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Stomach content analysis of 20 pregnant (x body mass=13.4 g) and 18 lactating (x body mass=11.5 g) female Tadarida brasiliensis revealed that the diet, expressed as percent volume, consists largely of lepidopterans, coleopterans, hymenopterans, and dipterans, in decreasing order of importance. We found no significant difference in the diet of pregnant and lactating females when expressed as percent volume. However, when expressed as percent frequency, proportionately more pregnant females fed on lepidopterans, coleopterans, and dipterans than did lactating bats, and proportionately more lactating females fed on hymenopterans. We found no significant differences in the percentages of water, lean dry mass, fat, and energy density in the stomach contents of pregnant and lactating females. Water in stomach contents averaged 62.7% and fat and lean dry mass averaged 22.2% and 15.2%, respectively (expressed as percentage of wet mass); energy density averaged 31.2 kJ g dry mass. This relatively high energy density of stomach contents, as compared to whole insects, can be attributed to the consumption of insects high in fat (especially flying ants) and the abdomens only of moths and beetles (other body parts being discarded). Estimates of nightly food intake increased markedly from mid- to late pregnancy, stabilized or decreased during late pregnancy, and increased again during early to mid-lactation. Average nightly feeding rate doubled from pregnancy to lactation and increased threefold during the first half of lactation. By adjusting our gravimetric estimates of nightly feeding rate upwards by 40% (based on estimates of field metabolic rate), we estimate that the average nightly energy intake of female T. brasiliensis ranges from 57 kJ day in early lactation to 104 kJ day in mid-lactation. These estimates represent nightly feeding rates averaging 39% and 73% of a female's body mass in the period from early to mid-lactation, respectively.

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Ectoparasite host specificity can be influenced by factors such as the degree of host isolation and ectoparasite mobility. Host-site specificity can result from factors such as proximity to mates, competition, and host grooming behaviour. Ectoparasitic bat flies on bats from the Lamanai area of Belize were collected from hosts captured in mist nets to determine host specificity and host-site specificity. Bat grooming behaviour was also recorded and quantified. From 455 bats (25 species in five families), 773 bat flies (32 species in two families) were collected. Of 32 bat fly species, 25 were only found on 1 bat species, 6 were found on 2 species of the same genus, and 1 was found on 2 species of different genera (the latter appearing to be an accidental association). Specificity of the bat flies tended to follow the taxonomy of the bat hosts, not the ecological isolation of the host species, since bat species that often roost in polyspecific groups did not share bat fly species. Mobility of the bat flies was not related to host specificity. Host-site specificity of bat flies occurred for either fur or membrane on the host, and long hind legs and ctenidia appear to be morphological adaptations for living in fur. Bat grooming behaviour was consistent with the assumptions of a simulation model, which suggested that host grooming could be responsible for host-site segregation of bat flies.

1. Many bat species hibernate to conserve energy during winter and like all hibernators they commonly arouse. During these arousals, some bats may undertake activities away from the hibernation site. Systematic ecological studies of the frequency and purpose of winter activity in temperate zone bats of North America are rare and much of the literature involves observations of single individuals or unmarked populations. 2.We review the available literature on winter activity among North American vespertilionid bats to highlight the paucity of data on this subject and to stimulate future research. Due to the lack of repeated, systematic studies on most North American species, the conclusions drawn are general or pertain only to parts of the geographical range of any species. 3. We suggest that winter activity is ubiquitous among temperate zone bats, but the degree and purpose of activity varies greatly between and within species. In general, cave-dwelling bats tend to be relatively inactive compared with tree and foliage roosting bats during winter. 4. Cave-dwelling and tree cavity-dwelling species do not appear to feed, but they do drink and occasionally copulate during the hibernation period. Species that hibernate in foliage or leaf litter are the most active species during winter and may feed and drink throughout winter, although they probably do not copulate because of their solitary nature. 5. We encourage researchers to conduct studies on all aspects of winter activity for North American vespertilionids across wide latitudinal and altitudinal gradients. We suggest studies in the near future be focused on estimating the energetic costs and benefits of winter activity through determination of the frequency and intensity of winter feeding activity and more thorough examinations of movements within and among caves. Studies on common, wideranging species have the potential to illuminate large-scale patterns and differences and should be favoured over studies on rarer species.