Rafinesque's Big-eared Bat Research Articles

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.

Seasonal Changes in the Active Bat Community of the Kisatchie National Forest, Louisiana

Few North American studies have quantified differences in bat community composition between summer and winter. In southerly regions, especially the coastal plain of the Gulf of Mexico, winters are mild and experience only short periods of freezing weather annually. In regions such as this, there may be a substantive community of bats that are active in the winter. We examined seasonality of the bat community in the Kisatchie National Forest of Louisiana. We mist-netted bats for 130 nights during winter and 51 nights during summer and caught 200 and 190 bats, respectively, from 10 different species. Corynorhinus rafinesquii (Rafinesque's Big-eared Bat), Lasiurus borealis (Eastern Red Bat), and Lasionycteris noctivagans (Silver-haired Bat) were more frequently captured in winter, all other species were captured more frequently in summer. Significant differences existed between summer and winter in species richness and abundance of bats, but not for Shannon's diversity index. Across the entire year and in winter, more bats were caught on nights with higher temperature than on nights with lower temperatures. Although there was much temporal variation in species composition, we found a substantial bat community that is active in the winter in the Kisatchie National Forest of Louisiana.

Refining the Distribution of Rafinesque's Big-Eared Bat in Florida

Corynorhinus rafinesquii (Rafinesque's Big-eared Bat) is uncommon and unevenly distributed throughout its range, and its populations are believed to be declining. The distribution in Florida, the southernmost extent of the range, is unclear, and recently published maps show records in only 16 counties scattered across the state. We compiled published and unpublished records of Rafinesque's Big-eared Bat in Florida and found 59 total records, including records from 13 counties where the species had not been previously reported. These new records expand the known distribution in Florida to 29 counties, including Miami-Dade County in extreme southeastern Florida. Our compilation of records clarifies the species' distribution in Florida, but several broad geographic areas still lack records despite the presence of forested wetland habitat potentially suitable for Rafinesque's Big-eared Bat. We recommend further survey efforts for Rafinesque's Big-eared Bat in 4 areas we identified where the species may be present.

Preserving connectivity under climate and land-use change: No one-size-fits-all approach for focal species in similar habitats

Habitat connectivity is essential for maintaining populations of wildlife species, especially as climate changes. Knowledge about the fate of existing habitat networks in a changing climate and in light of land-use change is critical for determining which types of conservation actions must be taken to maintain those networks. However, information is lacking about how multiple focal species that use similar habitats overlap in the degree and geographic patterns of threats to linkages among currently suitable habitat patches. We sought to address that gap. We assessed climate change threat to existing linkages in the southeastern United States for three wildlife species that use similar habitats but differ in the degree to which their ranges are limited by climate, habitat specificity, and dispersal ability. Linkages for the specialist species (timber rattlesnake), whose range is climate-restricted, were more likely to serve as climate change refugia – that is, they were more likely to be climate-stable – by the middle of the 21st century. This contrasts with the two more generalist species (Rafinesque's big-eared bat and American black bear), whose linkages were threatened by climate change and thus required adaptation measures. Further incorporation of projected land-use change and current protection status for important linkages narrows down our recommended conservation actions for each species. Our results highlight the surprising ways in which even species that use similar habitats will experience differences in the degree and geographic patterns of threats to connectivity. Taking action before these projected changes occur will be critical for successful conservation.

Winter habitats of bats in Texas.

Few studies have described winter microclimate selection by bats in the southern United States. This is of particular importance as the cold-adapted fungus, Pseudogymnoascus destructans, which causes the fatal bat disease white-nose syndrome (WNS), continues to spread into southern United States. To better understand the suitability of winter bat habitats for the growth of P. destructans in this region, we collected roost temperature and vapor pressure deficit from 97 hibernacula in six ecoregions in Texas during winter 2016-17 and 2017-18. We also measured skin temperature of Rafinesque's big-eared bats (Corynorhinus townsendii), Townsend's big-eared bats (C. townsendii), big-brown bats (Eptesicus fuscus), southeastern myotis (Myotis austroriparius), cave myotis (M. velifer), tri-colored bats (Perimyotis subflavus), and Mexican free-tailed bats (Tadarida brasiliensis) during hibernation to study their use of torpor in these habitats. We found that temperatures within hibernacula were strongly correlated with external air temperatures and were often within the optimal range of temperatures for P. destructans growth. Hibernacula and skin temperatures differed among species, with Rafinesque's big-eared bats, southeastern myotis, and Mexican free-tailed bats occupying warmer microclimates and having higher torpid skin temperatures. For species that were broadly distributed throughout Texas, hibernacula and skin temperatures differed within species by ecoregion; Tri-colored bats and cave myotis in colder, northern regions occupied colder microclimates within hibernacula and exhibited colder skin temperatures, than individuals of the same species in warmer, southern regions. These data illustrate the variability in microclimates used as hibernacula by bats in Texas and suggest similar variation in susceptibility to WNS in the state. Thus, monitoring microclimates at winter roosts may help predict where WNS may develop, and where management efforts would be most effective.

Adaptive response to land-use history and roost selection by Rafinesque’s big-eared bats

Although habitat loss and degradation are major contributors to species declines, some species are able to adapt to changes in land use by selecting different habitats or structures in disturbed areas than they do in more pristine habitats. Bats are particularly vulnerable to changes in land use due to their dependence on specific habitat types and structures. The objective of this study was to determine how selection and use of roost trees, and niche breadth of Rafinesque's big-eared bats (Corynorhinus rafinesquii) varied with land-use history. I examined use and selection of roosts at 3 bottomland hardwood sites that varied in amount and time since timber harvest. Fortynine transects were established as a means of searching for bats in trees with basal cavity openings and were surveyed 2–9 times. Bats at the most-disturbed sites exhibited the broadest niches, using a greater number of tree species and habitat types, although bats at the least-disturbed site used a broader range of cavity volumes. Cavity characteristics were the primary factors governing roost selection by Rafinesque's big-eared bats, but selection varied among sites. Probability of use increased with increasing cavity volume for bats at all sites, but bats at the most-disturbed site primarily used trees in the smallest cavity volume class, whereas bats at the least-disturbed site primarily used trees in the largest cavity volume class. Results of this study suggest that Rafinesque's bigeared bats can adapt to a range of habitat conditions if trees with large cavities are available. However, future studies need to determine the long-term viability of this species in disturbed habitats.

Evolution and Cryo-electron Microscopy Capsid Structure of a North American Bat Adenovirus and Its Relationship to Other Mastadenoviruses.

Although many adenoviruses are host specific and likely codiverged with their hosts over millions of years, other adenoviruses appear to have emerged through successful cross-species transmission events on more recent time scales. The wide geographic distribution and genetic diversity of adenoviruses in bats and their close phylogenetic relationship to Canine mastadenovirus A (CAdV A) has raised important questions about how CAdV A, and possibly other mammalian adenoviruses, may have emerged. Although most adenoviruses tend to cause limited disease in their natural hosts, CAdV A is unusual in that it may cause high morbidity and sometimes fatal infections in immunocompetent hosts and is thus an important pathogen of carnivores. Here, we performed a comparative evolutionary and structural study of representative bat and canine adenoviruses to better understand the relationship between these two viral groups.

Prey Size and Dietary Niche of Rafinesque's Big-Eared Bat (Corynorhinus rafinesquii)

Abstract Bats in the genus Corynorhinus possess a suite of morphological characters that permit them to effectively use both gleaning and aerial-hawking foraging strategies to capture Lepidoptera. Consequently, they occupy a specialized feeding niche within North American bat assemblages and are of particular interest for dietary studies. We collected fecal pellets from a colony of C. rafinesquii (Rafinesque's Big-Eared Bat) at Mammoth Cave National Park during August–October 2011 and amplified cytochrome-c oxidase subunit 1 fragments of prey from these pellets. We used the Barcode of Life Database to identify prey, and evaluated the size of prey species based on published values. The mean wingspan of prey we recorded from our samples was smaller than average values reported for Rafinesque's Big-Eared Bat using traditional methods (P ≤ 0.01), suggesting that surveys of culled insect parts beneath roosting sites may lead to biased estimates of the size and breadth of prey species eaten by gleaning bats. Me...

Molecular detection of the causative agent of white-nose syndrome on Rafinesque's big-eared bats (Corynorhinus rafinesquii) and two species of migratory bats in the southeastern USA.

Pseudogymnoascus destructans, the causal agent of white-nose syndrome (WNS), is responsible for widespread mortality of hibernating bats across eastern North America. To document P. destructans exposure and infections on bats active during winter in the southeastern US, we collected epidermal swabs from bats captured during winters 2012-13 and 2013-14 in mist nets set outside of hibernacula in Tennessee. Epidermal swab samples were collected from eight Rafinesque's big-eared bats (Corynorhinus rafinesquii), six eastern red bats (Lasiurus borealis), and three silver-hair bats (Lasionycteris noctivagans). Using real-time PCR methods, we identified DNA sequences of P. destructans from skin swabs of two Rafinesque's big-eared bats, two eastern red bats, and one silver-haired bat. This is the first detection of the WNS fungus on Rafinesque's big-eared bats and eastern red bats and the second record of the presence of the fungus on silver-haired bats.

Roost Selection by Rafinesque's Big-Eared Bats (Corynorhinus rafinesquii) in a Pristine Habitat at Three Spatial Scales

Although several studies have described roost use by Rafinesque's big-eared bats (Corynorhinus rafinesquii), few studies have examined roost selection. We examined roost use and selection by Rafinesque's big-eared bat at the tree, stand, and landscape scales during the maternity season in pristine old-growth habitat in the Coastal Plain of South Carolina. We located 43 roosts (14 maternity, 29 solitary) through cavity searches and radio-telemetry. Maternity colonies and solitary individuals selected roosts based on similar characteristics. The best model explaining roost selection by all bats included tree and stand characteristics; landscape factors had little influence on roost use. Bats selected large diameter trees in areas with a high density of trees with cavities in the surrounding area. Most roosts (67.4%) were in water tupelo (Nyssa aquatica) in semi-permanently flooded and saturated areas. Half of maternity roost cavities had upper bole openings whereas only 25.8% of solitary roosts had upper bo...

Diet of Rafinesque's Big-Eared Bat (Corynorhinus rafinesquii) in West-Central Louisiana

We investigated the diet of Corynorhinus rafinesquii (Rafinesque's Big-eared Bat) in west-central Louisiana by examining fecal pellets collected from beneath 3 bridges used by these bats as day roosts. Fresh fecal material was found under the bridges during every month of the year. We detected 5 insect orders, including 5 families, in fecal pel- lets collected from 25 August 2005 to 5 January 2007. Lepidoptera represented 93.7% of the total volume and was the only order observed in 100% of our samples. Coleopterans, mostly Scarabaeidae, were the second most abundant food item and represented 5.8% of the total volume. Hemiptera, Diptera, and Hymenoptera together represented 0.4 % of the total volume. We observed Diptera, Hemiptera, Hymenoptera, and Coleoptera in fecal pel- lets collected under some, but not all bridges. No insect orders were observed that had not previously been reported as prey of Rafinesque's Big-eared Bats. Our results were similar to those reported in studies conducted in Kentucky, North Carolina, and Florida, and we concluded that Rafinesque's Big-eared Bats primarily prey upon lepidopterans in Louisiana.

Roosts of Rafinesque's Big-Eared Bats and Southeastern Myotis in East Texas

Abstract Because diurnal roosts can be important in determining bat occupancy and abundance in forested habitats, we identified characteristics of cavity trees that influence roost selection by Corynorhinus rafinesquii (Rafinesque's Big-eared Bats) and Myotis austroriparius (Southeastern Myotis) in east Texas. We identified used and non-used cavity trees with a combination of transect searches, radiotelemetry, and historical records at 7 study areas. Both bat species selected similar cavity trees for summer diurnal roosts, showing an affinity for tupelo trees (Nyssa spp.), with 55% of diurnal roosts in Nyssa aquatica (Water Tupelo) and 33% in N. sylvatica (Blackgum). Of 17 tree and habitat variables we measured at used and unused cavity trees, those related to cavity size and availability (cavity height and diameter, tree diameter, density of large trees in the area) were the most important predictors of use. Characteristics of the surrounding stand at both local and landscape scales were less important. ...

Effects of reproductive condition, roost microclimate, and weather patterns on summer torpor use by a vespertilionid bat

A growing number of mammal species are recognized as heterothermic, capable of maintaining a high-core body temperature or entering a state of metabolic suppression known as torpor. Small mammals can achieve large energetic savings when torpid, but they are also subject to ecological costs. Studying torpor use in an ecological and physiological context can help elucidate relative costs and benefits of torpor to different groups within a population. We measured skin temperatures of 46 adult Rafinesque's big-eared bats (Corynorhinus rafinesquii) to evaluate thermoregulatory strategies of a heterothermic small mammal during the reproductive season. We compared daily average and minimum skin temperatures as well as the frequency, duration, and depth of torpor bouts of sex and reproductive classes of bats inhabiting day-roosts with different thermal characteristics. We evaluated roosts with microclimates colder (caves) and warmer (buildings) than ambient air temperatures, as well as roosts with intermediate conditions (trees and rock crevices). Using Akaike's information criterion (AIC), we found that different statistical models best predicted various characteristics of torpor bouts. While the type of day-roost best predicted the average number of torpor bouts that bats used each day, current weather variables best predicted daily average and minimum skin temperatures of bats, and reproductive condition best predicted average torpor bout depth and the average amount of time spent torpid each day by bats. Finding that different models best explain varying aspects of heterothermy illustrates the importance of torpor to both reproductive and nonreproductive small mammals and emphasizes the multifaceted nature of heterothermy and the need to collect data on numerous heterothermic response variables within an ecophysiological context.

Divergent Roosting Habits of Rafinesque's Big-eared Bat and Southeastern Myotis During Winter Floods

Despite the importance of winter roosts to bat ecology, much less is known about tree roosts used by bats in winter than in summer. Rafinesque's big-eared bat (Corynorhinus rafinesquii) and southeastern myotis (Myotis austroriparius) are species of concern whose winter tree roost selection may be constrained by seasonal flooding in cypress-gum swamps. To evaluate winter roost selection by these species, we compared characteristics of winter roosts to trees not occupied in winter and to summer roost trees in the Oconee River floodplain, Laurens County, Georgia. We located 23 Rafinesque's big-eared bat winter roosts and 5 southeastern myotis winter roosts by climbing and visually inspecting hollow trees and by radio telemetry. We analyzed differences between used and unused trees in winter and between winter and summer roosts. Despite extensive flooding in winter, Rafinesque's big-eared bats roosted in cypress-gum swamps in summer and winter. Accordingly, they used similar large hollow water tupelo (Nyssa aquatica) in both seasons, although roost entrances were higher in winter. In contrast, southeastern myotis roosted in cypress-gum swamps in summer and switched to a diverse hardwood floodplain forest with shallower flood waters in winter. As a result they used smaller roosts in different tree species in winter than in summer. The divergent roosting habits in winter are likely due to the height of roost entrances in relation to flood waters. In summer Southeastern myotis use basal openings that are submerged during winter flooding, whereas Rafinesque's big-eared bats use openings located higher on the tree bole that are not submerged. Therefore, management for southeastern myotis may require provision of separate summer and winter roosting habitats.

Multi-scale Roost Site Selection by Rafinesque's Big-eared Bat (Corynorhinus rafinesquii) and Southeastern Myotis (Myotis austroriparius) in Mississippi

Abstract Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM) are species of concern whose current population statuses are unknown. Bottomland hardwood forests are important roosting habitat for RBEB and SEM; however, ≥80% of these forests have been cleared or degraded in Mississippi. Limited information on roost site requirements exists across either species ranges; therefore, we conducted roost surveys for RBEB and SEM in bottomland and riparian hardwood forests on Noxubee National Wildlife Refuge, Legion State Park, and Tombigbee National Forest, Mississippi, during winter 2009–2010 and spring 2010. To compare seasonal roost selection for each species we compared tree species, used 95% confidence intervals (CIs) for three tree variables [diameter at breast height (DBH), cavity volume, and opening area] and logistic regression for four landscape variables (elevation, slope, distance to nearest stream, and distance to nearest road). We used Aka...

Probability of Detection and Visual Count Error for Rafinesque's Big-eared Bat (Corynorhinus rafinesquii) and Southeastern myotis (Myotis austroriparius) in Tree Cavities

A common error in many studies is that a species may go undetected when they are actually present, thus leading to underestimates of the true population. Because imperfect detection can affect population estimates, we calculated detection probabilities of two rare bat species, Rafinesque's big-eared bats (Corynorhinus rafinesquii; RBEB) and southeastern myotis (Myotis austroriparius; SEM), when roosting in tree cavities. We used two methods: repeated surveys of the same tree cavity and a removal method where a tree cavity was eliminated from future surveys after a bat was detected. When repeated surveys were conducted, detection probabilities were 95% for each observer and 100% for two observers combined (n = 43). Using the removal method, each observer independently detected bats in tree cavities in 92% of inspections; whereas, combined observations of two surveyors improved detection probability to 99% (n = 27). We also evaluated count error for species identification and abundance using a two-observer method and compared it to digital infra-red imagery. Count errors were typically <4% and 38% when ≤20 bats and >20 bats were present, respectively, compared to digital images. When count errors occurred, most (64–73%) underestimated the number of bats present. Observers correctly identified species on 91% of occasions. Video recording tree cavities improved estimates of bat abundance and verified species composition. Repeated surveys and the removal method were similarly effective and suitable techniques for monitoring bat species occurrence; however, visual surveys were accurate for estimating abundance when number of bats was ≤20.

Summer heterothermy in Rafinesque’s big-eared bats (Corynorhinus rafinesquii) roosting in tree cavities in bottomland hardwood forests

Many small mammals are heterothermic endotherms capable of maintaining an elevated core body temperature or reducing their thermoregulatory set point to enter a state of torpor. Torpor can confer substantial energy savings, but also incurs ecological costs, such as hindering allocation of energy towards reproduction. We placed temperature-sensitive radio transmitters on 44 adult Rafinesque's big-eared bats (Corynorhinus rafinesquii) and deployed microclimate dataloggers inside 34day roosts to compare the use of torpor by different sex and reproductive classes of bats during the summer. We collected 324 bat-days of skin-temperature data from 36 females and 4 males. Reproductive females employed fewer torpor bouts per day than non-reproductive females and males (P<0.0001), and pregnant and lactating females had higher average (P<0.0001) and minimum (P<0.0001) skin temperatures than non-reproductive females. Pregnant females spent less time torpid (P<0.0001) than non-reproductive females, but lactating females used relatively deep, long torpor bouts. Microclimates varied inside tree species with different configurations of entrances to the roost cavity (P<0.0001). Bats spent more time torpid when roosting in water tupelo (Nyssa aquatica) trees possessing only a basal entrance to the cavity (P=0.001). Of the tree species used as roosts, water tupelo cavities exhibited the least variable daytime and nighttime temperatures. These data demonstrate that use of summer torpor is not uniform among sex and reproductive classes in Rafinesque's big-eared bat, and variation in microclimate among tree roosts due to species and structural characteristics facilitates the use of different thermoregulatory strategies in these bats.

Estimating density of a forest‐dwelling bat: a predictive model for Rafinesque's big‐eared bat

Data on species distribution and abundance are the foundation of population ecology. However, due to difficulties in surveying bats, abundance estimates for tree-roosting microchiropterans are non-existent. Therefore, our objective was to develop methods for estimating colony abundance and density, taking as our model Rafinesque's big-eared bat Corynorhinus rafinesquii, a species of conservation concern found in cypress-gum swamps of the southeastern United States. We searched 123 transects at eight study sites in the Coastal Plain of Georgia, USA to locate and characterize diurnal summer roosts of C. rafinesquii. We modeled the relationship between the number of bat colonies and landscape-scale habitat variables with zero-inflated negative binomial regression and used Akaike's information criterion to select the most parsimonious models. We generated a predictive density map to identify areas of high colony density and to estimate overall abundance. Colony density was predicted by the duration of wetland flooding, wetland width, and study site. Application of the regression model to a GIS indicated there were 3,734 colonies containing 6,910 adult bats on the eight study sites. Predicted density ranged from 0.07 colonies/ha and 0.07 adult bats/ha in saturated wetlands to 0.47 colonies/ha and 1.18 adult bats/ha in semi-permanently flooded wetlands. This study is the first to estimate density and abundance of forest-dwelling microchiropterans over a large area. Such data can serve as a baseline for future work on population trends in C. rafinesquii. In addition, our approach could be replicated for other bat species with moderately cryptic roosts.

Observations of Parturition in Rafinesque's Big-Eared Bats (Corynorhinus rafinesquii) Beneath a Concrete Bridge

Abstract We report on observations of parturition and maternal behavior of Corynorhinus rafinesquii (Rafinesque's Big-eared Bat) at a bridge in west-central Mississippi. Rafinesque's Big-eared Bats formed a maternity colony beneath the bridge in March, and parturition occurred from late May to early June. On 28 May 2004, a female Rafinesque's Big-eared Bat was observed giving birth in the breech position, which has not been previously reported for the species. On the same day, another adult female and her pup were found struggling on the ground due to entanglement of the umbilical cord around the mother's wing, and a third female was observed biting her pup. While important data were obtained during our observations, we emphasize the necessity of using extreme care when conducting repeated surveys at maternity roost sites.

Intra- and Interspecific Responses to Rafinesque's Big-Eared Bat (Corynorhinus rafinesquii) Social Calls

Bats respond to the calls of conspecifics as well as to calls of other species; however, few studies have attempted to quantify these responses or understand the functions of these calls. We tested the response of Rafinesque's big-eared bats (Corynorhinus rafinesquii) to social calls as a possible method to increase capture success and to understand the function of social calls. We also tested if calls of bats within the range of the previously designated subspecies differed, if the responses of Rafinesque's big-eared bats varied with geographic origin of the calls, and if other species responded to the calls of C. rafinesquii. We recorded calls of Rafinesque's big-eared bats at two colony roost sites in South Carolina, USA. Calls were recorded while bats were in the roosts and as they exited. Playback sequences for each site were created by copying typical pulses into the playback file. Two mist nets were placed approximately 50–500 m from known roost sites; the net with the playback equipment served as the Experimental net and the one without the equipment served as the Control net. Call structures differed significantly between the Mountain and Coastal Plains populations with calls from the Mountains being of higher frequency and longer duration. Ten of 11 Rafinesque's big-eared bats were caught in the Control nets and, 13 of 19 bats of other species were captured at Experimental nets even though overall bat activity did not differ significantly between Control and Experimental nets. Our results suggest that Rafinesque's big-eared bats are not attracted to conspecifics' calls and that these calls may act as an intraspecific spacing mechanism during foraging.