Nycticeius Humeralis Research Articles

Inter- and intraspecific variability of total mercury concentrations in bats of Texas (USA)

Exposure to mercury (Hg) may cause deleterious health effects in wildlife, including bats. Texas produces more Hg pollution than any other state in the United States, yet only one study has examined Hg accumulation in bats. This study measured the concentration of total Hg (THg) in fur (n = 411) collected from ten bat species across 32 sites in eastern and central Texas, USA. Fur THg concentrations were compared among species, and when samples sizes were large enough, between sex and life stage within a species, and the proximity to coal-fired power plants. For all sites combined and species with a sample size ≥8, mean THg concentrations (μg/g dry weight) were greatest in tri-colored bats (Perimyotis subflavus; 6.04), followed by evening bats (Nycticeius humeralis; 5.89), cave myotis (Myotis velifer; 2.11), northern yellow bats (Lasiurus intermedius; 1.85), Brazilian free-tailed bats (Tadarida brasiliensis; 1.03), and red bats (Lasiurus borealis/blossevillii; 0.974), and lowest in hoary bats (Lasiurus cinereus; 0.809). Within a species, fur THg concentrations did not significantly vary between sex for the five examined species (red bat, northern yellow bat, cave myotis, evening bat, Brazilian free-tailed bat) and only between life stage in evening bats. Site variations in fur THg concentrations were observed for evening bats, tri-colored bats, and Brazilian free-tailed bats. Evening bats sampled closer to point sources of Hg pollution had greater fur THg concentrations than individuals sampled further away. Sixteen percent of evening bats and 8.7% of tri-colored bats had a fur THg concentration exceeding the 10 μg/g toxicity threshold level, suggesting that THg exposure may pose a risk to the health of bats in Texas, particularly those residing in east Texas and on the upper Gulf coast. The results of this study can be incorporated into future management and recovery plans for bats in Texas.

Sample Size and Geometric Morphometrics Methodology Impact the Evaluation of Morphological Variation.

Geometric morphometrics has had a profound impact on our understanding of morphological evolution. However, factors such as sample size and the views and elements selected for two-dimensional geometric morphometric (2DGM) analyses, which are often dictated by specimen availability and time rather than study design, may affect the outcomes of those analyses. Leveraging large intraspecific sample sizes (n>70) for two bat species, Lasiurus borealis and Nycticeius humeralis, we evaluate the impact of sample size on calculations of mean shape, shape variance, and centroid size. Additionally, we assessed the concordance of multiple skull 2D views with one another and characterized morphological variation in skull shape in L. borealis and N. humeralis, as well as a closely related species, Lasiurus seminolus. Given that L. seminolus is a morphologically cryptic species with L. borealis, we assessed whether differences in skull shape and in 2DGM approach would allow species discrimination. We found that reducing sample size impacted mean shape and increased shape variance, that shape differences were not consistent across views or skull elements, and that trends shown by the views and elements were not all strongly associated with one another. Further, we found that L. borealis and L. seminolus were statistically different in shape using 2DGM in all views and elements. These results underscore the importance of selecting appropriate sample sizes, 2D views, and elements based on the hypothesis being tested. While there is likely not a generalizable sample size or 2D view that can be employed given the wide variety of research questions and systems evaluated using 2DGM, a generalizable solution to issues with 2DGM presented here is to run preliminary analyses using multiple views, elements, and sample sizes, thus ensuring robust conclusions.

Experimental trials of species-specific bat flight responses to an ultrasonic deterrent.

Unintended consequences of increasing wind energy production include bat mortalities from wind turbine blade strikes. Ultrasonic deterrents (UDs) have been developed to reduce bat mortalities at wind turbines. Our goal was to experimentally assess the species-specific effectiveness of three emission treatments from the UD developed by NRG Systems. We conducted trials in a flight cage measuring approximately 60 m × 10 m × 4.4 m (length × width × height) from July 2020 to May 2021 in San Marcos, Texas, USA. A single UD was placed at either end of the flight cage, and we randomly selected one for each night of field trials. Trials focused on a red bat species group (Lasiurus borealis and Lasiurus blossevillii; n = 46) and four species: cave myotis (Myotis velifer; n = 57), Brazilian free-tailed bats (Tadarida brasiliensis; n = 73), evening bats (Nycteceius humeralis; n = 53), and tricolored bats (Perimyotis subflavus; n = 17). The trials occurred during three treatment emissions: low (emissions from subarrays at 20, 26, and 32 kHz), high (emissions from subarrays at 38, 44, and 50 kHz), and combined (all six emission frequencies). We placed one wild-captured bat into the flight cage for each trial, which consisted of an acclimation period, a control period with the UD powered off, and the three emission treatments (order randomly selected), each interspersed with a control period. We tracked bat flight using four thermal cameras placed outside the flight cage. We quantified the effectiveness of each treatment by comparing the distances each bat flew from the UD during each treatment vs. the control period using quantile regression. Additionally, we conducted an exploratory analysis of differences between sex and season and sex within season using analysis of variance. Broadly, UDs were effective at altering the bats' flight paths as they flew farther from the UD during treatments than during controls; however, results varied by species, sex, season, and sex within season. For the red bat group, bats flew farther from the UD during all treatments than during the control period at all percentiles (p < 0.001), and treatments were comparable in effectiveness. For cave myotis, all percentile distances were farther from the UD during each of the treatments than during the control, except the 90th percentile distance during high, and low was most effective. For evening bats and Brazilian free-tailed bats, results were inconsistent, but high and low were most effective, respectively. For tricolored bats, combined and low were significant at the 10th-75th percentiles, high was significant at all percentiles, and combined was most effective. Results suggest UDs may be an effective means of reducing bat mortalities due to wind turbine blade strikes. We recommend that continued research on UDs focus on low emission treatments, which have decreased sound attenuation and demonstrated effectiveness across the bat species evaluated in this study.

The Geographical Differences in the Bird Prey of the Great Evening Bat (Ia io)

Geographic variation in diet can indicate if species have unique ecological roles or feeding strategies in different environments. Bats have a unique nocturnal ecological niche and a diverse diet, making them an ideal model for studying changes in feeding. Some bats have adapted to reduced food resources caused by environmental changes and human disturbances by expanding their dietary ecological niche. As one of the typical species whose dietary niche has expanded from invertebrates (insects) to vertebrates (birds), the feeding habits of the great evening bat (Ia io) have attracted much attention from researchers. Unfortunately, little is known about how the diet of Ia io varies in different regions. Therefore, in this study, the diversity and composition of the bird prey of the great evening bat from two populations were examined using cytochrome C oxidase subunit I (COI) amplicon sequencing. The results showed that the great evening bat in both populations preyed on a variety of passerine birds, with the Phylloscopidae being the dominant family. Although most birds preyed upon by these two populations are the same, there are significant differences in predation on Cettiidae between the two populations. Both populations prey on migratory birds more than resident birds. Both populations of bats can prey on finch birds weighing more than 15 g, but they preyed on more birds weighing less than 10 g. The results of this study provide an important addition to the study of changes in bat diets under the conditions of expanding dietary ecological niches.

Selection of Maternity Roosts by Evening Bats (Nycticeius humeralis) in a Riparian Forest at the Northern Edge of Their Range

Selection of Maternity Roosts by Evening Bats (Nycticeius humeralis) in a Riparian Forest at the Northern Edge of Their Range

Westward expansion of the Evening Bat (Nycticeius humeralis) into Dawson and Lincoln counties of central Nebraska

The Evening Bat (Nycticeius humeralis) is a small, migratory species of temperate woodlands in the eastern United States. Along its western distributional edge in the Great Plains, this species resides in wooded riverine corridors. In recent decades, the distribution of Evening Bats has expanded westward throughout the Great Plains. Herein, we report on two county records that further document the distributional expansion of Evening Bats into central Nebraska. In 2019 and 2022, Evening Bats were collected in Lincoln and Dawson counties, respectively, in woodlands adjacent to the Platte River. Increases in wooded habitats along prairie waterways likely has resulted in their westward movements in the Great Plains. With the continued westward expansion, this species should be looked for farther west beyond known distributional limits along prairie waterways throughout the Great Plains.

Linking changes in individual specialization and population niche of space use across seasons in the great evening bat (Ia io)

BackgroundThe niche breadth of an animal population comprises both within-individual and between-individual variation (individual specialization). Both components can be used to explain changes in population niche breadth, and this has been extensively investigated in dietary niche dimension studies. However, little is known about how changes in food resources or environmental factors across seasons affect changes in individual and population space use within the same population.MethodsIn this study, we used micro-GPS loggers to capture the space use of individuals and of a population of the great evening bat (Ia io) in summer and autumn. We used I. io as a model to investigate how individual spatial niche breadth and spatial individual specialization affect changes in population niche breadth (home range and core area sizes) across seasons. Additionally, we explored the drivers of individual spatial specialization.ResultsWe found that the population home range and the core area of I. io did not increase in autumn when insect resources were reduced. Moreover, I. io showed different specialization strategies in the two seasons: higher spatial individual specialization in summer and lower individual specialization but broader individual niche breadth in autumn. This trade-off may maintain the dynamic stability of the population spatial niche breadth across seasons and facilitate the population response to changes in food resources and environmental factors.ConclusionsLike diet, spatial niche breadth of a population also may be determined by a combination of individual niche breadth and individual specialization. Our work provides new insights into the evolution of niche breadth from the spatial dimension.

Preliminary Characterization of Facial and Oral Microbiomes of Three Bat Species Commonly Occurring in Northwest Kansas

Various bat species are at risk due to White-Nose Syndrome, a disease rapidly spreading throughout the United States. Metagenomic research on the microbiome of bats’ mouths and noses may provide helpful information to characterize how bats’ microbiomes interact with White-Nose Syndrome so that this disease may be mitigated. However, minimal research has been conducted in characterizing bats’ oral and facial microbial populations. To address this issue, we analyzed the oral and facial microbiomes of bat species commonly occurring in Northwestern Kansas. Oral and facial swabs were taken from Tricolor, Big Brown, and Evening bat (n=1 per species). Bacterial DNA was isolated from swabs, and the V3/V4 region of the 16s DNA was amplified using polymerase chain reactions (PCR). The PCR products were purified and sequenced. Sequencing data was then analyzed using Galaxy bioinformatics software. Results showed that the majority of bacteria present in facial swabs was Alteromonas, reflecting the high mineral content in the water source that bats use. Oral bacterial population profiles of Tricolor and Big Brown bats were more diverse than their respective facial samples. In contrast, oral and facial swabs from the Evening bat had similar bacterial population profiles. Our preliminary study showed that the oral samples appeared more diverse in bacterial populations than in facial. Therefore, our future studies should investigate the difference between oral and facial bacteria population profiles in more detail by investigating a larger sample and increasing bat species diversity. Further research should also include the seasonal effects on bacterial populations. The College of St. Scholastica Summer Undergraduate Research Fellowship This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Multi-scale temporal characters mining for bird activities based on historical avian radar system datasets

AbstractAvian radar systems are effective for wide-area bird detection and tracking, but application significances need further exploration. Existing radar data mining methods provide long-term functionalities, but they are problematic for bird activity modelling especially in temporal domain. This paper complements this insufficiency by introducing a temporal bird activity extraction and interpretation method. The bird behaviour is quantified as the activity degree which integrates intensity and uncertainty characters with an entropy weighing algorithm. The method is applicable in multiple temporal scales. Historical radar dataset from a system deployed in an airport is adopted for verification. Temporal characters demonstrate good consistency with understandings from local observers and ornithologists. Daily commuting and roosting characters of local birds are well reflected, evening bat activities are also extracted. Night migration activities are demonstrated clearly. Results indicate the proposed method is effective in temporal bird activity modelling and interpretation. Its integration with bird strike risk models might be more useful for airport safety management with wildlife interference.

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.

A Survey of Bats at Lilley Cornett Woods Appalachian Ecological Research Station, Letcher County, Kentucky, before the Arrival of White-nosed Syndrome

Bat species associated with the Lilley Cornett Woods Appalachian Ecological Research Station (LCW) were documented over two field seasons. Mist netting was conducted during July 2009 [13 net nights], whereas acoustical monitoring was conducted from May–August 2010, with sampling occurring continuously for 85 nights. A total of 26 individuals, representing 5 species were captured: little brown bat (Myotis lucifugus; n = 11), tricolored bat (Perimyotis subflavus; n = 6), northern long-eared bat (Myotis septentrionalis; n = 6), big brown bat (Eptesicus fuscus; n = 2), hoary bat (Lasiurus cinereus; n = 1). There were 34,425 identified echolocation passes identifying 9 different bat species, i.e., tricolored bat, little brown bat, northern long-eared bat, big brown bat, Indiana bat (Myotis sodalis), gray bat (Myotis grisescens), eastern red bat (Lasiurus borealis), eastern small-footed bat (Myotis leibii), and evening bat (Nycticeius humeralis)]. Multiple species detected at LCW have been classified by the U.S. Fish and Wildlife Service (USFWS) as endangered (Indiana bat and gray bat) and threatened (northern long-eared bat). Since it was first detected, WNS has spread rapidly across North America and is associated with host mortality of >90%. We strongly recommend the Chiropteran community at LCW be resurveyed to assess the impacts of WNS, and that a passive acoustical monitoring program be developed and integrated into the area's long-term management plan.

The influence of forest management practices on seasonal bat species occurrence and activity at the Kisatchie National Forest in Louisiana, USA

In the southeastern United States, where forests are the primary land cover type, understanding how forest stand characteristics and forest management practices influence bat distributions is critical for bat conservation and management. We deployed passive acoustic monitors to record bat calls at sites representing six forest types at the Kisatchie National Forest in central Louisiana during two winter (January–February 2020 and December 2020–February 2021) and two summer (June–August 2020 and 2021) periods. We also collected environmental data at the landscape and local scales to help explain patterns in bat species occurrence. We detected big brown bats (Eptesicus fuscus), eastern red/Seminole bats (Lasiurus borealis/L. seminolus), Myotis species, tricolored bats (Perimyotis subflavus), Mexican free-tailed bats (Tadarida brasiliensis), and hoary bats (Aeorestes cinereus) during both periods, and additionally detected evening bats (Nycticeius humeralis) during the summer. We observed seasonal differences in habitat use, and found that three bat species were more active during the summer in pine forests with group selection harvest, pine forests managed for red-cockaded woodpeckers (Leuconotopicus borealis), and pine forests that were clearcut within five years of our study when compared to unmanaged pine forests, thinned pine forests, and bottomland hardwood forests. Contrary to other studies, we found that the predicted probability of occupancy decreased with increasing proximity to riparian areas for four bat species, which could reflect the complex understory vegetation conditions that we observed along the riparian corridors in our study area. Our research identified forest characteristics and management practices that promote bat species diversity and activity in central Louisiana and demonstrated that pine forests with open understories and small openings in the canopy provide important foraging habitat for bats that occur in our study area and possibly other regions in the southeast.

Consumption of endemic arbovirus mosquito vectors by bats in the southeastern United States.

Mosquitoes affect human health and well-being globally through their roles as disease-causing pathogen vectors. Utilizing genetic techniques, we conducted a large-scale dietary study of three bat species common to the southeastern U.S.A., Lasiurus seminolus (Seminole bat), Nycticeius humeralis (evening bat), and Myotis austroriparius (southeastern myotis). Through next-generation sequencing of a 180 bp portion of cytochrome oxidase subunit I (COI) of mitochondrial DNA from 180 bat guano samples, we documented consumption of 17 species of mosquitoes by bats, including six endemic arbovirus vectors. Culex quinquefasciatus, Culex coronator, Culiseta melanura, Culex salinarius, Culex erraticus, and Coquillettidia perturbans were consumed by 51.3%, 43.7%, 27.2%, 22.8%, 18.0%, and 12.7% of bats sampled, respectively. Consumption of two of these mosquito species was explained by spatial variables reflecting the prevalence of mosquito larval habitat, five were explained by bat traits (bat mass, bat species), and two were explained by these factors plus temporal variables (maximum daily temperature, time since sunset, date), making it challenging to offer specific guidance on how best to promote bats as a means of reducing arbovirus vector species. Our results show that common bat species of the southeastern U.S.A. consume endemic, but not exotic, arbovirus mosquito vectors. Future studies are needed to understand the impact of bat consumption on mosquito numbers and public health.

Changes in the Forest Bat Community After Arrival of White-Nose Syndrome in the Ouachita Mountains of Arkansas

Populations of some cave-hibernating bats have undergone declines in recent years due to an introduced fungus (Pseudogymnoascus destructans) that causes the disease white-nose syndrome (WNS), which is often fatal to bats during hibernation. Unprecedented declines in cave-hibernating species have the potential to change community composition via numerous mechanisms, including competitive release. We trapped bats for 6 years in the Ouachita Mountains of Arkansas prior to the arrival of WNS in the region and compared capture rates of 7 species to capture rates collected in 2020–2021 after WNS establishment. We found a 98% decline in Myotis septentrionalis (Northern Long-eared Bat) and a 77% decline in Perimyotis subflavus (Tricolored Bat) after WNS became prevalent. Nycticeius humeralis (Evening Bat) captures increased by 220% after WNS. Capture rates of Eptesicus fuscus (Big Brown Bat) increased by 100%, but this increase was not significant. We also found no significant differences in captures rates for Lasiurus borealis (Eastern Red Bat), Lasiurus seminolus (Seminole Bat), and Lasiurus cinereus (Hoary Bat) after the arrival of WNS. Our results indicate that the forest bat community of the Ouachita Mountains has been altered since the arrival of WNS in 2012, but it is unknown if these changes are permanent or if species will decline further or recover via adaptive or genetic changes in their populations in the future.

Habitat Associations of Overwintering Bats in Managed Pine Forest Landscapes

Research Highlights: Seasonal variation in environmental conditions coinciding with reproductive and energetic demands might result in seasonal differences in species-specific habitat use. We studied a winter assemblage of insectivorous bats and found that species acted as habitat generalists during winter compared to expectations based on the summer active season. Background and Objectives: In temperate regions, seasonal fluctuations in resource availability might restructure local bat assemblages. Initially perceived to only hibernate or migrate to avoid adverse winter conditions, temperate insectivorous bats appear to also employ intermediate overwintering strategies, as a growing body of literature suggests that winter activity is quite prevalent and even common in some lower latitude areas. However, to date, most studies have exclusively assessed habitat associations during summer. Because habitat use during summer is strongly influenced by reproduction, we hypothesized that habitat associations might differ during the non-reproductive winter period. We used acoustic monitoring to assess the habitat associations of bats across a managed pine landscape in the southeastern United States. Materials and Methods: During the winters of 2018 and 2019, we deployed acoustic detectors at 72 unique locations to monitor bat activity and characterized vegetation conditions at two scales (microhabitat and landscape). We used linear mixed models to characterize species-specific activity patterns associated with different vegetation conditions. Results: We found little evidence of different activity patterns during winter. The activity of three species (hoary bat: Lasiurus cinereus; southeastern myotis: Myotis austroriparius; and tricolored bat: Perimyotis subflavus) was not related to vegetation variables and only modest relationships were evident for four other species/groups (big brown bat: Eptesicus fuscus; eastern red bat: L. borealis; Seminole bat: L. seminolus; evening bat: Nycticeius humeralis; and Brazilian free-tailed bat: Tadarida brasiliensis). Conclusions: During winter, the bats in our study were active across the landscape in various cover types, suggesting that they do not exhibit the same habitat associations as in summer. Therefore, seasonal differences in distributions and habitat associations of bat populations need to be considered so that effective management strategies can be devised that help conserve bats year round.

Evening Bats (Nycticeius humeralis) Use Bird Nest Boxes as Day Roosts in Northeastern Arkansas

Forest bats, including evening bats (Nycticeius humeralis), sometimes roost in manmade structures, such as barns and bridges, but here we report the first observations of evening bats using bird nest boxes for roosting on multiple occasions between 2012 and 2019, a few kilometers north of Jonesboro, Arkansas. Most encounters were in August, when the nesting season is almost finished. We discuss timing and factors that may explain use of bird nest boxes for roosting by bats.

Four Years Continuous Monitoring Reveals Different Effects of Urban Constructed Wetlands on Bats

Proactive artificial wetland constructions have been implemented to mitigate the loss of wetlands and their ecosystem services. As wetlands are habitats for bats, short-term (one or two years) studies find that constructed wetlands can immediately increase local bat activity and diversity. However, it is not clear how constructed wetlands affect bats through time while the wetlands are aging. We collected four years of continuous bat acoustic monitoring data at two constructed wetlands in an urban park in Greensboro, NC, USA. We examined bat activity and community composition patterns at these wetlands and compared them with reference sites in the city. With four years of data, we found that the effects of constructed wetlands were both habitat- and species-specific. The wetland in forests significantly increased bat activity, while the wetland in the open grass altered bat community composition. Specifically, in terms of species, we found that over time, constructed wetlands no longer attracted more big brown, silver-haired, or evening bats than control sites while the wetlands aged, highlighting the need to study broadly how each bat species uses natural and artificial wetlands. We emphasize the importance of long-term monitoring and the periodical evaluation of wildlife conservation actions.

Seasonal variation in home range size of evening bats (Nycticeius humeralis) in an urban environment

Abstract Despite the negative impacts of urbanization on bats, green spaces in urban environments, such as parks, cemeteries, and golf courses, have the potential to provide resources necessary for these animals. Water resources in these areas include natural or semi-natural ponds, streams, and drainage ditches. Such water resources, however, are frequently ephemeral when subject to prolonged periods of high temperatures and low precipitation. We hypothesized that home ranges of evening bats (Nycticeius humeralis) would increase in size or shift from urban green spaces into surrounding neighborhoods to access alternative resources, such as residential swimming pools, when water resources in green spaces are scarce. To explore whether seasonal variations in bat home ranges occurred, we radio-tracked resident evening bats in a local park system during their summer activity period 2017–2019 in Fort Worth, Texas, USA. We used Local Convex Hulls created by associating point locations with their nearest neighbor to estimate home range size, location, and the percentage area that fell within the surrounding neighborhood. We compared these variables to temperature and precipitation using various regression models. We successfully tracked 30 bats over the 3-year period and found a positive correlation between home range size and temperature. Home range sizes increased 6-fold when temperatures exceeded 30°C. Our study indicates the importance of urban neighborhoods surrounding green spaces in providing alternative resources, such as water, for bats. If managed appropriately, these urban areas have the potential to act as oases for bat populations.

Seasonal Dietary Shifts Alter the Gut Microbiota of Avivorous Bats: Implication for Adaptation to Energy Harvest and Nutritional Utilization

ABSTRACTPlasticity in the microbial community composition and function can permit the host to adapt to ecological, environmental, and physiological changes. Much of the information on the gut microbiota-host relationship to date derives from studies of laboratory model organisms, while little is known concerning wild animals and their ecological relevance to gut microbes. It is also unclear how microbial community composition and activity adapt to changes in diet and energy, nutritional requirements, and utilization induced by dietary expansion from invertebrates to vertebrates. The great evening bat (Ia io) is both an insectivore and an avivore (that is, a bird-eater), and thus provides an opportunity to investigate the diet-host-microbiota-physiology relationship. Here, we investigated this relationship by using 16S rRNA amplicon sequencing and functional prediction in adult males of I. io. We found that gut microbial diversity was similar, while microbial community structures were significantly different between insectivorous and avivorous diets. Moreover, increases in the relative abundance of Firmicutes and the Firmicutes-to-Bacteroidetes ratio, changes in carbohydrate and nucleotide metabolism, and a decrease in Pseudomonas were associated with higher energy demands for hunting birds and with fat storage for entering hibernation and migration. These findings demonstrated that seasonal dietary shifts drive a significant change in the composition and function of gut microbiomes, thereby facilitating adaptation to the challenging avian dietary niche in bats. These results suggest that the gut microbial communities can constantly respond to alterations in diets, potentially facilitating the diversity of wild animal dietary niches, and enhance our understanding of the diet-host-microbiota-physiology relationship.IMPORTANCE The coevolution between the host and its gut microbes can promote an animal’s adaptation to its specific ecological niche and changes in energy and nutritional requirements. This study focused on an avivorous bat, the great evening bat (Ia io), to investigate how seasonal dietary shifts affect the gut microbial composition and function, thereby facilitating adaptation to an avian diet. We found that seasonal dietary shifts driving a significant change in the composition and function of gut microbiomes in I. io were associated with higher energy demands for hunting birds and fat storage for entering hibernation and migration. Our study provides novel insight into the role of gut bacteria in generating ecological diversity and flexibility in wild mammals. The results are valuable for clarifying the complicated host-microbiota-physiology relationship in a dietary niche expansion context.

Who's for dinner? Bird prey diversity and choice in the great evening bat, Ia io.

The mysterious predator–prey interaction between bats and nocturnally migrating birds is a very rare and incredible process in natural ecosystems. So far only three avivorous bat species, including two noctule bats (Nyctalus lasiopterus and Nyctalus aviator) and the great evening bat (Ia io), are known to regularly prey on songbirds during nocturnal avian migration. The information related to the diversity and the characteristics of the birds as prey and the hunting strategy in both species of noctule bats are already clear. However, the diversity of bird prey in the diet of I. io as confirmed by molecular identification remains unknown. Moreover, like hunting insects, it remains unclear whether the avivorous bats opportunistically prey on birds. Here, we used DNA metabarcoding to investigate the bird prey composition, diversity, and choice in diets of I. io. We found I. io consumed 22 species of seven families from Passeriformes with a body mass of 6–19 g, and preferentially selected small‐sized passerine birds for optimizing the benefit/risk trade‐off. Moreover, most of the species preyed upon were migratory birds, while four species were local resident birds, indicating that I. io may adopt both aerial‐hawking and gleaning strategies on songbirds as do the other two noctules. Further, I. io body mass did not influence in prey choice and predation richness on birds, suggesting I. io is an opportunistic avivorous predator. This study provides novel insights into the avian dietary ecology of I. io and completes the analysis of predator/prey interaction between three avivorous bats and nocturnally migrating birds. Our results also indicate bat predation on birds which occurs as an act of ecological opportunity may subject bats to intense natural selection pressure, causing them access to the new diet‐defined adaptive zones.