Female Bats Research Articles

Mercury concentrations decline with age in the fur of females of an insectivorous terrestrial mammal (Myotis lucifugus)

Methylmercury (MeHg) is a toxic form of mercury that bioaccumulates in organisms and biomagnifies through food webs. MeHg concentrations can be high in aquatic environments, and this puts high trophic-level predators who derive energy originating from aquatic environments at risk of toxic effects. Due to the potential for bioaccumulation of MeHg over an individual's life, the risk of MeHg toxicity may increase as animals age, and this risk may be especially high in species with relatively high metabolic rates. Total mercury (THg) concentrations were measured from the fur of adult female little brown bats (Myotis lucifugus) collected between 2012 and 2017 in Salmonier Nature Park, Newfoundland and Labrador. Using linear mixed-effects models, the effects of age, year, and day of capture on THg concentrations were evaluated and interpreted with AICc and multi-model inference. We expected that THg concentrations would increase with age, and that due to annual summer moulting, individuals captured earlier in the season would have lower THg concentrations than individuals captured later in the season. Contrary to expectations, THg concentrations decreased with age and date of capture did not explain any variation in concentration. Among individuals, there was a negative relationship between the initial THg concentration of an individual and the rate of change in THg concentrations with age. Using a regression analysis, we found evidence of a population-level decline in THg concentrations in fur over the 6-year study period. Overall, the results indicate that adult female bats eliminate enough MeHg from their tissues to affect a decrease in THg concentrations in their fur over time, and that young adults are potentially at the greatest risk of experiencing toxic effects from high MeHg concentrations; this could result in reduced reproductive output, and warrants further research.

Constitutive Innate Immunity of Migrant and Resident Long-Nosed Bats (Leptonycteris yerbabuenae) in the Drylands of Mexico

In contrast to birds, the relationship between migration and immunity has been scarcely studied in bats. We examined how the expression of the humoral portion of the constitutive immunity varied in a bat with partial, sex-biased migration: the lesser long-nosed bat (Leptonycteris yerbabuenae (Phyllostomidae)). The lesser long-nosed bat is a nectarivorous species distributed in the arid and semi-arid regions of North and Central America. We evaluated the bacteria-killing abilities (BKAs) of the plasma of male and female lesser long-nosed bats on the Pacific coast in different periods of the year. Because adult males are resident, they were used to explore the effect of reproductive activity on BKA, and we predicted higher values in mating males (i.e., individuals presenting scrotal testicles and a fresh dorsal patch). In contrast to males, most females migrate to cactus deserts in northern Mexico during pregnancy and lactation, and then return to the dry forests of west-central Mexico to mate. We predicted that the combined effect of breeding and migration would have an adverse effect on BKA; therefore, migratory pregnant and lactating females were expected to exhibit a lower BKA than mating females in west-central Mexico. We compared the BKAs of females captured in October and December in central Mexico, and we predicted that migratory females that had recently arrived in October should exhibit a lower BKA than females captured two months later. In addition, we compared the BKAs between lactating females and young in northern Mexico and predicted lower values in recently born individuals. We found that the BKAs of males were higher in reproductive individuals than in non-reproductive individuals. We found a significant difference in the BKAs between females at the two extremes of their migratory range: the values of pregnant females in Sonora and females in December were higher than those of females captured in October. Finally, we found no difference in BKAs between lactating females and young individuals. Our findings indicate that the basal levels of the innate humoral component are heightened in mating males, that this response is reduced in females that recently returned to their mating grounds, and that the constitutive immunity of young individuals matures early, probably in anticipation of the potential to encounter pathogens during their migration to west-central Mexico.

Reproductive phenologies of phyllostomid bat populations and ensembles from lowland Amazonia.

Natural selection should favor individuals that synchronize energy-demanding aspects of reproductive activity with periods of high resource abundance and predictability, leading to seasonal patterns of reproduction at the population level. Nonetheless, few studies-especially those on bats in the Neotropics-have used rigorous quantitative criteria to distinguish among phenological patterns for different populations from the same habitat or for the same species in different habitats. To explore such issues, we quantified annual patterns of reproduction in male and in female bats from lowland Amazonia (environs of Iquitos, Peru), and did so at the level of populations and ensembles. Five species exhibited unimodal patterns including Artibeus obscurus, A. planirostris, Carollia benkeithi, Phyllostomus hastatus, and Rhinophylla pumilio. Two species (A. lituratus and Glossophaga soricina) evinced bimodal patterns with reproductive peaks separated by patterns of inactivity, whereas four species (C. brevicauda, C. perspicillata, Sturnira lilium, and S. tildae) evinced a bimodal pattern in which peaks in activity occur in tandem, with the first peak generally markedly higher than the second peak. Frugivore, gleaning animalivore, and nectarivore ensembles exhibited bimodal, unimodal, and bimodal reproductive phenologies, respectively. Nonetheless, interannual variation in phenology (i.e., the monthly timing of peaks within a season rather than the number of peaks per year) characterized four (A. obscurus, C. brevicauda, C. perspicillata, and S. lilium) of the eight species and each of the three ensembles (frugivores, gleaning animalivores, and nectarivores) with adequate sampling. Regardless of interspecific variation in strategies, the phenology of reproduction enhances the likelihood that parturition and recruitment of young into the population occurs during the wet season, the period of likely highest resource abundance. Based on a comparison of our results with those from other well-studied bat populations, four species did not exhibit geographic variation in reproductive phenologies (A. obscurus, G. soricina, C. brevicauda, and R. pumilio), whereas three species evinced such geographic variation (A. lituratus, A. planirostris, and C. perspicillata). Climate change will likely alter the seasons and extents of propitious times for reproductive activities, as well as the reliability of proximate cues for initiating reproduction, compromising current reproductive strategies and leading to altered phenological patterns of reproduction or reproductive success, possibly resulting in local extinction of some species.

Morphological criteria for Pipistrellus pygmaeus kidney indicators

At present, there is scientific and practical interest in the study of morphological and physiological features, criteria and tolerance of organs involved in protein metabolism in representatives of the order Chiroptera. Macro- and micrometric indicators of kidneys in soprano pipistrelle (Pipistrellus pygmaeus), as a result of adaptive transformations of the body to habitat conditions in the Bryansk region were studied. The study was conducted in the period from 2011 to 2022, 40 captures were carried out with a total of 481 individuals, of which 100 were selected for further study. On histological preparations of kidneys of soprano pipistrelle (Pipistrellus pygmaeus), morphometry of nephrons, podocyte parameters, nuclear-cytoplasmic ratio, areas of nucleolar organizers and their total area were studied. It was established that biological adaptation of the bats (Chiroptera), on the example of soprano pipistrelle (Pipistrellus pygmaeus), is manifested in development of biological properties of the species. The functional and protein-synthetic activity of cells, kidneys (cell volume, nucleus, cytoplasm and nuclear-cytoplasmic ratio), the number and increase in the total area of the argentophilic region of nucleolar organizers were determined by organ topography, gender and influence of anthropogenic negative environmental effects. The data obtained showed gender differences in female bats (Chiroptera) of Pipistrellus pygmaeus species living in an urban environment, having a large number in the colony, against the background of a combined anthropogenic load, under the influence of hydrocarbons, sulfur and nitrogen dioxides and suspended solids. It was found that phenotypic adaptation as an adaptation to flight triggers the main processes of biochemical cycles, the processes of endogenous intoxication and detoxification function in kidneys. In turn, it increases metabolism, which contributes to increase in the number of renal glomeruli and decrease in the cavity of renal glomerular capsule. New data characterizing nuclear-cytoplasmic ratio, number and total area of regions of nucleolar organizers in podocytes of glomeruli in kidneys of soprano pipistrelle (Pipistrellus pygmaeus), which may be a manifestation of genetic adaptation to environmental conditions, were obtained.

Sex-biased infections scale to population impacts for an emerging wildlife disease.

Demographic factors are fundamental in shaping infectious disease dynamics. Aspects of populations that create structure, like age and sex, can affect patterns of transmission, infection intensity and population outcomes. However, studies rarely link these processes from individual to population-scale effects. Moreover, the mechanisms underlying demographic differences in disease are frequently unclear. Here, we explore sex-biased infections for a multi-host fungal disease of bats, white-nose syndrome, and link disease-associated mortality between sexes, the distortion of sex ratios and the potential mechanisms underlying sex differences in infection. We collected data on host traits, infection intensity and survival of five bat species at 42 sites across seven years. We found females were more infected than males for all five species. Females also had lower apparent survival over winter and accounted for a smaller proportion of populations over time. Notably, female-biased infections were evident by early hibernation and likely driven by sex-based differences in autumn mating behaviour. Male bats were more active during autumn which likely reduced replication of the cool-growing fungus. Higher disease impacts in female bats may have cascading effects on bat populations beyond the hibernation season by limiting recruitment and increasing the risk of Allee effects.

Evaluation of antioxidant enzymes in the female genital fluid of the bat Corynorhinus mexicanus during sperm storage

Abstract Female Corynorhinus mexicanus bats store sperm for three months. One cause of the death of sperm is the action of reactive oxygen species (ROS). Three antioxidant enzymes – superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPX) – regulate the REDOX state of the environment in which gametes are stored. The aim of this study was to evaluate antioxidant enzymatic activity in female genital fluid during the period of sperm storage (October-December). The activity of the enzymes in the female bats’ genital fluid was determined by spectrophotometry. SOD activity was 20 USOD/ml/min in each month. Total GPX activity was 70 UGPX/ml/min in October, but increased in November and December to 145 UGPX/ml/min. Specific CAT activity was 2000 UK/ml/min in October, but in November it increased to 16 000 UK/ml/min, then to 32 000 UK/ml/min in December. The ROS fluorescence indices in the sperm ranged from 3000 to 8000 with no significant differences. These data show that antioxidant enzymes participate in the maintenance of sperm viability in the female reproductive tract of C. mexicanus.

Long‐term exposure to an invasive fungal pathogen decreases Eptesicus fuscus body mass with increasing latitude

AbstractInvasive pathogens threaten wildlife health and biodiversity. Physiological responses of species highly susceptible to pathogen infections following invasion are well described. However, the responses of less susceptible species (relative to highly susceptible species) are not well known. Latitudinal gradients, which can influence body condition via Bergmann's rule and/or reflect the time it takes for an introduced pathogen to spread geographically, add an additional layer for how mammalian species respond to pathogen exposure. Our goal was to understand how hosts less susceptible to pathogen infections respond to long‐term pathogen exposure across a broad latitudinal gradient. We examined changes in body mass throughout pathogen exposure time across the eastern United States (latitude ranging 30.5° N–44.8° N) in Eptesicus fuscus, a bat species classified as less susceptible to infection (relative to highly susceptible species) by the invasive fungal pathogen that causes white‐nose syndrome, Pseudogymnoascus destructans (Pd). Using 30 years of spring through fall adult capture records, we created linear mixed‐effects models for female and male bats to determine how mass or mass variation changed across the eastern United States from pre‐Pd invasion years through Pd invasion (0–1 years with Pd), epidemic (2–4 years with Pd), and established years (5+ years with Pd). By Pd establishment, all female and male bats decreased body mass with increasing latitude across a spatial threshold at 39.6° N. Differences in bat mass north and south of the spatial threshold progressively increased over Pd exposure time‐steps such that body mass was lower in northern latitudes compared to southern latitudes by Pd establishment. Results indicated that the progressive differences in E. fuscus body mass with latitude across the eastern United States are due to long‐term pathogen exposure; however, other environmental and ecological pressures may contribute to decreases in E. fuscus body mass with latitude and long‐term pathogen exposure. As pathogen introductions and emerging infectious diseases become more prevalent on the landscape, it is imperative that we understand how less susceptible species directly and indirectly respond to long‐term pathogen exposure in order to maintain population health in surviving species.

Network analysis of a northern long-eared bat (Myotis septentrionalis) maternity colony in a suburban forest patch

Abstract Many bat species are highly social, forming groups of conspecifics, particularly during the maternity season. In temperate North America, these social groups are typically comprised of closely related individuals or individuals that share some common trait (i.e. reproductive state or shared hibernacula from the previous winter). In the summer, when bats use forests for day-roosts, these social groups often demonstrate nonrandom patterns of periodically associating in common roosts and disassociating using different roosts as a ‘fission–fusion society’. As cave hibernating bat species in North America continue to decline due to the impacts of White-nose Syndrome, opportunities to describe these dynamics are becoming rare. Unfortunately, these patterns often are still poorly documented, yet understanding these behaviors is critical for species-specific habitat conservation and management. In our study, we tracked female northern long-eared bats (Myotis septentrionalis) to their day-roosts in a small, suburban forest fragment in coastal New York, USA, in the summers of 2018 and 2019. We confirmed that the bats shared roost sites and, using network analyses, analyzed social dynamics and space use. In contrast to previous research on this imperiled species in large, unfragmented core forests, we found a more dense, connected roost network that concentrated around forest patch edges. Unusual for this species, primary roosts were anthropogenic structures. Our findings suggest that northern long-eared bats can utilize small forest patches and that incorporation of specific types of anthropogenic roosts might be an effective strategy for long-term conservation in more urbanized landscapes where forest management actions to enhance day-roosting conditions are impractical and the risk of stochastic loss of roosts is high.

Evening Bats Captured in a Managed Wildlife Refuge Used Trees in a Human-Dominated Landscape as Maternity Roosts

Abstract Similar to many chiropteran species, pregnant and lactating evening bats Nycticeius humeralis form maternity colonies to bear and raise their pups. Although evening bat maternity roosts have been studied in other locations, knowledge gaps exist regarding maternity roost site selection on the Gulf Coast of Texas, United States; thus, our objective was to quantify maternity roost characteristics of evening bats in this region. We radiotracked 11 female and subadult evening bats to 9 roosts during June and July 2018 and 2019 captured in San Bernard National Wildlife Refuge (SBNWR). No transmittered bats roosted in SBNWR and instead all roosts were located 3.6–4.5 km from the same capture site, within an 81-ha residential area of a 5,496-ha city. Five of the nine roosts were located in tall, live, live oak trees Quercus virginiana and one roost was in a residential home. Colony size of bats occupying the roosts ranged from 16 to 500+ bats. All evening bats, including those on properties to which we were denied access, stayed in roosts for the full life of the transmitter (5–21 d) and no roost switching occurred. Although evening bats used SBNWR, potentially for foraging, results suggest trees in the residential area provided suitable maternity roost characteristics. A lack of roost switching may suggest a lack of available roost trees in SBNWR and residential areas or the selected roost trees were high quality. We recommend future studies increase sample sizes of evening bat roosts on the Gulf Coast of Texas, as well as assessing roost site selection of evening bats and monitoring bachelor colony and evening bat winter roost ecology.

Análise morfométrica e ecologia de poleiro de espécies de morcegos Pteropus Medius em Mansehra, Khyber Pakhtunkhwa, Paquistão

Abstract Morphometric measurement and roosting ecology of Pteropus medius were aimed to find out in Mansehra district of KP, Pakistan. Total 3149 numbers of bats were found in eight biological spots visited; Baffa Doraha, Darband, Dadar, Jallu, Hazara University, Garhi Habibullah Chattar Plain and Jabori, in total 299 numbers of different species of trees including; Morus alba, Pinus raxburghi, Eucalyptus camaldulensis, Morus nigra, Grevillea robusta, Brousonetia papyrifera,Platanus orientalis, Ailanthus altissima, Hevea brasiliensis and Populus nigra. Morphometric features were measured and found vary according to sex of the bats. The average wing span, wing`s length from tip of wing to neck, from thumb to tip of wing and the body`s length from head and claws were recorded to be 102.98 cm, 49.07cm, 28.7 cm and 22.78 cm respectively in males while 93.67 cm, 44.83cm, 24.78cm and 22.78 cm respectively in female bats. Mean circumference of the body including wings and without wing were measured as 22.78 cm and 17.29 cm in males and that of female were 20.07 cm and 16.9 cm. Average length of thumb 3.64 cm, ear`s length 3.1 cm, snout 5.62cm, eye length were 1.07 cm for both sexes and length between the feet in extended position were16.3 cm. Generally different measurement of males bodies were found to be greater than female such as mean body surface area, mass, volume and pressure were found to be 2691.79 cm2, 855.7gm,1236.4 ml and 295.77 dyne/ c m 3for male and 2576.46 cm2, 852.71gm,1207 ml and 290.2 dyne/ c m 3 respectively for female. While weight and density for both males and females bats were same with mean of 8.59 newton and 0.701 g/m3. Findings of current reports can add valued information in literature about bats, which can be used for species identification and conservation.

Adaptive transformations of the organism of the Small Bat (Pipistrellus pygmaeus) under conditions of combined negative anthropogenic factors

Chiropteran mammals have unique body anatomy features that are adapta- tions for flight. However, the histophysiological, physiological, and biochemical parameters of bats have not been studied enough, including under the influence of anthropogenic fac- tors. The article presents the results of a morphological study of the internal organs and hematological and biochemical studies of the blood of bats (using the example of the small bat), living in the Bryansk region, under conditions of technogenic and anthropogenic load. During the work, somatometric measurements of the body and the measurement of the linear parameters of the internal organs were determined. Hematological and biochemical studies of the blood of the small bat were carried out on an automatic biochemical analyzer according to generally accepted methods. Morphological and anatomical adaptation of the small bat, which ensures compliance with the structure of the body and its mode of action, is manifested in the dynamics of somatometric indicators of the body, in the plasticity of macro- and micrometric indicators of the kidneys and liver. Physiological adaptation that maintains the functional state is manifested in quantitative and qualitative reactions from the cellular elements of the blood, demonstrating higher values. It has been established that the number of erythrocytes in the blood of male and female bats is directly dependent on sex, physiological state and age.

Validation of non-invasive hormone analysis techniques to assist in the future identification of maternal roosts of ghost bats (Macroderma gigas)

The ghost bat (Macroderma gigas) is the largest microbat in Australia and occupies a large but contracting range. The ghost bat is listed as Vulnerable with a decreasing population trend by the IUCN Red List of Threatened Species. They occupy caves, disused mine adits and rock crevices as daytime roosts but distinguishing which are preferred as maternal roosts is challenging as sampling is difficult, and bats are easily disturbed while roosting. Identification of maternal roosts is a priority for conservation and management purposes, and therefore non-invasive hormone analysis was investigated as a potential tool for the future identification of the cave preferences of pregnant individuals. To validate fecal progesterone metabolite analysis techniques, fecal samples were collected from group housed female ghost bats at Perth Zoo between October and January, during the expected parturition period, over three years. Fecal samples were weighed (0.025 g), extracted with 2.5 ml of 80% methanol and analyzed for progesterone metabolite levels by enzyme-immunoassay. Significant elevations in fecal progesterone metabolite levels were detected in a subset of samples collected from co-housed females prior to parturition but not after, providing biological validation of the hormone analysis techniques. Over the three years, four pups were born with birth dates ranging from early November to late December. The mean fecal progesterone metabolite levels of non-pregnant females was significantly lower than those of pregnant females (206.5 ± 102.9 ng/g and 7003.6 ± 6078.0 ng/g respectively). These techniques can be used to monitor and evaluate the reproductive health of ghost bat populations over time and help identify factors influencing maternity roost fidelity. This data will provide valuable information for the conservation and management of the ghost bat and has the potential to be applied to other bat species.

Foliage-roosting eastern red bats select for features associated with management in a central hardwood forest

Forests provide crucial foraging and roosting habitat to many bat species, and the gradual loss of forests is among the principal threats to global bat diversity. Forests that persist in the face of land use change are those that are managed for a variety of uses, including recreation, hunting, timber production, and wildlife conservation. Thus, understanding how bats respond to management is imperative to their conservation. We used radio telemetry to study the roosting and foraging behaviors of male and female eastern red bats (Lasiurus borealis). These forest-dependent bats roost in the foliage of live trees and are declining across their range. We tracked 26 bats (7 males and 18 females; one female was tracked twice) from May to August 2017–2019 in two state forests in south-central Indiana, USA. We estimated space use with 95% kernel density estimates and used generalized linear and linear mixed models to assess resource selection and use at three levels: population-level foraging selection, individual-level foraging use, and population-level roost selection. On average, eastern red bats foraged over a relatively small area (81 ha) and traveled a maximum distance of 1404 m from their roosts. The eastern red bat population foraged near maintained openings, recent regeneration openings, roads, and ponds within the study area. Within their foraging ranges, eastern red bats spent more time foraging near roads, ponds, and ridges. Eastern red bats roosted near maintained openings, recent regeneration openings, and ponds, switching roosts every two days. Roost trees were larger than random trees and were in plots containing fewer live stems than random plots. Together, these results reveal that some of the most important landscape features for eastern red bats are linear corridors (e.g., roads or ridgetops), forest openings (e.g., maintained openings and recent regeneration openings), perennial sources of water (e.g., ponds), and large trees. Overall, eastern red bats exhibited strong selection for managed portions of the forest, suggesting they can coexist with and likely benefit from timber management. When considering habitat for eastern red bats in central hardwood forests, we recommend land managers work to maintain large tracts of mature (>90 years old) forest, interspersed with young regeneration openings and provisioned with perennial water sources (e.g., ponds).

Roost Characteristics of a Tricolored Bat Perimyotis subflavus in the Missouri Ozarks

The tricolored bat (Perimyotis subflavus) once commonly occurred throughout the eastern and central United States, but is now experiencing range-wide population declines primarily due to white-nose syndrome and forest fragmentation. Conservation efforts for this species require more information regarding summer maternity roost characteristics, especially in the Ozark Highlands of Missouri, where the species has declined precipitously. Herein we report the capture and tracking of one female tricolored bat to two summer roosts in southeastern Missouri. Tree roosts differed by their substrates, as one was within a cluster of dead leaves on a snag and the other was located under exfoliating bark; otherwise, the roosts and surrounding vegetation were similar. Both roosts were located in large (>30 cm diameter breast height) oak (Quercus spp.) trees under a dense canopy of trees with similar basal areas. While our capture success was limited over two years, details regarding tricolored bat roost ecology are imperative for the species' conservation and management.

Mutual mother-pup acoustic identification in Asian particolored bats.

In many vertebrates, vocal communication is crucial in parent-offspring interactions, and parents are often able to discriminate between the calls of their own and others' offspring. There are many reports on the unidirectional recognition of isolation calls of pups by maternal bats, but few studies on the ability of bat pups to recognize maternal acoustic signals. In this study, we investigated whether the echolocation pulses of female Asian particolored bats (Vespertilio sinensis) and isolation calls of pups differ statistically among individuals. We used two-choice playback experiments to test whether the mothers and pups of V.sinensis can recognize each other by acoustic signals. Both the echolocation pulses of mother bats and the isolation calls of pups contained sufficient individual characteristics. Playback experiments showed that mothers were able to recognize isolation calls of pups, and most pups greater than 12 days old were able to distinguish echolocation pulses of their own mother from those of other mothers. This is the first use of two-choice acoustic signal playback experiments to confirm that pups can recognize their mothers by echolocation calls. The results provide behavioral evidence for bidirectional recognition of acoustic signals between mothers and infants in frequency-modulated type bats.

Roost fidelity partially explains maternity roosting association patterns in Myotis lucifugus

Resources that draw individuals to a specific location may result in the formation of groups and development of individual social preferences. Simultaneously considering both ecological and social factors can therefore reveal underlying mechanisms of group formation and organization. Females of some temperate bat species roost in groups during the spring and summer months within which they give birth to and nurse their pups. Females switch roosts frequently, but the factors that influence roost switching remain poorly understood. To characterize the structure of a bat maternity group and gather evidence for the role of social preference in shaping this structure, we used roost co-occurrence data from little brown myotis, Myotis lucifugus , implanted with passive integrated transponder tags and roost boxes monitored with passive readers in Salmonier Nature Park, Newfoundland, Canada. By developing informed null models, we more directly investigate hypotheses that may explain why bats roost together. Although our results suggest that association patterns of maternity groups can largely be explained by similar interindividual patterns in bats' roosting frequencies within a given roost box (roost fidelity), other factors are likely to contribute to the observed structure. We thus provide support for the potential influence of roost and social preferences in shaping maternity group structure. • Female bats frequently switch roosts, changing who they roost with each day. • Some bats did not roost together at frequencies expected by chance. • Other bats occasionally roosted together more than expected by chance. • Social preferences may be important in influencing roosting decisions.

Sexual segregation occurs in bats within fragmented remnant woodlands in an agricultural landscape.

Species‐specific responses to landscape configuration and landscape composition have been studied extensively. However, little work has been done to compare intraspecific differences in habitat preferences. Bats have potential as good bioindicator taxa in woodland habitats. Therefore, studying sex differences in responses to woodland and the wider landscape can allow us to gain insight into the relative importance of these habitats for both bats and other taxa. In this study, we aimed to test the predictions that (i) habitat type and connectivity will influence the probability of recording female bats in woodlands and (ii) sex differences in response to habitat type and connectivity will be species‐specific. Bat capture data was collected in 206 woodlands over 3 years in England. The probability of detecting females relative to males was modeled in response to a range of woodland characteristics and landscape metrics for six bat species. We recorded sex differences in responses to landscape features in three species. We found a higher probability of capturing female Myotis nattereri in woodlands that were surrounded by a higher proportion of improved grasslands, whereas female Myotis mystacinus were less likely to be recorded in woodlands surrounded by semi‐natural vegetation. Female Plecotus auritus were more likely to be recorded in isolated woodlands with less connectivity to other woodlands and where agriculture dominated the surrounding landscape. Our findings indicate that sexual segregation occurs across several UK bat species in response to landscape connectivity and composition. Sexual segregation in response to landscape characteristics in bats should therefore be an important consideration in the management of fragmented agricultural landscapes.

Physiological and Ecological Correlates of the Cellular and Humoral Innate Immune Responses in an Insular Desert Bat: The Fish-Eating Myotis (Myotis vivesi)

The immune response is affected by aridity, but it has been rarely examined in desert-dwelling bats. For two consecutive years, we examined the seasonal variation in the innate immune response of an insular desert bat, the fish-eating myotis (Myotis vivesi), in relation to its reproductive activity and ectoparasite load. We evaluated the reproductive activity based on external morphological traits and testosterone levels in the plasma for males and progesterone and estradiol for females. We injected phytohemagglutinin (PHA) into the footpads of the bats to estimate the innate cellular response, and we measured the bacterial killing ability (BKA) of the blood plasma to determine the innate humoral response. Both the external morphological traits and hormone levels indicate that the females were pregnant in spring and lactating in summer, and that the males were reproductively active in autumn, when mating probably occurred. The swelling response of the female and male bats was lower in spring. The BKA in the males did not vary seasonally; the BKA in the females varied seasonally but only in the first year of the study, with lower values in spring and summer. The BKA in spring was lower in the first year of the study, when the females appeared to be in early pregnancy, compared to the second year, when the females were in advanced pregnancy. The swelling increased as the body mass and body conditions of the males increased, but the BKA was not correlated with body mass or body condition in either sex. Ectoparasite abundance and prevalence did not vary among seasons. Ectoparasite abundance was not correlated with the PHA response in both sexes; it was not correlated with the BKA in females, but it was inversely correlated in males. Of the three hormones measured, only estradiol was correlated with the immune response: females with higher estradiol levels had a higher PHA response and BKA. Our findings indicate that the cellular and humoral innate immune responses of the fish-eating myotis varied throughout the year, following the seasonal reproductive pattern of the species. Our evaluation of the proximal factors affecting the expression of the immune response points to the potential immunoregulatory role of sex hormones and body mass.

Flexible energy-saving strategies in female temperate-zone bats

Torpor is characterized by an extreme reduction in metabolism and a common energy-saving strategy of heterothermic animals. Torpor is often associated with cold temperatures, but in the last decades, more diverse and flexible forms of torpor have been described. For example, tropical bat species maintain a low metabolism and heart rate at high ambient and body temperatures. We investigated whether bats (Nyctalus noctula) from the cooler temperate European regions also show this form of torpor with metabolic inhibition at high body temperatures, and whether this would be as pronounced in reproductive as in non-reproductive bats. We simultaneously measured metabolic rate, heart rate, and skin temperature in non-reproductive and pregnant females at a range of ambient temperatures. We found that they can decouple metabolic rate and heart rate from body temperature: they maintained an extremely low metabolism and heart rate when exposed to ambient temperatures changing from 0 to 32.5 °C, irrespective of reproductive status. When we simulated natural temperature conditions, all non-reproductive bats used torpor throughout the experiment. Pregnant bats used variable strategies from torpor, to maintaining normothermy, or a combination of both. Even a short torpor bout during the day saved up to 33% of the bats' total energy expenditure. Especially at higher temperatures, heart rate was a much better predictor of metabolic rate than skin temperature. We suggest that the capability to flexibly save energy across a range of ambient temperatures within and between reproductive states may be an important ability of these bats and possibly other temperate-zone heterotherms.

Hibernating bats may use protein stores for water balance

All hibernating bats need to eat enormous amounts of food during autumn to build up a substantial fat store for hibernation. These large fat stores supply the immense amount of energy needed to survive without access to food and water. However, little is known about how the breakdown of proteins from muscles and organs contribute to the hibernating animal's energy stores and possibly their water budget. Liam McGuire from Texas Tech University, USA (now at the University of Waterloo, Canada), and colleagues from Montanan State University, Texas Tech University and the Wildlife Conservation Society, all in the USA, set out to investigate how proteins from the muscles and organs of two species of bats are used for energy and water during hibernation.In October 2016, before the bats entered hibernation, the team observed 184 cave myotis (Myotis velifer) in a cave in Oklahoma, taking measurements of the animals’ forearm length (a measurement of body size), determining their sex and using a mobile laboratory to measure the amount of fat, muscle and organ masses. Next, the team collected the same measurements from 65 Townsend's big-eared bats (Corynorhinus townsendii) at two caves in eastern Nevada during both the fall and winters of 2017–2019 to track changes in the fat, muscle and organ masses as the animals hibernated. Then, the team calculated the amount of energy and water generated by the Townsends’ big-eared bats from the decreases in fat, muscle and organ mass.McGuire and colleagues found that prior to entering hibernation, muscle and organ masses in the cave myotis was ∼25–38% of the animals’ total body mass. The team suspect that during this period, the bats build up their digestive organs to allow them to binge and build up their fat reserves in addition to bulking up their muscles to carry the large fat store. However, larger muscles and organs also provide bats with access to protein throughout hibernation. In addition, the males had proportionally larger muscles and organs, whereas the females had more body fat, which the researchers suggested may be due to differences in the animals’ reproduction strategies. Females need to conserve energy reserves throughout hibernation in preparation for possible pregnancies following hibernation. With their larger protein stores, the males have greater flexibility when arousing from hibernation to burn through organs and muscle to fuel their energy and water requirements, as protein breakdown produces more water compared to fat. But how did the hibernating big-eared bat reserves hold during their long hibernations?The males consumed approximately twice the amount of muscle and organ tissue than the females, accounting for 35% of the males’ total body mass loss and contributing 7% of the energy they used during hibernation. The females, however, had more body fat and were able to generate more energy as fat produces larger amounts of energy relative to protein. The researchers calculated how much water the animals generate as they both broke down muscle and organs and discovered that, after they subtracted the additional water that the animals lost excreting the toxic waste products generated by consuming protein, the female bats benefited by retaining four times more of the water they generated than the males. The team argues that bats could potentially use protein breakdown for hydration during hibernation.McGuire and colleagues have successfully shown that bats build up their muscles and organs prior to hibernation, which could be used as a minor source of energy but could also play a major role in the production of water. Relatively little is known about how hibernating bats using protein as a source of water, but this new study opens the flood gates to new avenues in bat hibernation research.