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Summer habitat for the female Tricolored Bat (Perimyotis subflavus) in Tennessee, United States
Abstract
The Tricolored Bat is an imperiled species due to white-nose syndrome. There is limited information available on roosting and foraging area use of the species to support planning and management efforts to benefit recovery in the Southeastern United States. Female tricolored bats exit hibernation and allocate energy toward disease recovery, migration, and reproduction. Providing and managing for summer habitat is 1 strategy to promote recovery. We sought to: (1) determine local- and landscape-scale factors that influence female Tricolored Bat roost selection; (2) quantify land cover use in core and overall foraging areas; and (3) define foraging area size and distances traveled by female tricolored bats in Tennessee. Bats in this study roosted in trees of variable sizes, in multiple tree species with large canopy volumes, and almost always roosted in trees with dead leaf foliage suspended in the canopy. Forest plots used by bats had trees averaging 30 cm diameter at breast height, basal areas averaging 27 m2/ha, contained multiple tree species, and comprised around a 50:50 ratio of canopy and subcanopy trees. Bats did not roost in coniferous forest areas and were only located in deciduous and mixed forest areas. Bats foraged near and directly over water, in open areas, and along forest edges. This study increases our knowledge on habitat requirements of the species in a temperate region dominated by unfragmented forests and many large water bodies and serves a baseline for management and efforts to benefit survival, reproduction, and population recovery.
... These results suggest low predictive power and that there were unmeasured habitat variables that might play a significant role at the landscape scale. For instance, it is known the water availability is crucial for this insectivorous species (Fujita and Kunz 1984;Cable and Willcox 2024); however, water availability did not differ across the landscape as streams were plentiful across the study area. It is likely that water would be a driving factor for roost site selection, but perhaps at a different scale than measured in this analysis. ...
... Understanding tricolored bat summer habitat use, and more specifically roost selection, is critical for conservation of this species across its range. All roosts were live, healthy trees with a low decay stage, while available trees had a wide variety of decay stages; this concurs with previous work by (Shute et al. 2021;Cable and Willcox 2024) on tricolored bats in the southeast, but is contrary to other research by (Loeb and O'Keefe 2006). Individuals used trees with canopy density (mean = 86.2%) ...
... and a tree diameter at breast height (mean = 51.9 cm) similar to other studies within the southeastern US (Loeb and O'Keefe 2006;Shute et al. 2021;Cable and Willcox 2024). At the roost tree and stand scale, we found that tree height, compared to all other habitat variables, was the best predictor of roost selection. ...
Summer habitats are critical to bat population persistence as they support multiple life history stages, including maternity colonies, nursery sites, and foraging locations. The tricolored bat ( Perimyotis subflavus ) is a hibernating North American bat species that uses forested landscapes during summer months; however, information on the summer habitat requirements is limited. The objective of this work was to quantify the characteristics of roost sites selected by tricolored bats during summer months. We captured, tagged, and tracked 15 bats using radio-telemetry to 55 roost locations. At each roost, we recorded roost habitat characteristics and other forest characteristics within a 0.1 ha circular plot surrounding the roost tree and a 1 km buffer at the landscape scale. We repeated these measurements for three random trees per roost tree to characterize available habitat for selection. We used a suite of mixed conditional logistic regression models to test multiple factors known to influence roost-site selection for various bat species and compared using Akaike information criterion to select the best model. The top model at the roost scale demonstrated that roost selection was influenced by roost tree height, while the landscape scale was influenced by deciduous forest and distance to roads. There is a critical information gap for the ongoing recovery of tricolored bats; better understanding of summer habitat and proper forest management implications, as well as information on scale-specific habitat selection, is needed to better understand tricolored bat management needs.
... We conducted harp-trap (Bat Conservation and Management, Inc.) surveys to capture bats at four summer roosting sites in Tennessee, (TN), USA: a cave in Hawkins County (Site 1; 632 m from closest major road with 2 cars or more/minute daily traffic; 0% urban development in surrounding 500 m radius), an unfinished concrete nuclear facility in Hawkins County (Site 2; 3,584 m from closest major road; 24% urban development in surrounding 500 m radius), a cave in Meigs County (Site 3; 583 m from closest major road; 0% urban development in surrounding 500 m radius), and a cave in Montgomery County (Site 4; 5,063 m from closest major road; 0% urban development in surrounding 500 m radius) (Fig 1). Distance to closest major road and urbanization metrics were extracted from Geographic Information System layers created from a previous study [21]. Sites 1 and 4 are heavily used by M. grisescens in the summer and winter and Sites 2 and 3 are known to be primarily used during the summer season. ...
We observed multiple gray bats (Myotis grisescens) in 2022 with large patches of fur loss (i.e., alopecia) on the dorsal surface of their body. Alopecia in wildlife has been linked to multiple possible factors and often is a sign of suboptimal health. In 2023, we designed an experiment to compare prevalence of alopecia in gray bats across various reproductive stages, characterize the severity of alopecia lesions, and determine the ectoparasites and microbiota present on the regions of fur loss. We harp-trapped four summer gray bat roosts 2–3 times between 11 April–30 August 2023 and collected skin swabs and scrapes from each bat with alopecia. We determined the severity of the alopecia lesions on a scale 0–7 by summing the degree of redness (0–2), skin condition (0–1), and percentage of fur loss (0–4). We cultured the skin swabs for fungal and bacterial growth and examined skin scrapes under a microscope to determine the presence of subcutaneous mites. We found no evidence that subcutaneous mites cause the fur loss. We determined that prevalence of alopecia in M. grisescens varies throughout the summer. Prevalence is highest for female bats that are or recently were lactating, reaching an average of 6% ± 6 SD (0–15% range) of captured females exhibiting fur loss during the pup rearing period. Alopecia is most prevalent in male bats in early summer (1% ± 2 SD; 0–4% range). Lactating females had more severe cases than males and were often associated with skin redness due to unknown causes. Bats with alopecia did not differ in body condition, determined from body mass, from bats without alopecia. Future studies could investigate the role of stress in possible autoimmune responses contributing to alopecia. Conservation strategies aimed at reducing stress and supporting nutritional requirements during the summer are likely beneficial to M. grisescens.
... We calculated the percentage of each class within a 1-km buffer around each site (Appendix Table A2). The 1-km buffer roughly approximates the mean foraging home range sizes of our species of interest, which range from 102 to 622 ha (Wilkinson and Barclay, 1997;Coleman et al., 2014a;Divoll et al., 2022;Thorne et al., 2021;Cable and Wilcox, 2024). All covariates except survey year were scaled prior to fitting models, by subtracting the mean and dividing by the standard deviation. ...
Appropriately monitoring vulnerable species is essential for resource management decision-making. We used two different metrics (occupancy and acoustic activity) to evaluate population trends of North American bats susceptible to a fungal disease and compared the outcomes of these two analyses. Our dataset consisted of passive acoustic survey data collected at nine U.S. national parks in the Great Lakes region between 2016 and 2020. Our focal species were little brown bat (Myotis lucifugus), northern long-eared bat (Myotis septentrionalis), tricolored bat (Perimyotis subflavus), and big brown bat (Eptesicus fuscus). Combining acoustic detection data with site-specific and environmental covariates, we developed park-and species-specific models of occupancy (use) and acoustic activity. For little brown, northern long-eared, and tricolored bats, probability of use declined 20 % and activity declined 66 %, on average. For big brown bat, probability of use decreased 9 % and activity increased 17 %. Our results showed that use of space and level of activity were not predicted by the same covariates but were positively related. We also found probability of use could remain high while activity decreased to relatively low levels. Although we observed precipitous declines in activity rates of three species, they were still using a high proportion of the landscape. We conclude that analyzing activity provides different but complementary information to analyzing species' use of space. The two metrics vary on different temporal and spatial scales and have different biases. Appropriate choice of which parameter to analyze is crucial, as different parameters may lead to different ecological conclusions, thus affecting how management decisions are made and how species conservation and recovery efforts are implemented.
Bats are important components of global ecosystems, providing essential ecosystem services with substantial economic benefit. Yet North American bat populations have been negatively affected by numerous factors (e.g., disease, habitat loss, wind energy development) with compounding effects. Bats use habitats at a variety of scales, from small, isolated patches to large, contiguous corridors. Landscape-level research is necessary to identify important habitats, patches, and corridors to strategically target management interventions. We created habitat suitability models (HSMs) for hoary bats (Lasiurus cinereus), eastern red bats (L. borealis), and tri-colored bats (Perimyotis subflavus) across Illinois, USA, using species-specific landscape and climate variables. With the 3 models from this study and a previously published HSM for Indiana bats (Myotis sodalis), we stacked binary HSMs, thereby identifying priority conservation areas across Illinois. Species exhibited different distributional patterns and habitat preferences across Illinois. Multi-species HSMs highlight high quality habitat (i.e., ecologically important habitat that provides preferred resources for roosting, foraging, and raising young) in southern Illinois and along river riparian areas. This approach identified priority conservation areas mainly following hydrologic zones, which allows managers to strategically target restoration and conservation measures, invest funds in habitat likely to have high Journal of Wildlife Management 2022;e22351. wileyonlinelibrary.com/journal/jwmg |
White-nose syndrome (WNS) has emerged as the most serious threat to North American cave-dwelling bat species, with estimated mortality of over 6 million. Tri-colored bat Perimyotis subflavus is one of the species most affected, with hibernaculum counts at caves in WNS-positive regions reduced by >90% from previous counts. While declines have been documented in hibernaculum surveys, long-term monitoring programs during active seasons provide a unique opportunity to examine population trends and impact of population declines post-WNS. We developed generalized linear mixed models using data from a state-wide, long-term (2011–2020) mobile bat acoustic monitoring program in Georgia, USA, to better understand P. subflavus population trends before and after disease detection and between WNS-negative and WNS-positive regions. We recorded 5046 P. subflavus passes across all acoustic routes during the 10-year time period. We detected a significant decrease in activity 2 years after disease detection in the WNS-positive region, whereas activity in the WNS-negative region remained stable over time. Understanding changes in bat populations as WNS spreads and measuring the magnitude of population declines to assess disease impacts is crucial for providing appropriate guidance for management. Our results provide evidence of the critical status of P. subflavus in the southernmost WNS-positive region, but also emphasize the importance of monitoring WNS spread to new regions which could provide refugia for the species and a potential source of recolonization to WNS-affected areas.
White-nose syndrome (WNS) is a disease caused by the fungus Pseudogymnoascus destructans which has resulted in the deaths of millions of bats across eastern North America. To date, hibernacula counts have been the predominant means of tracking the spread and impact of this disease on bat populations. However, an understanding of the impacts of WNS on demographic parameters outside the winter season is critical to conservation and recovery of bat populations impacted by this disease. We used long-term monitoring data to examine WNS-related impacts to summer populations in West Virginia, where WNS has been documented since 2009. Using capture data from 290 mist-net sites surveyed from 2003 to 2019 on the Monongahela National Forest, we estimated temporal patterns in presence and relative abundance for each bat species. For species that exhibited a population-level response to WNS, we investigated post-WNS changes in adult female reproductive state and body mass. Myotis lucifugus (little brown bat), M. septentrionalis (northern long-eared bat), and Perimyotis subflavus (tri-colored bat) all showed significant decreases in presence and relative abundance during and following the introduction of WNS, while Eptesicus fuscus (big brown bat) and Lasiurus borealis (eastern red bat) responded positively during the WNS invasion. Probability of being reproductively active was not significantly different for any species, though a shift to earlier reproduction was estimated for E. fuscus and M. septentrionalis. For some species, body mass appeared to be influenced by the WNS invasion, but the response differed by species and reproductive state. Results suggest that continued long-term monitoring studies, additional research into impacts of this disease on the fitness of WNS survivors, and a focus on providing optimal non-wintering habitat may be valuable strategies for assessing and promoting recovery of WNS-affected bat populations.
Tricolored bats (Perimyotis subflavus) that roost in subterranean hibernacula have experienced precipitous declines from white-nose syndrome (WNS); however, understudied populations also use during winter non-subterranean roosts such as tree cavities, bridges, and foliage. Our objectives were to determine winter roost use by tricolored bats in an area devoid of subterranean roosts, determine roost microclimates to relate them to growth requirements of the fungal causal agent of WNS, and determine habitat factors influencing winter tree selection. From November to March 2017–2019, we used radiotelemetry to track 15 bats to their day roosts in the upper Coastal Plain of South Carolina and recorded microclimates in accessible tree cavities and bridges. We also characterized habitat and tree characteristics of 24 used trees and 153 random, available trees and used discrete choice models to determine selection. Roost structures included I-beam bridges, cavities in live trees, and foliage. Bridges were warmer and less humid than cavities. Roost temperatures often were amenable to fungal growth (< 19.5°C) but fluctuated widely depending on ambient temperatures. Bats used bridges on colder days (8.7°C ± 5.0 SD) and trees on warmer days (11.3°C ± 5.4). Bats selected low-decay trees closer to streams in areas with high canopy closure and cavity abundance. Bats also appeared to favor hardwood forests and avoid pine forests. Our results suggest that access to multiple roost microclimates might be important for tricolored bats during winter, and forest management practices that retain live trees near streams and foster cavity formation in hardwood forests likely will benefit this species. Our results also suggest tricolored bats using bridge and tree roosts might be less susceptible to WNS than bats using subterranean hibernaculum roosts. Thus, forests in areas without subterranean hibernacula in the southeastern United States that support bats during winter might represent important refugia from WNS for multiple species.
We studied roosting ecology of a group of Indiana bats (Myotis sodalis) in southern Michigan over 4 years. Thirty-seven of 38 roost trees used by adult females and young were located in wetlands, and 36 were elms (Ulmus spp.), ashes (Fraxinus spp.) or maples (Acer spp.). Roost trees had larger diameters than randomly selected trees, and roosting areas typically received more than 10 h of sunlight each day. Bats changed trees every 2-3 days, and new roost trees likely were discovered as bats foraged or commuted between foraging areas. Pregnant females switched more often than lactating adults, and bats roosting in crevices changed less often than when the same bats roosted under bark. Maximum distance moved between trees overnight was 5.8 km, but maximum distance between any two roosts discovered over 4 years was 9.2 km. The focal point of roosting activity moved 2 km across the landscape over 3 years. Frequent roost-switching, large home ranges, and changes in activity center between years create challenges for detection, monitoring, and management of this endangered species.
Assessing the scope and severity of threats is necessary for evaluating impacts on populations to inform conservation planning. Quantitative threat assessment often requires monitoring programs that provide reliable data over relevant spatial and temporal scales, yet such programs can be difficult to justify until there is an apparent stressor. Leveraging efforts of wildlife management agencies to record winter counts of hibernating bats, we collated data for 5 species from over 200 sites across 27 U.S. states and 2 Canadian provinces from 1995 to 2018 to determine the impact of white‐nose syndrome (WNS), a deadly disease of hibernating bats. We estimated declines of winter counts of bat colonies at sites where the invasive fungus that causes WNS (Pseudogymnoascus destructans) had been detected to assess the threat impact of WNS. Three species undergoing species status assessment by the U.S. Fish and Wildlife Service (Myotis septentrionalis, Myotis lucifugus, and Perimyotis subflavus) declined by more than 90%, which warrants classifying the severity of the WNS threat as extreme based on criteria used by NatureServe. The scope of the WNS threat as defined by NatureServe criteria was large (36% of Myotis lucifugus range) to pervasive (79% of Myotis septentrionalis range) for these species. Declines for 2 other species (Myotis sodalis and Eptesicus fuscus) were less severe but still qualified as moderate to serious based on NatureServe criteria. Data‐sharing across jurisdictions provided a comprehensive evaluation of scope and severity of the threat of WNS and indicated regional differences that can inform response efforts at international, national, and state or provincial jurisdictions. We assessed the threat impact of an emerging infectious disease by uniting monitoring efforts across jurisdictional boundaries and demonstrated the importance of coordinated monitoring programs, such as the North American Bat Monitoring Program (NABat), for data‐driven conservation assessments and planning.
In multihost disease systems, differences in mortality between species may reflect variation in host physiology, morphology, and behavior. In systems where the pathogen can persist in the environment, microclimate conditions, and the adaptation of the host to these conditions, may also impact mortality. White‐nose syndrome (WNS) is an emerging disease of hibernating bats caused by an environmentally persistent fungus, Pseudogymnoascus destructans. We assessed the effects of body mass, torpid metabolic rate, evaporative water loss, and hibernaculum temperature and water vapor deficit on predicted overwinter survival of bats infected by P. destructans. We used a hibernation energetics model in an individual‐based model framework to predict the probability of survival of nine bat species at eight sampling sites across North America. The model predicts time until fat exhaustion as a function of species‐specific host characteristics, hibernaculum microclimate, and fungal growth. We fit a linear model to determine relationships with each variable and predicted survival and semipartial correlation coefficients to determine the major drivers in variation in bat survival. We found host body mass and hibernaculum water vapor deficit explained over half of the variation in survival with WNS across species. As previous work on the interplay between host and pathogen physiology and the environment has focused on species with narrow microclimate preferences, our view on this relationship is limited. Our results highlight some key predictors of interspecific survival among western bat species and provide a framework to assess impacts of WNS as the fungus continues to spread into western North America.
White-nose syndrome (WNS) has caused large declines in bat populations across eastern North America, making information on demographics of affected species critical to determining their risk for extinction. We used Cormack–Jolly–Seber models to estimate apparent survival rates of hibernating tricolored bats (Perimyotis subflavus) for 5 years in four small abandoned mines in the Ouachita Mountains of Arkansas, located within the WNS endemic area of the United States. Populations in individual mines varied greatly in survival rates, with one mine displaying annual survival rates as high as 0.706 and another as low as 0.101. Differences in survival among bats in different mines could not definitively be attributed to WNS, but may have varied based on a combination of WNS, disturbance, mine climate, and other unknown factors. Further, some hibernacula may have served as temporary winter shelter for young transient males. Sites housing small colonies of hibernating bats may result in high survival rates despite WNS, and protecting these smaller sites may be important for overall species perseverance.
Context
Conservation for the Indiana bat ( Myotis sodalis) , a federally endangered species in the United States of America, is typically focused on local maternity sites; however, the species is a regional migrant, interacting with the environment at multiple spatial scales. Hierarchical levels of management may be necessary, but we have limited knowledge of landscape-level ecology, distribution, and connectivity of suitable areas in complex landscapes.
Objectives
We sought to (1) identify factors influencing M. sodalis maternity colony distribution in a mosaic landscape, (2) map suitable maternity habitat, and (3) quantify connectivity importance of patches to direct conservation action.
Methods
Using 3 decades of occurrence data, we tested a priori , hypothesis-driven habitat suitability models. We mapped suitable areas and quantified connectivity importance of habitat patches with probabilistic habitat availability metrics.
Results
Factors improving landscape-scale suitability included limited agriculture, more forest cover, forest edge, proximity to medium-sized water bodies, lower elevations, and limited urban development. Areas closer to hibernacula and rivers were suitable. Binary maps showed that 30% of the study area was suitable for M. sodalis and 29% was important for connectivity. Most suitable patches were important for intra-patch connectivity and far fewer contributed to inter-patch connectivity.
Conclusions
While simple models may be effective for small, homogenous landscapes, complex models are needed to explain habitat suitability in large, mixed landscapes. Suitability modeling identified factors that made sites attractive as maternity areas. Connectivity analysis improved our understanding of important areas for bats and prioritized areas to target for restoration.
White-nose syndrome (WNS), an epizootic disease caused by an invasive fungus, threatens bat populations across North America. WNS-induced changes in summer bat populations could impact functional diversity. We assessed the shift in relative abundance within an assemblage of bats in a temperate southern Appalachian forest in North Carolina and Tennessee from 2009 through 2016. We used mixed linear effects models to identify bat species significantly impacted by WNS and those showing resistance, and to determine effects on reproductive rates for WNS-affected species. Four once common species — the little brown bat (Myotis lucifugus), Indiana bat (M. sodalis), northern long-eared bat (M. septentrionalis), and tri colored bat (Perimyotis subflavus) — showed significant and dramatic declines (82–99%), while the big brown bat (Eptesicus fuscus), red bat
(Lasiurus borealis), Rafinesque’s big-eared bat (Corynorhinus rafinesquii), and small-footed bat (M. leibii) did not decline significantly after WNS was detected on the landscape. We detected no significant interactions between reproductive condition and WNS period (pre and post-arrival of the disease). Declines in summer populations mirrored declines detected in nearby winter hibernacula. Because the loss of WNS-affected bat species could negatively impact ecosystem health, it is important to monitor bat, insect, and plant community responses wherever WNS threatens bats. We hypothesize that, in the absence of small-bodied bats, there might be increases in populations of small forest pests, such as defoliating moths, as larger WNS-resistant bats may avoid or miss these small prey.
The persistence of populations declining from novel stressors depends, in part, on their ability to respond by trait change via evolution or plasticity. White‐nose syndrome (WNS) has caused rapid declines in several North America bat species by disrupting hibernation behaviour, leading to body fat depletion and starvation. However, some populations of Myotis lucifugus now persist with WNS by unknown mechanisms.
We examined whether persistence of M. lucifigus with WNS could be explained by increased body fat in early winter, which would allow bats to tolerate the increased energetic costs associated with WNS. We also investigated whether bats were escaping infection or resistant to infection as an alternative mechanism explaining persistence.
We measured body fat in early and late winter during initial WNS invasion and 8 years later at six sites where bats are now persisting. We also measured infection prevalence and intensity in persisting populations.
Infection prevalence was not significantly lower than observed in declining populations. However, at two sites, infection loads were lower than observed in declining populations. Body fat in early winter was significantly higher in four of the six persisting populations than during WNS invasion.
Physiological models of energy use indicated that these higher fat stores could reduce WNS mortality by 58%–70%. These results suggest that differences in fat storage and infection dynamics have reduced the impacts of WNS in many populations. Increases in body fat provide a potential mechanism for management intervention to help conserve bat populations.
The tricolored bat (Perimyotis subflavus) is widely distributed throughout eastern North America. However, this species has also undergone severe population declines in areas where white-nose syndrome has taken hold. Previous records in Colorado showed what appeared to be vagrant individuals with no evidence of established populations. Herein we provide new records for Boulder and Weld Counties, Colorado. We also provide evidence of reproduction supporting the hypothesis of westward expansion of this species. Because the tricolored bat has been significantly impacted by white-nose syndrome in eastern North America, the Rocky Mountain West may provide at least a temporary refugium from this disease.
Resumen
Los lineamientos para el uso de especies de mamíferos de vida silvestre en la investigación con base en Sikes et al. (2011) se actualizaron. Dichos lineamientos cubren técnicas y regulaciones profesionales actuales que involucran el uso de mamíferos en la investigación y enseñanza; también incorporan recursos nuevos, resúmenes de procedimientos y requisitos para reportes. Se incluyen detalles acerca de captura, marcaje, manutención en cautiverio y eutanasia de mamíferos de vida silvestre. Se recomienda que los comités institucionales de uso y cuidado animal (cifras en inglés: IACUCs), las agencias reguladoras y los investigadores se adhieran a dichos lineamientos como fuente base de protocolos que involucren mamíferos de vida silvestre, ya sea investigaciones de campo o en cautiverio. Dichos lineamientos fueron preparados y aprobados por la ASM, en consulta con profesionales veterinarios experimentados en investigaciones de vida silvestre y IACUCS, de quienes cuya experiencia colectiva provee un entendimiento amplio y exhaustivo de la biología de mamíferos no-domesticados. La presente versión de los lineamientos y modificaciones posteriores están disponibles en línea en la página web de la ASM, bajo Cuidado Animal y Comité de Uso: (http://mammalogy.org/uploads/committee_files/CurrentGuidelines.pdf). Recursos adicionales relacionados con el uso de animales de vida silvestre para la investigación se encuentran disponibles en (http://www.mammalsociety.org/committees/animal-care-and-use#tab3).
We know little about how forest bats, which are cryptic and mobile, use roosts on a landscape scale. For widely distributed species like the endangered Indiana bat Myotis sodalis, identifying landscape-scale roost habitat associations will be important for managing the species in different regions where it occurs. For example, in the southern Appalachian Mountains, USA, M. sodalis roosts are scattered across a heavily forested landscape, which makes protecting individual roosts impractical during large-scale management activities. We created a predictive spatial model of summer roosting habitat to identify important predictors using the presence-only modeling program MaxEnt and an information theoretic approach for model comparison. Two of 26 candidate models together accounted for >0.93 of AICc weights. Elevation and forest type were top predictors of presence; aspect north/south and distance-to-ridge were also important. The final average best model indicated that 5% of the study area was suitable habitat and 0.5% was optimal. This model matched our field observations that, in the southern Appalachian Mountains, optimal roosting habitat for M. sodalis is near the ridge top in south-facing mixed pine-hardwood forests at elevations from 260-575 m. Our findings, coupled with data from other studies, suggest M. sodalis is flexible in roost habitat selection across different ecoregions with varying topography and land use patterns. We caution that, while mature pine-hardwood forests are important now, specific areas of suitable and optimal habitat will change over time. Combining the information theoretic approach with presence-only models makes it possible to develop landscape-scale habitat suitability maps for forest bats.
Objectives of this 5-year study (1996–2000) were to determine whether Indiana bats (Myotis sodalis) showed short-or long-term fidelity to particular roost trees or areas and to develop broadly applicable definitions for types of fidelity by bats. We radiotracked 60 Indiana bats captured near a hibernaculum in the Daniel Boone National Forest, Pulaski Co., Kentucky, during nine tracking periods (two in early spring, two in summer, and five in autumn). Sixteen bats were tracked in multiple periods. Bats used 280 roost trees of 17 species. Individuals switched trees every 2.21 days but commonly returned to previously used trees, in either a consecutive or nonconsecutive manner. Although there was a positive relationship between number of days tracked and number of trees used by individuals, bats often used particular trees and areas over multiple seasons or years. A kernel home-range analysis identified eight areas of repeated use within 4.75 km of the hibernaculum. Some bats used two or more of these areas, implying that individuals were aware of alternative tracts for use when existing roosts or areas became unsuitable. Biologists must consider various types of fidelity by Indiana bats when developing management plans for areas near hibernacula.
Little information has been published on selection of tree roosts by eastern pipistrelles (Perimyotis subflavus )i n forested environments, and no radiotelemetry-based studies have been conducted on males in forested settings. Therefore, we used radiotelemetry to characterize summer roost selection by 21 male (33 roosts) and 7 female (14 roosts) eastern pipistrelles during 6 years in a forested region of the Ouachita Mountains of Arkansas. All roosts were located in the vegetation of tree canopies; 50% of roosts of females and 91% of roosts of males were in dead leaves of deciduous trees. Three (43%) of 7 maternity colonies were in dead needles of large live pines (Pinus echinata); this is the 1st documented use of pines by this species for roosting. Males selected tree sizes randomly but females selected trees that were larger (P , 0.05) than random. For males, 87% of roosts were in oaks (Quercus), and males roosted at sites with more midstory hardwoods, more large pines in the overstory, less canopy cover, and farther from the nearest trees than random locations. In a landscape offering a diversity of forest habitats, eastern pipistrelles during summer roosted mostly in leaves of oaks in mature (� 50-year-old) forest with a relatively complex structure and a hardwood component.
Forest management affects the quality and availability of roost sites for forest-dwelling bats, but information on roost selection beyond the scale of individual forest stands is limited. We evaluated effects of topography (elevation, slope, and proximity of roads and streams), forest habitat class, and landscape patch configuration on selection of summer diurnal roosts by 6 species of forest-dwelling bats in a diverse forested landscape of the Ouachita Mountains, Arkansas, USA. Our objectives were to identify landscape attributes that potentially affect roost placement, determine whether commonalities exist among species in their response to landscape attributes, and evaluate the effects of scale. We modeled roost selection at 2 spatial scales (250- and 1,000-m radius around each roost). For each species, parameters included in models differed between the 2 scales, and there were no shared parameters for 2 species. Average coefficients of determination (R2) for small-scale models were generally ...
Many studies of roost selection by forest-dwelling bats have concentrated on microhabitat surrounding roosts without providing forest stand-level preferences of bats; thus, those studies have provided only part of the information needed by managers. We evaluated diurnal summer roost selection by the bat community at the forest-stand level in a diversely forested landscape in the Ouachita Mountains of central Arkansas. Over a 6-year period, we evaluated 428 roost locations for 162 individual bats of 6 species. Using Euclidean distance analysis and individual bat as the experimental unit, all 6 species were selective (P < 0.05) in their choice of roosting habitat. Five of six species preferred (P < 0.05) to roost in or near mature (≥50 years old), mixed pine-hardwood forest that had undergone recent partial harvest, midstory removal, and burning; 41.3% of roosts were located in that habitat but it comprised an average of only 22.8% of available habitat. Five of six species also preferred older (≥100 years old), relatively unmanaged, mixed pine-hardwood forest. Although 19.9% of roosts from all species were located in 50- to 99-year-old, second-growth forests of mixed pine-hardwood (average of 21.0% of available habitat), that habitat was preferred by no species of bat. In partially harvested stands, unharvested buffer strips (greenbelts) surrounding ephemeral streams were used at differing levels by each species; most (90%) eastern pipistrelle (Pipistrellus subflavus) roosts were in greenbelts whereas few (2.7%) Seminole bat (Lasiurus seminolus) roosts were in greenbelts. Older forests, thinned mature forests with reduced midstories, and greenbelts retained in harvested areas were all important roosting habitats for the bat community in the Ouachita Mountains. Our results demonstrate the importance of open forest conditions and a diversity of stand types to bat communities of the southeastern U.S.
The practical analysis of space use and habitat selection by animals is often a problem due to the lack of well-designed programs. I present here the “adehabitat” package for the R software, which offers basic GIS (Geographic Information System) functions, methods to analyze radio-tracking data and habitat selection by wildlife, and interfaces with other R packages. These tools can be downloaded freely on the internet. Because the functions of this package can be combined with other functions of R, “adehabitat” provides a powerful environment for the analysis of the space and habitat use.
Although roost sites are critically important to bats, we have few data on macrohabitat factors that affect roost selection by foliage-roosting bats. Such data are needed so that forest managers can make informed decisions regarding conservation of bat roosts. Our objective was to examine roost selection by non-reproductive eastern pipistrelles (Perimyotis subflavus) and red bats (Lasiurus borealis) in a dense deciduous forest undergoing low-intensity timber management in the southern Appalachian Mountains of western North Carolina, USA. During May to August 2004–2006, we radiotracked eight red bats and seven pipistrelles to roosts for 1–14 days (red bats, days, n = 19 roosts; pipistrelles, days, n = 15 roosts). We compared roost and random trees or points using paired-sample t-tests for tree and microhabitat characters and logistic regression models of one to three variables for macrohabitat characters. Neither red bats nor pipistrelles selected roosts based on tree or microhabitat characteristics. Red bats used a wide range of stand ages and conditions and, based on our most plausible models for macrohabitat variables, roosted closer than expected to linear openings such as gated roads. Pipistrelles only used stands ≥72 years in age and roosted closer than expected to non-linear openings and at elevations lower than expected . Combined evidence of multiple variables indicated that pipistrelles preferred to roost close to streams. Our results indicate that land managers in the southern Appalachians should maintain a diversity of age classes to provide roosting habitat for both species, and that pipistrelles in particular may benefit from retention of mature stands or buffer zones near perennial streams. Furthermore, non-reproductive red bats and pipistrelles may prefer to roost near openings to minimize commuting costs when openings comprise a small proportion of a densely forested landscape.
The Indiana bat (Myotis sodalis), a species that is federally endangered in the U.S., is being impacted by white-nose syndrome and habitat loss across much of its range. A better understanding of summer roost ecology of the species will enable us to develop management strategies that promote summer survival for breeding adult females and their pups. We conducted a 5 year investigation of Indiana bat roost habitat selection and roosting behavior in a large (>250,000 ha) forested area of the southern Appalachian Mountains and compared our results to populations in different landscapes across the species’ range. From May to August 2008–2012, we attached radio transmitters to 50 adult females, 3 juveniles, and 7 adult males captured at sites on the Cherokee and Nantahala national forests and Great Smoky Mountains National Park. We radiotracked bats to 95 roosts and measured characteristics of trees, 0.1 ha plots, and landscape attributes for 69 of these roosts and associated random trees. We used an AIC approach to compare 14 candidate conditional logistic regression models. The only plausible model, which carried 95% of total model weights, had 3 important terms. Indiana bats showed strong selection for yellow pine (Pinus subgenus Diploxylon) snags that were significantly taller than random trees and in areas with a greater number of snags within 0.1 ha. During this study, tree and stand structure were more important for roost selection than larger scale factors and Indiana bats responded to a pulsed and highly ephemeral resource, dead yellow pines, which were a significant component of the large forest tracts. Roosting behavior differed from what has been observed for Indiana bats in other parts of the eastern U.S.; maternity colonies tended to be smaller (<25 bats, but as large as 75 bats prior to pups being volant) and bats were more nomadic, using each roost tree for only 2–3 days on average and rarely for more than one year. The differences we observed in roosting behavior in the southern Appalachians suggest it would be wise to consider the broader landscape context when evaluating the roosting ecology of Indiana bats, as local forest types and disturbance events will affect stand structure and roost tree availability. Stand- and landscape-scale management practices that create or preserve large pine snags, such as prescribed fire, coupled with natural or manmade pulsed disturbances, should aid in the management and recovery of the Indiana bat in this region.
Sexual segregation is common in polygynous mammals, particularly in wild ungulates, but is less known in bats of North America. Yet, the declining bat populations caused by white-nose syndrome, wind energy facilities, and habitat loss throughout eastern North America require habitat management, which may be sex specific. We thus determined sex-specific roosting and foraging habits of evening bats (Nycticeius humeralis) in north-central Arkansas. During the summers of 2013 and 2014, we equipped 70 individuals with radiotransmitters to track their foraging movements and identify their roosts that we characterized with 3 tree-level and 7 plot-level variables. We found that evening bat males and females segregate spatially with females foraging over a larger area than males. Females’ roosts were also higher in elevation. Although the roost itself had similar characteristics between sexes, its surrounding habitat was characterized by less canopy cover and a smaller basal area for females. Our results support sex-specific habits and sexual segregation in a forest-dwelling bat, which highlights the importance of sex-specific studies to inform management decisions that would benefit both sexes, including females for which parental investment is higher.
Many land-management agencies are restoring savannas and woodlands using prescribed fire and forest thinning, and information is needed on how wildlife species respond to these management activities. Our objectives were to evaluate support for relationships of bat site occupancy with vegetation structure and management and landscape composition and structure across a gradient of savanna to forest in the Missouri Ozark Highlands, USA. We selected study sites that were actively managed for savanna and woodland conditions and control areas on similar landforms that had succeeded to closed-canopy forest. We used Anabat detectors to survey bats during the summers of 2010, 2011, and 2012. We fit single-species site-occupancy models to estimate detection probability and site occupancy. We evaluated a priori hypotheses in an information theoretic approach by evaluating support for candidate models that included habitat, landscape, and management effects. Site occupancy of evening bats (Nycticeius humeralis) was negatively related to poletimber and sawtimber density and positively related to fire frequency, while northern long-eared bat (Myotis septentrionalis) site occupancy was positively related to poletimber density and negatively related to understory stem densities. Site occupancy of big brown bats (Eptesicus fuscus), eastern red bats (Lasiurus borealis), and tri-colored bats (Perimyotis subflavus) were mostly not related to local vegetation structure and site occupancy was high across the savanna, woodland, forest gradient. We found more consistent and larger effect sizes for landscape-scale than for habitat-scale relationships; therefore, land managers should be cognizant of large-scale patterns in land cover when making local management decisions for these species. Published 2014. This article is a U.S. Government work and is in the public domain in the USA.
As an increasingly dominant feature in the landscape, transportation corridors are becoming a major concern for bats. Although wildlife—vehicle collisions are considered to be a major source of mortality, other negative implications of roads on bat populations are just now being realized. Recent studies have revealed that bats, like many other wildlife species, will avoid roads rather than cross them. The consequence is that roads act as barriers or filters to movement, restricting bats from accessing critical resources. Our objective was to assess specific features along the commuting route, road, or surrounding landscape (alone or in combination) that exacerbated or alleviated the likelihood of a commuting bat exhibiting an avoidance behavior in response to an approaching vehicle. At 5 frequently used commuting routes bisected by roads, we collected data on vehicles travelling along the roads (such as visibility and audibility), commuting bats (such as height), and composition of the commuting route. We revealed that commuting route structure dictated the frequency at which bats turned back along their commuting routes and avoided the road. We found that gaps (>2 m) in commuting routes, such as the road itself, caused bats to turn away just before they reached the road. Furthermore, we found that turning frequencies of bats increased with vehicle noise levels and the locations at which bats responded to vehicles corresponded with areas where noise levels were greatest, including gaps <2 m. This suggested that bats had a disturbance threshold, and only reacted to vehicles when associated noise reached a certain level. We found that threshold levels for our study species were approximately 88 dB, but this value was likely to vary among species. Thus, our findings indicate that restoring (e.g., replanting native trees and shrubs in gaps) and establishing commuting routes (such as planting tree-lines and wooded hedgerows), as well as creating road-crossing opportunities (such as interlinking canopies) will improve the permeability of a road-dominated landscape to bats. Furthermore, our study highlights the influence of the soundscape. We recommend that effective management and mitigation strategies should take into account the ecological design of the acoustic environment.
We studied roosting ecology of reproductive (pregnant or lactating) adult female eastern pipistrelles (Pipistrellus subflavus) in Indiana. Nineteen bats were radiotagged and 37 roost trees identified. Pipistrelles roosted exclusively in foliage, typically in clusters of dead leaves (65%) and less often in live foliage (30%) or squirrel nests (5%). Oaks (Quereus species) were preferred as roost trees. Roost trees and height of foliage roosts were both located well below the forest canopy. Bats remained at roost trees for 6 days on average before moving to new roosts and traveled approximately 19–139 m between roost trees. This is the 1st thorough analysis of roosting habits of this common species under natural conditions.
Une population apparemment isolée de pipistrelles de l'Est (Perimyotis subflavus) existe dans le sud-ouest de la Nouvelle-Écosse. Durant les étés 2003–2004 et 2007–2008, nous avons attrapé des chauves-souris avec des filets japonais sur un pont de la rivière Mersey dans le parc national Kejimkujik. Au total, nous avons capturé 42 pipistrelles de l'Est (41 femelles et 1 mâle) et avons placé un émetteur radio sur 32 femelles et l'unique mâle. Nous les avons suivis quotidiennement jusqu'à leurs sites de repos. Les caractéristiques de ces dortoirs ont été comparées à celles d'autres dortoirs aléatoires potentiellement disponibles en utilisant un ensemble de modèles potentiels sélectionnés a priori et classés grâce à AICc pour la sélection de modèles. Au total, nous avons trouvé 99 arbres dortoirs différents dans 9 aires de repos distinctes (8 femelles, 1 mâle). En moyenne, les chauves-souris passaient 2,5 jours dans un arbre dortoir. Alors que leurs conspécifiques d'autres parties de l'aire de distribution de l'espèce se reposent habituellement dans le feuillage des arbres, les colonies de maternité des pipistrelles de l'Est en Nouvelle-Écosse se reposent exclusivement dans du lichen Usnea trichodea, en général dans des conifères (dont 91 % d'épinettes; Picea spp.) situés en moyenne à 212 m de l'eau. Seulement 4 % de 300 arbres sélectionnés aléatoirement dans l'aire d'étude avaient du lichen Usnea trichodea. Ces arbres comprenaient un mélange de bois tendre et dur (58 % et 42 %, respectivement) et étaient situés en moyenne à 550 m de l'eau. Ces résultats démontrent une relation apparemment unique entre des lichens et des chauves-souris ayant probablement des impacts sur plusieurs aspects de la biologie de l'espèce incluant la distribution, la structure sociale et la prévalence de parasites. Nomenclature: Farrar, 1995; van Zyll de Jong, 1998; Brodo, Sharnoff & Sharnoff, 2001; Sibley, 2003.
Bats in forests have strict roosting habitat requirements. The current paradigm in bat conservation has been to identify the specific characteristics of individual roost trees that are selected by bats. Although this strategy is both practical and useful, it is also important to recognize landscape level interactions between bats and their roost habitats. Few studies have documented fidelity patterns of individual bats to specific roost habitat areas both within and between years. If bats are faithful to roost areas, conservation and management practices must incorporate the identification of the minimum size of areas required by bats during the summer season. We provide evidence that female eastern pipistrelles are faithful to small roost areas both within and between years, and that juvenile females exhibit female natal philopatry.
We describe the size and developmental state at birth, examine factors which influence intra- and inter-year variation in post-natal growth, and derive age-predictive equations and logistic growth parameters for the eastern pipistrelle bat, Pipistrellus subflavus. Ambient and roost temperature and insect abundance were lowest, and precipitation highest, before and during the post-natal growth period in 1982, as compared to 1981. We found no sex differences in the size of pups at birth or in post-natal growth rates in a given year; however, body mass and length of forearm of neonates differed significantly between years, being smaller in 1982 than in 1981. During the first two weeks of post-natal growth in both years, the body mass and length of forearm of pups increased linearly at mean rates of 0.15 g.day−1 and 1.12 mm.day−1, respectively. Post-natal growth rates for length of forearm and body mass were the same during the early linear phase of growth, but the intercept for body mass was less and growth trajectories were more variable in 1982. Length of forearm was the least variable and thus most reliable character for estimating age of P. subflavus pups during the first 14 days of post-natal growth. When length of forearm was used in combination with mean changes in the length of the fourth metacarpal-phalangeal epiphyseal gap, we derived reliable age-estimation equations ranging from 1 to 45 days. Litter size averaged 1.96 and 1.93 at birth, but this was reduced to one by the time pups became volant. At birth, litter mass represented 44, and 54% of the post-partum mass of females in 1981 and 1982, respectively. This maternal effort during pregnancy is among the highest reported for bats. At weaning, the body mass of pups approached 80% of adult post-partum body mass, and the length of forearm exceeded 90% of adult female size. Our results suggest that size at birth and post-natal growth are influenced by ambient and roost temperature, rainfall, and the quantity of insects available to pregnant and lactating females. Thus, energetic constraints on both mothers and pups can lead to inter-year and inter-individual differences in maternal effort and post-natal growth of pups.
Early successional habitats are important foraging and commuting sites for the 14 species of bats that inhabit the Central
Hardwood Region, especially larger open-adapted species such as hoary bats (Lasiurus cinereus), red bats (L. borealis), silver-haired bats (Lasionycteris noctivagans), and big brown bats (Eptesicus fuscus). Forest gaps, small openings, and the edges between early successional patches and mature forest are especially important
habitats because they are used by both open-adapted and clutter-adapted species. Several bat species select roosts in close
proximity to early successional patches, perhaps to minimize foraging and commuting costs. Future research on effects of early
successional patch size, shape, vegetation structure, and connectivity on bat use, and the distribution of early successional
habitats in relation to mature forest, roosting sites, and water sources will assist managers in providing the optimal types
and distribution of early successional patches on the landscape.
Declining bat populations and increasing demands on forest resources have prompted researchers to investigate tree roost selection of forest bats. Few studies, however, have investigated different spatial scales and landscape pattern as criteria for selection of tree roosts. In 1999 and 2000, we radiotracked 23 eastern red bats (Lasiurus borealis) to 64 day roosts. Using univariate and multivariate comparisons, we tested roost tree variables with random tree data at 3 circular spatial scales: roost tree, plot, and landscape. We found 15 variables that were entered in a stepwise discriminant analysis to best differentiate between the roost and random samples; 11 (73.3%) were landscape variables measured with a geographic information system. On average (x +/- SE), red bats roosted in deciduous trees (42.0 +/- 2.1 cm dbh) that were located in plots with more (3.1 +/- 0.1 m(2)) basal area, higher (84.0 +/- 1.3) percentage of canopy closure, and lower (27.2 +/- 2.2) percentage of groundcover than random plots. At the landscape scale (by percent magnitude), red bat buffers (1,000-m-radius circle) had significantly less development (81.6%), less feeding operations (70.4%), more deciduous (52.9%) and pine forest (63.8%), and fewer local roads (5.4%) but more trails (94.1%), open water (61.4%), wetland areas (80.4%), and stream areas (63.1%) than random buffers. Red bat roost trees were significantly closer (chi(2) = 22.0088, df = 1, P <= 0.001) to trails (106.2 +/- 13.3 m) than to streams (279.4 +/- 28.5 m). Our results suggest that red bats in our study area select roosts in mature riparian forests near trails, open water, and wetlands. The high percentage of landscape values in the discriminant analysis lends support to using landscape metrics as an investigative technique of resource selection. We recommend that managers consider landscape factors when protecting red bat day-roost habitat.
In this paper kernel methods for the nonparametric estimation of the utilization distribution from a random sample of locational observations made on an animal in its home range are described. They are of flexible form, thus can be used where simple parametric models are found to be inappropriate or difficult to specify. Two examples are given to illustrate the fixed and adaptive kernel approaches in data analysis and to compare the methods. Various choices for the smoothing parameter used in kernel methods are discussed. Since kernel methods give alternative approaches to the Anderson (1982) Fourier transform methods, some comparisons are made.
Wastewater treatment plant (WWTP) effluent in the Cape Fear River Basin headwaters in North Carolina, USA, has influenced stream water quality and aquatic components of the stream food web. To examine effects of WWTP effluent on terrestrial predators in this system we determined prey availability, bat community structure, and bat foraging and commuting behavior at sites above and below WWTPs. We predicted an effect of effluent in the riparian habitat specialist Perimyotis subflavus but not the habitat generalists Eptesicus fuscus, Lasiurus borealis, or Nycticeius humeralis. Nocturnal insect abundance was higher upstream of the WWTPs. There were more Diptera, Coleoptera, and Lepidoptera upstream of the WWTPs whereas there were more Odonata downstream of the WWTPs. There were more E. fuscus upstream of the WWTPs and more P. subflavus downstream of the WWTPs. Despite the difference in bat community structure up-and downstream of the WWTPs, bat commuting and foraging activity levels were the same; there was no difference in the total number of echolocation sequences we recorded per night up- and downstream of the WWTPs nor was there a difference in the proportion of those sequences that contained a feeding buzz. Our results suggest the effect of anthropogenic nutrients in the stream persists through higher food web trophic levels as we found impacts on nocturnal flying insects as well as two common species of insectivorous bats. Perimyotis subflavus and E. fuscus may serve as easily tractable terrestrial bioindicators of water quality as influenced by WWTP effluent in this, and other, urban watersheds.
Roost fidelity in Kentucky
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Notes on the Pipistrellus subflavus (F. Cuvier) during the season of parturition
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