancy and lactation. This is facilitated by the formation of dense clusters in which metabolic heat is shared directly by body contact. In our judgment, the selection of intrinsically warm nursery sites is essential for reproductive success. In early and late winter most P. townsendii are absent from caves; presumably they occupy alternate roosts and forage on warm evenings. These bats seem to require relatively cold temperatures to hibernate. In autumn and early winter some individuals hibernate singly near cave entrances where ambient temperatures are variable but cool cave rock stabilizes body temperatures. By midwinter, these sites reach subfreezing temperatures and many bats move deep into caves, where they may form clusters. Both sexes lose over half their body weight before spring. Owing to this large weight loss, susceptibility to predation in midwinter, and probable late winter foraging efforts, we suspect substantial winter mortality as the prevailing limiting factor. The relictual nature of populations in the southern plains is made comprehensible by the species' reproductive, dispersal, and hibernating performance. From this ecological performance we infer that P. townsendii occurred across the southern United States during the Wisconsin glaciation, when numerous trees grew on the southern plains and the climate was moist with short, cool summers and long, mild winters. The present isolated taxa use caves as refugia from intolerable post-Pleistocene winters. The small size of P. townsendii populations, rather severe ecological limitations, and high sensitivity to disturbance lead us to conclude that visitation of nurseries by humans could threaten the species' survival in the Great Plains.

A study was conducted on reproduction, growth, and mortality of Eptesicus fuscus in an area of central Kansas where morphological intergradation has been demonstrated between distinctive eastern and western forms. Observations were made on reproductive chronology and the hypothesis was tested that sexual size dimorphism is evident throughout the period of growth. The parturition period was from late May through the middle of June with most young born in the first week of June. Although the number of implanted embryos exceeded the number surviving to birth, the litter size was two. No significant differences in size or weight were evident between males and females in the prenatal period. Postnatal growth rates in linear dimensions were greater for females than for males. Young bats were foraging at the age of 4 weeks by which time the forearm length had reached 86 and 89 per cent of adult size for males and females, respectively. Adult linear size was attained in approximately 70 days. At birth young bats averaged 3.14 grams or approximately 16 per cent of the postpartum weight of females. Weight gains were nearly linear for the first 6 weeks in both sexes. No sex differences in body weight were evident until young bats were weaned, but after this time females gained weight faster than males. Embryonic resorption, accidents, and predation are considered as factors influencing mortality.

Foraging activity of insectivorous bats was studied from April through October in central Iowa. Temporal activity was quantified by recording capture times throughout feeding periods, and spatial patterns were examined by measuring the abundance and diversity of species in three contrasting habitats. Six species, Myotis lucifugus, Myotis keenii, Lasionycteris noctimgans, Eptesicus fuscus, Lasiurus borealis , and Lasiurus cinereus , were characterized by initial periods of foraging occurring within 5 hours after sunset. Myotis keenii and L. noctivagans had distinct secondary periods of activity, but other species showed only minor secondary periods, or complete cessation of activity, following the initial foraging period. The modes of initial and secondary activity of L. noctivagans, L. borealis and L. cinereus showed almost complete displacement and corresponded to peak periods of nocturnal insect activity, suggesting a mechanism by which some insectivorous bats may partition environmental resources. Those species showing overlap in temporal foraging ( M. keenii and L. noctivagans on the one hand, and M. lucifugus, E. fuscus , and L. borealis on the other) may have evolved spatial strategies to reduce competition for resources. Intraspecific foraging patterns of three species examined may reflect resource partitioning or, alternatively, secondary foraging activity owing to different energy demands of young and lactating females.