Cave Roosts Research Articles

BatCount: A software program to count moving animals.

One of the biggest challenges with species conservation is collecting accurate and efficient information on population sizes, especially from species that are difficult to count. Bats worldwide are declining due to disease, habitat destruction, and climate change, and many species lack reliable population information to guide management decisions. Current approaches for estimating population sizes of bats in densely occupied colonies are time-intensive, may negatively impact the population due to disturbance, and/or have low accuracy. Research-based video tracking options are rarely used by conservation or management agencies for animal counting due to the perceived training and elevated operating costs. In this paper, we present BatCount, a free software program created in direct consultation with end-users designed to automatically count bats emerging from cave roosts (historical populations 20,000-250,000) with a streamlined and user-friendly interface. We report on the software package and provide performance metrics for different recording habitat conditions. Our analysis demonstrates that BatCount is an efficient and reliable option for counting bats in flight, with performance hundreds of times faster than manual counting, and has important implications for range- and species-wide population monitoring. Furthermore, this software can be extended to count any organisms moving across a camera including birds, mammals, fish or insects.

Out of the bat lab and into the field: Sensorimotor strategies of bats at high-speed flight

The experiments performed by James Simmons helped pave the way for our understanding of bat biosonar processing and “what it’s like to be a bat.” By conducting experiments with trained bats, he discovered key information on how bats use temporal and spectral cues in their echoes to perceive their environment. After spending my postdoc with Dr. Simmons in his lab, he encouraged me to venture to the field to explore the sonar behavior of bats in their natural environment. This talk will summarize my recent work exploring sensorimotor behavior of free-tailed bats when returning to their cave roost at speeds exceeding 60 km/h. By combining acoustic recordings with multiple-camera recordings, we reconstructed the 3D path of bats in flight both during and in-between pulse emission. From these data we examined how acoustic behavior changed depending on altitude and velocity, and whether changes in flight trajectory or kinematics coincided with the reception of echoes. Our results demonstrate that when echolocating at fast flight speeds, bats use a predictable, open-loop sensing strategy to navigate their environment. This may be advantageous for bats flying at fast speeds and experiencing high g forces, as the physiological consequences of closed-loop sensing may be too demanding.

Modeling migration and movement of gray bats

AbstractManaging landscapes for migratory species is challenging when migratory movement patterns are unknown. Researchers have collected sufficient data to understand summer and winter habitat use for federally listed bats, but movement between these habitats in spring and fall has not been studied extensively. In addition, movement within summer habitat is less well understood than the roosting requirements. To initiate a preliminary understanding of movement patterns of gray bats (Myotis grisescens), we gathered all occurrence and band recovery data available within the range of the species to model movement. By weighting the pathways using the population of winter and summer locations (i.e., cave roosts), we created a heat map demonstrating the likelihood of landscape use by gray bats including nightly foraging, migration, and roost switching. The resulting map highlighted 2 major areas of use during spring and fall migration: 3 high likelihood pathways through central Tennessee and 1 primary migration route between northern Arkansas and central Missouri, USA. Although future data could influence the accuracy of this map, the representation in its current form can be used to anticipate bat presence when considering industrial development such as wind turbine siting.

Rediscovery of the critically endangered Hill's horseshoe bat (Rhinolophushilli) and other new records of bat species in Rwanda.

For forty years, there has been growing uncertainty about whether Hill's horseshoe bat (Rhinolophushilli) still persists in Nyungwe National Park, Rwanda. Only known from one small area within the National Park, R.hilli is listed as Critically Endangered by the International Union for the Conservation of Nature (IUCN), based on its extremely small geographic range and presumed low number of mature individuals. Here, we present and describe bat species occurrence data contributed to the Global Biodiversity Information Facility (GBIF) that we collected as part of a long-term collaborative project to rediscover this lost species. This data paper describes the survey methods and findings resulting from cave roost surveys, capture surveys, and acoustic sampling of bat echolocation activity in Nyungwe National Park and surrounding areas in south-western Rwanda from 2013-2020 and their conservation relevance. We report the discovery of an extant population of Hill's horseshoe bat (Rhinolophushilli) in Nyungwe National Park, Rwanda, 40 years since the last reported observation of the species in 1981. We also report the first record of Lander's horseshoe bat (Rhinolophuslanderi) in Nyungwe National Park and the first record of the Damara woolly bat (Kerivoulaargentata) in Rwanda. The dataset contributed to GBIF and described in this paper includes 278 occurrence records from 10 bat species of five families detected at 71 locations in or near Nyungwe National Park, Rwanda. We include a description of the morphological descriptions of R.hilli and present the first acoustic echolocation signatures and phylogenetic information for this species.

Perception at the extreme: Adaptive vocal-motor behavior of bats at high speed flight and in groups

In order to successfully navigate through their environments without collisions at often high speeds, bats rely on two things: successful reconstruction of their environment from returning echoes and motor outputs in response to intermittent sensory information. This depends on the coordination between sensory input and locomotive output. Many bats regularly form dense aggregations in the wild and fly at speeds exceeding 100 km/h, likely posing significant sensorimotor challenges. We recorded the echolocation and flight behavior of wild frequency-modulated (FM) bats as they exited and returned to their cave roost to understand how bats coordinate flight and echolocation when faced with sensory challenges. We found that when exiting the roost in groups, many bats coordinate flight behavior and wingbeat movement with nearby conspecifics, but based on heading delays, this coordination is likely not driven by acoustic cues and instead may be guided by aerodynamic cues. During high-speed roost re-entry, bats modify echolocation signals consistent with increasing object discrimination as they approach the roost, yet adjustments in flight behavior do not coincide with the reception of echoes, suggesting that bats may be combining information from multiple pulses or senses to plan their flight path. [Work supported by ONR N000141612478 and NSF-IIBR-1916850.]

Seasonal variation in age, sex, and reproductive status of Mexican free‐tailed bats

AbstractIn North America, Mexican free‐tailed bats (Tadarida brasiliensis mexicana) consume vast numbers of insects contributing to the economic well‐being of society. Mexican free‐tailed bats have declined due to historic guano mining, roost destruction, and bioaccumulation of organochlorine pesticides. Long‐distance migrations and dense congregations at roosts exacerbate these declines. Wind energy development further threatens bat communities worldwide and presents emerging challenges to bat conservation. Effective mitigation of bat mortality at wind energy facilities requires baseline data on the biology of affected populations. We collected data on age, sex, and reproductive condition of Mexican free‐tailed bats at a cave roost in eastern Nevada located 6 km from a 152‐MW industrial wind energy facility. Over 5 years, we captured 46,353 Mexican free‐tailed bats. Although just over half of the caught individuals were nonreproductive adult males (53.6%), 826 pregnant, 892 lactating, 10,101 post‐lactating, and 4327 nonreproductive adult females were captured. Juveniles comprised 11.5% of captures. Female reproductive phenology was delayed relative to conspecific roosts at lower latitudes, likely due to cooler temperatures. Roost use by reproductive females and juvenile bats demonstrates this site is a maternity roost, with significant ecological and conservation value. To our knowledge, no other industrial scale wind energy facilities exist in such proximity to a heavily used bat roost in North America. Given the susceptibility of Mexican free‐tailed bats to wind turbine mortality and the proximity of this roost to a wind energy facility, these data provide a foundation from which differential impacts on demographic groups can be assessed.

Bat fauna and conservation assessment of Kurdistan caves, Iran

The populations of cave-dwelling bat species are encountering a remarkable decline all over the world. To plan effective conservation projects for bats and their cave roosts, collecting data on their distribution in a particular region is essential. Furthermore, developing an applicable index that incorporates both biotic and abiotic parameters relevant to caves is useful to prioritize caves for conservation management. Recently, there has been a growing interest in studying bat fauna of Iran. The Kurdistan province in west of the country is entirely mountainous, having a suitable geological substratum for formation of caves. Previously, five bat species were reported from Kurdistan. The current study has improved the data by doubling the number of cave-dwelling bat species of the province. A total number of 61 records of 10 species were documented. Overall, of 28 caves studied, 26 caves were used by bats. Each cave hosted one to six bat species. To prioritize Kurdistan caves for conservation programs, the Bat Cave Vulnerability Index (BCVI) was employed for 26 caves explored in this study. Four caves, including Karaftu, Kamtaran, Darvish Ouliya, and Kouna Sham-Sham, were highlighted due to their highest BCVI value. The other 22 caves received medium or low priority values. In the current study, we provided data on the bat fauna of Kurdistan caves, in addition to evaluate their conservation priorities by applying an assessing index for the first time in the country.

The Bats (Chiroptera) of Utila Island, Honduras: species checklist and recommendations to conserve a cave roost

This report catalogues the bats of Utila Island (Honduras) by providing a preliminary checklist of 13 species. We conclusively identified eight primary and five secondary records for bat species on Utila, including three new records that increase the total known species in the Bay Island department to 15. Phyllostomidae was the most represented on Utila, with four genera and six recorded species, followed by Vespertilionidae, two genera and two species, and Emballonuridae, one genus and two species. The families Molossidae, Natalidae, and Noctilionidae each had one species represented. We highlight the ecological importance of bats for the island ecosystem, ongoing threats to their communities and describe a long-term cave roosting site. We aim to raise regional awareness and suggest appropriate conservation action for bats and their habitats on Utila.

Characteristics of Caves Used by Wintering Bats in a Subtropical Environment

AbstractMany cave-roosting bats are declining in number throughout their range because of multiple threats, including disease, disturbance by humans, and habitat loss. Successful conservation of cave-roosting bats requires an understanding of the roles of microclimate, cave structure, and the surrounding landscape on the distribution and abundance of bats, and in particular, the use of winter cave roosts. Cave bats have been well studied in temperate climates, but we know little about these bats in subtropical climates. From 2015 to 2017, we conducted 399 winter surveys of 162 caves in Florida to evaluate factors affecting the presence and abundance of bats at cave roosts. We also determined whether temperatures at these cave roosts were suitable for Pseudogymnoascus destructans, the fungus that causes white-nose syndrome. Across all 3 y, we detected three species of bats: tricolored bat Perimyotis subflavus in 126 (77.8%) caves, southeastern myotis Myotis austroriparius in 51 (31.5%) caves, and a single Rafinesque's big-eared bat Corynorhinus rafinesquii. We analyzed the presence of both tricolored bats and southeastern myotis in caves by using mixed-effects models with a binomial distribution and the number of tricolored bats by using generalized linear mixed-effects models with a Poisson error distribution. Tricolored bat presence was significantly and positively influenced by a cooler cave surface temperature, larger cave entrance size, a single entrance, and the presence of solution holes. Tricolored bat abundance increased in longer, cooler caves that had solution holes, a single, unobstructed entrance, and had no signs of flooding. Southeastern myotis presence was positively associated with longer, domed caves. To be most effective, conservation efforts in subtropical climates should focus on caves with the identified characteristics. More than 90% of caves surveyed each year had a cave interior surface temperature below the upper critical growth limit for P. destructans (19.8°C), indicating that most Florida caves are suitable for growth of P. destructans. Therefore, regular monitoring of winter bat populations in subtropical caves may be important for detecting P. destructans and white-nose syndrome.

Two novel adenoviruses found in Cave Myotis bats (Myotis velifer) in Oklahoma.

Bats are carriers of potentially zoonotic viruses, therefore it is crucial to identify viruses currently found in bats to better understand how they are maintained in bat populations and evaluate risks for transmission to other species. Adenoviruses have been previously detected in bats throughout the world, but sampling is still limited. In this study, 30 pooled-guano samples were collected from a cave roost of Myotis velifer in Oklahoma. A portion of the DNA polymerase gene from Adenoviridae was amplified successfully in 18 M. velifer samples; however, DNA sequence was obtained from only 6 of these M. velifer samples. One was collected in October 2016, one in March 2017, and 4 in July 2017. The October and March samples contained viral DNA that was 3.1% different from each other but 33% different than the novel viral sequence found in the July 2017 samples. Phylogenetic analysis of these fragments confirmed our isolates were from the genus Mastadenovirus and had genetic diversity ranging from 20 to 50% when compared to other bat adenoviruses.

Host ecology moderates the specialization of Neotropical bat-fly interaction networks

The transmission of diseases through parasites is a key mechanism in the regulation of plant and animal populations in ecosystems. Therefore, it is necessary to investigate the relative effect of the variables that can shape the specificity of host-parasite interactions. Previous studies have found that specialization of antagonistic interactions between fly ectoparasites and bats changes according to forest type, host richness, and roosting ecology of bats. In this study, we tested these hypotheses using data from 48 bat communities. In general, our results support previous findings that bat-fly interactions are specialized, resulting in lower niche overlap among bat flies species. In addition, we found that the specificity of bat-fly interactions is lower in tropical mountain forests and is positively related with the richness of bat host species of each study site. Finally, there was a higher bat flies niche overlap in smaller bat-fly interaction networks recorded in bat roosts in caves. We conclude that the roosting ecology of bats could be a key factor to understand the mechanisms related to the horizontal transmission of ectoparasitic flies among bats.

Habitat associations of zoophagic bat ensembles in north-western Australia

North-western Australia comprises the Kimberley Craton and parts of three adjacent sedimentary basins. It has a tropical climate and habitats that range from semiarid plains supporting grasslands to mesic uplands supporting woodlands as well as narrow riparian forests and patches of rainforest; mangrove forests occur along the coast. Its bat fauna comprises three obligate phytophages and 27 obligate zoophages. Analysis of zoophagic bats at 171 sites scattered throughout this study area revealed two compositionally distinct ensembles. One, comprising 19 species, occupies mangrove forest and includes three species known only to occupy mangroves in Western Australia. The other, comprising 20 species, occupies landward habitats and includes four species that are found only in landward ecosystems. Both ensembles are structured in terms of resource allocation, but nestedness observed in assemblage composition can be explained by environmental factors, implying the influence of environmental controls. Sixteen species belong to both ensembles, but seven of these require cave roosts and occur only near cavernous country while three others are confined to rocky riparian habitats. The richest assemblages were recorded in rugged cavernous landscapes in complex vegetation structures near permanent freshwater pools in the most mesic areas.

Corrigendum to: Habitat associations of zoophagic bat ensembles in north-western Australia

North-western Australia comprises the Kimberley Craton and parts of three adjacent sedimentary basins. It has a tropical climate and habitats that range from semiarid plains supporting grasslands to mesic uplands supporting woodlands as well as narrow riparian forests and patches of rainforest; mangrove forests occur along the coast. Its bat fauna comprises three obligate phytophages and 27 obligate zoophages. Analysis of zoophagic bats at 171 sites scattered throughout this study area revealed two compositionally distinct ensembles. One, comprising 19 species, occupies mangrove forest and includes three species known only to occupy mangroves in Western Australia. The other, comprising 20 species, occupies landward habitats and includes four species that are found only in landward ecosystems. Both ensembles are structured in terms of resource allocation, but nestedness observed in assemblage composition can be explained by environmental factors, implying the influence of environmental controls. Sixteen species belong to both ensembles, but seven of these require cave roosts and occur only near cavernous country while three others are confined to rocky riparian habitats. The richest assemblages were recorded in rugged cavernous landscapes in complex vegetation structures near permanent freshwater pools in the most mesic areas.

Long-term research on forest bats: we have the technology

ABSTRACT Long-term research is vital for understanding long-lived, dynamic systems like forests, yet for bats such research is notable for its absence. Recent advances in technology over the last 10–20 years means that long-term studies of bats are viable and can be cost-effective. I outline three case-studies of long-term research on forest bats using different techniques. These involve annual monitoring of populations at cave roosts, periodic monitoring of forest bat activity with ultrasonic detectors and advanced mark-recapture modelling of annual banding data to describe population dynamics. Annual counts over a 17 year period of a large maternity population of Eastern Horseshoe Bats Rhinolophus megaphyllus in a sandstone cave revealed a relatively stable population in the absence of major perturbations. There were only minor variations with climatic fluctuations, suggesting the cave and associated feeding grounds in a high rainfall gully could function as a climate refuge for the species. The second ...

Using passive acoustics to estimate populations of animals in groups

Passive acoustic monitoring is a widely used method to identify animal species and determine spatial and temporal activity patterns. One area where acoustic methods have not yet been successfully applied, however, is in determining population counts. Recently, my lab developed an acoustic method that accurately predicts the count of bats leaving from a cave roost in a given time period. Data were acquired of Brazilian free-tailed bats (Tadarida brasiliensis) across multiple nights and at different cave locations with different roost structures. We used a single microphone to monitor echolocation activity and simultaneously record the emerging bats with thermal and standard video. Bat abundance counts were determined from a single video frame analysis (every 10 sec) and were compared to different energy measures of an acoustic sequence recorded at the time of the analyzed video frame. For most cave locations, linear regression models successfully predicted bat emergence count based on acoustic intensity of the emerging stream, which indicates future population estimates may be collected solely with acoustics. Here, I describe this method and report on its application for counting other animals in groups.

Bats associated to caves in Jalisco, Mexico

Roost selection is important for bats, not only because roosts provide protection against predators but also because they provide stable environmental factors that can help them to optimize their physiological response and maintenance. For a high number of bat species, caves are an extremely important resource, sometimes housing a large number of individuals. In Jalisco, so far have been registered 72 species of bats, which equals 52 % of the bats in the country. However, little is known about which species utilize caves as habitat, including the abundance of their populations. The aims of this study were: 1) to identify some of the main cave roosts for bats in the State of Jalisco, 2) to describe the richness and composition of bat ensembles associated to caves in Jalisco, and 3) to link the distribution of bats among the caves with some environmental factors. Using previous records and references, 21 caves with presence of bats were located and surveyed. We conducted bat captures to identify these species and for those individuals for which their capture was not possible, we used ultrasonic recordings. We estimated the number of individuals using different techniques. A Non-Metric Multidimensional Scaling analysis (NMDS) was used to determine if there is a spatial pattern relationship between bat species and caves. Also, a Canonical Correspondence Analysis (CCA) was conducted to explore which environmental variables explain the spatial pattern of distribution of bats recorded in this study. In the 21 surveyed caves, we found 23 bat species, accounting for 32 % of the bat fauna in Jalisco (six species were identified using ultrasonic calls). The NMDS ordination analysis separated the species of bats in three main groups: one is associated to hot and humid caves, the second included species living in cool and dry caves, and a third group which was related to a cave of higher altitude, associated with temperate habitats. The CCA reported that temperature and humidity of the cave and the altitude as the most important variables for some groups of bats. The richness and abundance of bats were variable among caves and were associated to factors such as the intrinsic requirements of the species, physical conditions of the cave, and to the degree of human disturbance observed in each cave. The association of environmental variables and the presence and the number of bats was statistically significant, particularly with temperature and relative humidity in the case of hot caves, and with altitude for other species of bats. This work contributes to establish a baseline on the knowledge of the cave bats in the State of Jalisco. Some of the caves must be considered as priority for conservation, either for harbor a high number of individual sor a high species richness.

Timing of Cave Emergence and Return in the Dawn Bat (Eonycteris spelaea, Chiroptera: Pteropodidae) in Southern Thailand

The time of emergence of bats from their roosts at dusk and their return was originally described as a circadian rhythm entrained by the time of sunset and sunrise (Erkert 1978). Later, various environmental factors such as ambient light conditions, weather (Frick et al. 2012) and moonlight (Elangovan and Marimuthu 2001; Thies et al. 2006) were considered to influence bat activity. Bats emerging before dark or during bright moonlight in­ creases their risk of predation by raptorial birds and they avoid such situations (Welbergen 2006). However insecti­ vorous bats often risk predation to increase foraging opportunities when their prey is available in abundance at dusk (Jones and Rydell 1994; Rydell et al. 1996; Duverge et al. 2000). Besides environmental factors, foraging efforts differ between male and female mammals according to the energetic requirements of reproduction (Bronson 1985). Breeding females allocate more time and energy to for­ aging to meet the energy demands of growing pups (McCracken and Wilkinson 2000; Racey and Entwistle 2000; Barclay and Harder 2003). In contrast, reproduc­ tive males spend time and energy in defending females or resources useful to them in order to achieve mating suc­ cess with multiple females (Clutton­Brock 1989). In fruit bats, roost emergence and return times of adult males often differ compared with other reproductive categories, especially during the breeding period. For example, adult males of Old World tent­making (e.g., Cynopterus sphinx) and cavity roosting fruit bats (e.g., Balionycteris maculata) spend less time away from the roost for­ aging and more time at the roost (Balasingh et al. 1995; Marimuthu et al. 1998; Hodgkison et al. 2003). Adult male Rousettus aegyptiacus and Pteropus tonganus emerge after adult females (Korine et al. 1994; Banack and Grant 2003). Similar patterns were found in neotropical fruit bats such as Artibeus jamaicensis (Morrison and Morrison 1981) and A. lituratus (Munoz­Romo et al. 2008). In Southeast Asia, Eonycteris spelaea roosts in caves and travels over tens of kilometres to access food sources (Start 1974). It is the principal pollinator of economi­ cally important crops like durian (Durio zibethinus), a leguminous canopy tree Parkia spp. and the Indian trumpet flower (Oroxylum indicum) in managed agri­ cultural habitats in southern Thailand (Bumrungsri et al. 2008, 2009; Srithongchuay et al. 2008). Eonycteris spelaea reproduces year round (Beck and Lim 1973; Bhat et al. 1980; Heideman and Utzurrum 2003). In a previous study, a capture survey at a cave entrance suggested a high proportion of mature males return during the early hours of the night (Bumrungsri et al. 2013). We investigated the emergence and return time of the dawn nectar bat, E. spelaea, using radio­telemetry to record the time of cave emergence and return by E. spelaea of known sex and reproductive status. We hy­ pothesized differential foraging durations between adult male E. spelaea and other reproductive categories.

Discovery of new colonies of the rare Wroughton’s Free-tailed Bat Otomops wroughtoni (Mammalia: Chiroptera: Molossidae) in Meghalaya, northeastern India

Otomops wroughtoni is an extremely rare molossid bat, known so far by a single breeding colony in southwestern India and two single individuals recorded in Meghalaya and Cambodia. We report here the discovery of three new roosts located in large karstic caves of the Jaintia Hills, in southeastern Meghalaya. Visual counts indicate that at least 90 individuals occupied these new roosts in February 2014, which doubles the known world population of this species. The new populations of Wroughton’s Free-tailed Bats from the Jaintia Hills have considerable value for the conservation of this elusive species. Although these bats are protected under national laws, their cave roosts and hunting habitats are subjected to severe and ongoing degradation. A protection plan that would include more extensive surveys and a strict conservation of these caves should be implemented rapidly to mitigate these threats.

The conservation status of bats in Fiji

AbstractBats provide important ecosystem services throughout the South Pacific but many species are threatened. The Fiji archipelago has a rich bat fauna yet few arrangements exist to promote the conservation of this group. From July 2008 to March 2011 we visited important sites identified in previous surveys for bats on Vanua Levu, Taveuni, Viti Levu and the Yasawa Islands. We netted and recorded five of Fiji's six bat species (Pteropus tonganus, Pteropus samoensis nawaiensis, Notopteris macdonaldi, Chaerephon bregullae and the Critically Endangered Mirimiri acrodonta). This was only the sixth recorded capture of M. acrodonta. P. tonganus is widespread in Fiji and exploits many different environments. P. samoensis nawaiensis mostly uses forested areas, and large tracts of forest are required for its long-term protection. Cave protection is vital for the two insectivorous species (C. bregullae and Emballonura semicaudata) and N. macdonaldi. In particular, the Nakanacagi maternity site remains globally significant for C. bregullae. E. semicaudata was not caught or detected during our surveys. It appears to be extinct from most large islands in Fiji and has abandoned the only large cave roost (Yaqeta) observed 10 years ago. This species has disappeared from or declined dramatically on Vanuatu, Samoa, Tonga and Fiji. We recommend that the category of E. semicaudata semicaudata on the IUCN Red List be changed to Critically Endangered. Management priorities should focus on community engagement and education, and improved cave and forest management and protection.

Winter diet analysis in Rhinolophus euryale (Chiroptera)

Abstract We investigated the winter food of Mediterranean horseshoe bats (Rhinolophus euryale) in four winter cave roosts in southern Slovakia and northern Hungary and investigated the relationship between food and ambient temperature. The bats were active during the whole winter period and they produced excrement throughout the entire hibernation period, even when outside temperatures dropped below zero. The guano was in two forms, containing (1) prey items and (2) non-prey items. The identifiable items belonged to lepidopteran species, but only one was identified, on the basis of the genital fragments, the moth Colotois pennaria, which was the main prey species in autumn and early winter. Our results shed light on the extraordinarily high level of activity in this bat species during winter hibernation, which in temperate regions is a strategy that enables bats to survive when prey is reduced or absent. In R. euryale, the torpor in the course of hibernation is not continuous and our results help to explain how energy losses caused by bat movements are covered.