Bat Occupancy Research Articles

BATS: Bat‐aggregated time series—A python‐based toolkit for landscape‐level monitoring of free‐tailed bats via weather radar

Abstract The US operates a system of 160 S‐band Doppler weather radars known as NEXRAD (NEXt generation weather RADar) that continuously monitors the airspace around the majority of the United States and outlying territories. These radars detect and track birds, insects, and bats. Free‐tailed bats (Genus Tadarida) provide considerable ecosystem services through their voracious insect consumption; but their movements and ecosystem service provision have historically been difficult to track/study in space and time. We introduce ‘BATS’, a Python toolkit that streamlines the process of downloading, classifying, and aggregating time series of free‐tailed bats across large landscapes. BATS retrieves data from NOAA's weather radar data repositories and classifies the processed radar data using a pre‐trained ML trained to detect and classify radar echoes associated with free‐tailed bats. We trained various machine learning approaches at classifying pixels containing free‐tailed bats and compared the effectiveness across approaches. With an AUC of 0.963, the neural network approach is highly effective in identifying free‐tailed bats in NEXRAD data over our study sites in California and Texas. Furthermore, BATS is capable of quickly distilling 6 months of radar data from a single tower (3.5 Tb) into a single 15 Mb‐sized map of bat occurrence, contingent on available computing resources. BATS will help scientists and stakeholders identify areas of high bat occupancy at the landscape level over long periods of time. This ability has the potential to increase our understanding of the economic and agricultural value of these species.

Is it only the hood, or also the neighbour? Bat occupancy and community drivers in heterogeneous urban landscapes

Is it only the hood, or also the neighbour? Bat occupancy and community drivers in heterogeneous urban landscapes

Cave-roosting specialisation of an oceanic island endemic microbat elevates extinction risks as caves face multiple threats

Bats (Chiroptera) constitute one-fifth of the global mammalian diversity, with over 1,450 species. Yet, 16.5 % of them are threatened with extinction, a situation exacerbated on islands, underscoring an urgent need for conservation efforts there. However, effective conservation action can only be as sound as the understanding of the basic ecology of such insular species. Mauritius harbours one endemic Endangered cave-roosting insectivorous bat, in recent decline, whose ecology is poorly known, hampering its conservation. We used Mormopterus acetabulosus as a model species to inform insectivorous island bat conservation in highly transformed habitats. We compared the species’ historical and current known roost distribution and sizes and estimated any change in its Area of Occupancy (AOO) and Extent of Occurrence (EOO) using GeoCAT. We also compiled the physical characteristics, environmental and anthropogenic variables of caves that are occupied and unoccupied by the bats to identify potential factors influencing roost occupancy. We found roosts in 17 of the recorded 130 lava cave tunnels, up from the nine previously recorded, including 11 permanent and six seasonal roosts, mostly (∼71 %) on privately owned land. Compared to the last surveys in 2017, the EOO remained stable at 818.9 km2, while the AOO increased by 33.3 %. This expansion may reflect previously undetected roosts or recent colonisation events or both. Cave dimensions in terms of entrance size and height as well as the number of chambers, relative humidity and distance to water best explained roost occupancy by M. acetabulosus. Caves with larger entrances may be preferred for roosting as this characteristic eases manoeuvrability and predator avoidance, and larger caves may be preferred for enhanced microclimatic stability. Occupied and unoccupied caves were found to differ in terms of physical characteristics, although cave microclimate did not vary notably. Based on their characteristics and their potential contributions to increasing the species’ EOO and AOO, six currently unoccupied caves were identified as priority sites for future conservation efforts. Legal protection of all caves, regardless of current bat occupancy is necessary to mitigate extinction risks and preserve their associated ecological functions.

Distribution and Habitat Selection of Indian Flying Fox, Pteropus medius (Temminck, 1825) in Uttar Pradesh, India

The present study examines the distribution and habitat selection of Indian flying fox, Pteropus medius in Uttar Pradesh, India. A through field work conducted across six districts revealed 22 roosting locations with a total population of approximately 12,023 bats. These sites were located at rural (12), semi-urban (2), urban (1), agricultural (5), and industrial (2) areas, and a majority of roost sites observed close to human habitations. Pteropus medius preferred to roost on 20 species of trees which indicate wide-ranging habitat preferences. Although there were considerable differences in tree attributes across different species, such as tree height (ranging from 9.54 to 26.03 meters), canopy width (varying from 8.59 to 25.09 meters), crown height (ranging from 1.19 to 18.90 meters), circumference (ranging from 0.54 to 3.65 meters), and DBH (ranging from 0.17 to 3.73 meters), and there was no notable variation in bat occupancy per roost tree. The results of the regression analysis emphasized the significance of canopy width as a predictor of colony size, indicating its importance in identifying suitable roosting habitats for P. medius. ANOVA analysis indicated differences in tree characteristics across species, highlighting the necessity for through habitat evaluations. Subsequent post-hoc examination clarified distinct clusters of tree species with significant variations in roosting site features. These results underscore the intricate relationship between tree attributes and bat populations, emphasizing the significance of well-informed conservation approaches for the sustainable preservation of P. medius and the overall ecosystem well-being.

Trade‐offs in habitat use and occupancy of bats across the gradient of urbanization and seasons

AbstractUrbanization that occurs across a gradient from low‐ to high‐density development, is a primary driver of landscape change that can affect biodiversity. Animals balance trade‐offs in obtaining resources and avoiding anthropogenic disturbances across the gradient of urbanization to maximize their fitness. However, additional research is necessary to understand seasonal variations in how animals respond to urbanization, particularly in arid regions, where resource availability shifts drastically across seasons. Our objective was to evaluate the response of a suite of bat species to urbanization and whether species shift their response to urbanization across seasons. We predicted that the response of bats to urbanization would differ among species, with some species being more sensitive to urbanization than others. We also predicted that bat species would increase the use of moderate and highly urbanized areas in the summer season where food and water resources were assumed to be greater compared with wildland areas. To evaluate these predictions, we used a stratified random sampling design to sample 50 sites with stationary acoustic bat monitors across the gradient of urbanization in the Phoenix metropolitan area, Arizona, USA during four seasons. We identified a total of 14 bat species during 1000 survey nights. Consistent with predictions, bat species exhibited different responses to urbanization, with most species exhibiting a negative relationship with urbanization, and some species exhibiting a quadratic or positive relationship with urbanization. Counter to predictions, most species did not appear to shift their response to urbanization across seasons. Consistent with predictions, plant productivity and water were important for some species in the summer season. Differences in the response of bat species to urbanization was likely related to species traits (e.g., wing morphology and echolocation call characteristics) and behavioral strategies that influence a species' sensitivity to anthropogenic disturbances and ability to access available resources in urbanized areas. Ultimately, to promote the management and conservation of bats, it is likely important to maintain resources in urbanized areas for bats that are more tolerant of urbanization and to conserve areas of undeveloped high‐quality habitat with low anthropogenic disturbance in wildland areas for bats that are sensitive to urbanization.

Bat winter foraging habitat use in working forests: a multispecies spatial occupancy approach

AbstractInsectivorous bats in temperate zones have evolved strategies such as migration or hibernation to overcome challenges of reduced resource availability and increased energy demand during winter. In the southeastern United States Coastal Plain, bats are either year‐round residents and remain active during winter or are migrants from colder areas seeking milder temperatures. Southeastern Coastal Plain forests also may represent important areas for remnant populations of species impacted by white‐nose syndrome. Working pine (Pinus spp.) forests comprise a large proportion of southeastern Coastal Plain forests, yet winter bat habitat associations and how forest management affects bat use remain understudied. Hence, we used hierarchical multispecies spatial occupancy models to evaluate factors influencing winter bat occupancy and foraging habitat associations in working forests of the southeastern Coastal Plain. From January to March 2020–2022, we deployed Anabat Swift acoustic detectors and measured site‐ and landscape‐level covariates on six working landscapes. We detected five species of bats and three species groups at 93% (224/240) of sites. We observed higher species richness at sites with high proportions of contiguous forest and low levels of basal area. At the species level, occupancy patterns were influenced by site and landscape covariates, which had varying effects on species with distinct foraging strategies. Temperature was an important predictor of detectability. Our findings offer new insights into the ecology of bats in working forest landscapes during winter, where we highlight positive responses in occupancy with contiguous forests and lower levels of basal area, as in previous summer work. By providing valuable information on winter community composition and foraging habitat associations, we hope to guide management decisions for forest attributes important to these species, thus increasing conservation opportunities within working forests.

Patterns of Florida Bonneted Bat Occupancy at the Northern Extent of Its Range

Abstract The Florida bonneted bat Eumops floridanus is a rare, endemic bat of South Florida that roosts in woodpecker cavities and anthropogenic structures such as roofing tiles, chimneys, and bat houses. The northernmost occurrences of the bonneted bat are from mature pine forests at the Avon Park Air Force Range, Florida. We used ultrasonic acoustic recorders to understand bonneted bat activity and habitat occupancy. We modeled occupancy using a hierarchical Bayesian analysis and included site- and time-specific covariates of detection probability and site-specific covariates of occupancy. Probability of detection was low throughout Avon Park Air Force Range but increased with Julian date. In most habitats, occupancy was poorly estimated, except for flatwood mature pinelands where occupancy was low (0.23 ± 0.06). As distance from red-cockaded woodpecker colonies increased, occupancy decreased (β = −1.19 ± 0.26 SD). At the northernmost extent of the range, and throughout much of the historic range, increasing the expanse of mature, fire-maintained forest systems will increase habitat for the bonneted bat and lead to faster population recovery.

Factors affecting bat occupancy of boxes in managed coniferous forests

The gradual conversion of forest stands to single-aged and single-species stands is resulting in the loss of natural roosts for many animal groups. The installation of bat boxes is one solution to compensate for the lack of natural roosting opportunities. The box models differ in their design and material, which to some extent can determine their suitability for bats. We investigated the occupancy of 187 boxes made of wood, ceramic and two sizes concrete with styrofoam; and the intra-seasonal (spring migration, breeding, mating/migration) thermal profile for each type of box. The environment of the boxes was defined by parameters that could directly affect the box’s thermal conditions (solar energy availability), or be related to sociality (distances, obstacles) or food availability (edge of forest, water). The box occupancy depended on the box type and the season: styrofoam-concrete boxes were preferred, with a higher occupancy during the mating and migration period (>75%), whereas the highest species richness occurred in ceramic boxes. Box types also differed significantly in their diurnal thermal profiles: the wooden boxes had inside temperatures similar to outside the box, whereas the styrofoam-concrete and with expanded clay aggregate (ceramic type) averaged 2°C higher. Overall, we found 6 bat species, although we concentrated our analysis on the most common species: Pipistrellus nathusii (88%). For this species, none of the parameters that could affect the box thermal condition had an impact on the occupancy, whereas the presence of obstacles and the distance to a water body, proved to be important. To ascertain that our results may be valid and be the result of differences in the box thermal properties, we tested the relationship of the box occupancy to the latitude, using data available in the literature. The occupancy of wooden boxes from the latter dataset significantly decreases with latitude, whereas for the concrete (with addition of sawdust or styrofoam) it increases, although this relationship is not significant and requires a larger sample.

Bioclimatic Envelopes for Two Bat Species from a Tropical Island: Insights on Current and Future Distribution from Ecological Niche Modeling

Bats perform critical ecosystem functions, including the pollination, seed dispersal, and regulation of invertebrate populations. Yet, bat populations are declining worldwide primarily due to habitat loss and other anthropogenic stressors. Thus, studies on bat ecology, particularly on environmental determinants of bat occupancy, are paramount to their conservation. High mobility, nocturnal behavior, and roosting site selection of bats make conventional surveys challenging. Moreover, little is known about geographic distribution, habitat suitability, and responses to climate change among tropical bat species. To bridge these research gaps, we applied ecological niche modeling to two Ceylonese bat species, Kerivoula malpasi and Kerivoula picta, to map their geographic distribution. Seasonal variations in temperature and precipitation were critical environmental predictors of bat distribution in general. Southwestern lowland forests contained the most optimal habitats for the relatively wide-ranging Kerivoula picta, while the central highlands provided the most suitable habitats for the narrow-ranging Kerivoula malpasi. No tangible changes in the highly suitable habitats were evident in response to projected climate change for either species. Yet, the optimal ranges of K. malpasi can become fragmented in the future, whereas the most optimal habitats for K. picta are likely to become spatially contiguous in the future. Habitat availability or fundamental niche alone is insufficient to reliably forecast species persistence, thus we caution against considering these two bat species as resilient to climate change. Our findings will enable the conservation authorities to initiate preemptive conservation strategies, such as the establishment of landscape-scale habitat connectivity and management of buffer zones around conservation lands. We also encourage conservation authorities to employ ecological niche models to map potential species distributions and to forecast range shifts due to climate change.

Informing wind energy development: Land cover and topography predict occupancy for Arizona bats.

Wind energy is a growing source of renewable energy with a 3-fold increase in use globally over the last decade. However, wind turbines cause bat mortality, especially for migratory species. The southwest United States has high bat species diversity and is an important area for migratory species, although little is known about their seasonal distribution. To examine potential risk to bats in areas proposed for wind energy development, we characterized bat occupancy spatially and temporally across northern Arizona, identifying use during summer when bats are reproductively active and fall during the migratory season. Our objectives were to determine occupancy of migratory species and species of greatest conservation need and develop a probability of occupancy map for species to identify areas of potential conflict with wind energy development. We selected 92 sites in 10 clusters with potential for development and used acoustic detectors to sample bats in the summer and fall of 2016 and 2017 for 6 nights per site per year. We predicted response of migratory bat species and species of special concern to 9 landscape variables using Program MARK. During summer, higher densities of forest on the landscape resulted in a higher probability of occupancy of migratory species such as hoary bats (Lasiurus cinereus), silver-haired bats (Lasionycteris noctivagans), big free-tailed bats (Nyctinomops macrotis), and species of conservation need such as spotted bats (Euderma maculatum). During the fall, higher concentration of valleys on the landscape predicted occupancy of hoary bats, big free-tailed bats, and spotted bats. High bat occupancy in the fall was also associated with higher elevation and close proximity to forests. We recommend that wind turbines be placed in open, flat grasslands away from forested landscapes and concentrations of valleys or other topographic variation.

Monitoring Occupancy of Bats with Acoustic Data: Power and Sample Size Recommendations

Bats are difficult to study due to their nocturnal, cryptic, and highly vagile nature. Ongoing advances in acoustic recording hardware and call classification software have made species detection and activity monitoring more feasible. Our objectives were to determine the effort necessary to monitor bat assemblages using an occupancy framework and acoustic data and to provide guidelines for researchers interested in developing similar monitoring programs. We collected data at 2 study areas in South Texas from June through September in 2015, 2016, and 2017. We used Pettersson D500X Mk II real-time full-spectrum detectors and classified sound files using SonoBat bat call analysis software. We attempted to collect data during 2 visits to individual sites, with up to 5 consecutive nights per visit each year. We estimated occupancy rates for each species in each study area using occupancy models in Program MARK and included terms to define trends in detection probability through the season. Over the 3 years of our study, we sampled 106 sites with 803 sampling nights and classified a total of 2880 sound files to 7 species. Data sets for 6 of the species supported models indicating that detection probability varied throughout our sampling period. Our results generally indicate that sample sizes between 10 and 20 sites would be required to detect declines in occupancy of 50% over 25 years using 10 nights per site with a starting occupancy rate of 0.70. Detecting declines of 30% in 10 years may require >75 sampling sites. Finally, our analysis shows that recognizing seasonal variation in detection probability, and then timing surveys accordingly, can greatly reduce sample size requirements.

Carios kelleyi (Acari: Ixodida: Argasidae) Infected With Rickettsial Agents Documented Infesting Housing in Kansas, United States.

During September-December 2018, 25 live ticks were collected on-post at Fort Leavenworth, Kansas, in a home with a history of bat occupancy. Nine ticks were sent to the Army Public Health Center Tick-Borne Disease Laboratory and were identified as Carios kelleyi (Cooley and Kohls, 1941), a species that seldom bites humans but that may search for other sources of blood meals, including humans, when bats are removed from human dwellings. The ticks were tested for numerous agents of human disease. Rickettsia lusitaniae was identified by multilocus sequence typing to be present in two ticks, marking the first detection of this Rickettsia agent in the United States and in this species of tick. Two other Rickettsia spp. were also detected, including an endosymbiont previously associated with C. kelleyi and a possible novel Rickettsia species. The potential roles of C. kelleyi and bats in peridomestic Rickettsia transmission cycles warrant further investigation.

Insectivorous bat occupancy is mediated by drought and agricultural land use in a highly modified ecoregion

AbstractAimCalifornia's Central Valley, one of the most productive agricultural regions worldwide, is home to a high number of at‐risk species due to habitat conversion. Amplifying the issue, the Central Valley faces severe droughts, creating water scarcity in surrounding natural areas. At least 14 insectivorous bat species live in this region, and prior studies show mixed results regarding the impact of agriculture and drought on bats. The aim of this study was to investigate how bats use agricultural areas during drought.LocationCentral Valley, California, United States.MethodsWe deployed ultrasonic acoustic detectors at 274 sites from March through July of 2016, the final year of an extreme drought, and 2017, one of the wettest years on record. We identified bats to species, used single‐species occupancy models including biologically relevant covariates and created spatial projections of ecoregion‐wide occupancy for each species.ResultsWe modelled occupancy for eight bat species. Long‐distance migrants in the study area contracted their geographic range during the drought, while resident species did not. Five of the eight bats in this analysis were more likely to occupy areas with orchard crop cover. Lastly, arid‐adapted bats used cultivated landscapes during the drought but retracted their range after the drought ended.Main conclusionsMigratory bats appeared to shift occupancy more during drought than resident bats, possibly because of lower roost fidelity. Additionally, the effects of drought on some bat species in the Central Valley may be buffered by agricultural landscapes acting as drought refugia. Overall, this study demonstrates the benefits of broad‐scale acoustic studies which can serve as a tool to track changing bat distributions on the landscape and provide baseline occupancy for acoustically detectable species.

Urban bat occupancy is highly influenced by noise and the location of water: Considerations for nature-based urban planning

Nature-based green infrastructure projects have become a common consideration in cities for the benefits they provide to humans. However, the co-benefits provided to wildlife are often assumed but not critically assessed. The value of green infrastructure for wildlife likely depends on the habitat requirements of a species and the spatial context of that habitat within the landscape. We examined the influence of both natural characteristics and those of the built environment, including noise, on bat species distribution in the Chicago, Illinois metropolitan area. Occupancy rates for four of the eight species in our study responded positively to the proximity of water sources, and three species responded negatively to increasing urban noise. When noise and water were examined in association with one another, the benefits of being adjacent to water quickly diminished as noise levels increased. These results illustrate the importance of considering both natural elements and the built environment in urban habitat design. Our findings demonstrate that cities - when carefully planned and designed - can provide important habitat for bats, a taxa of high conservation need.

Bat Occupancy Based on Mist-Netting Surveys in a Montane Landscape in Northern Andes

Occupancy models have not been commonly used in studies focused on bat ecology, although they offer an opportunity to include site covariates along environmental gradients as well as factors that influence detection probability (e.g., lunar illumination). Here we assessed the influence of elevation and forest cover on occupancy and the effect of lunar illumination on detectability of bat species in the Northern Andes of Peru. We captured 1,052 bats, belonging to three families and 26 species, over two survey periods (2008–2010 and 2014–2015) at 14 sites. The most detected species were the frugivorous Artibeus glaucus, Carollia brevicauda, C. perspicillata, Platyrrhinus ismaeli, P. nigellus, Sturnira erythromos, and S. oporaphilum. Detection probability (p) of both Artibeus planirostris, C. brevicauda and C. perspicillata were significantly related to the survey period, while S. erythromos and S. oporaphilum detectability was associated with lunar illumination. Elevation was marginally positively associated with S. erythromos occupancy, with a moderate relative explanatory power based on AICc weight. We did not find support for an effect of forest cover on bat occupancy. The estimation of both bat occupancy (Ψ) and detectability (p) provides the basis for the design of monitoring programs with a spatiotemporal approach and constitutes a critical component in the context of land-use change and changing climate. For bat species in montane habitats, we suggest that S. erythromos is a useful species for use in monitoring programs, based on both occupancy, and detection probability, as well as its adaptability to montane areas.

Landscape monitoring reveals initial trends in occupancy and activity of bats in multiple‐use forests

AbstractBiodiversity monitoring is recognised as a key action for ecologically sustainable land use, but there are few examples of landscape programmes. We outline the first five years of biodiversity monitoring focusing on insectivorous bats in low rainfall, multiple‐use forests and woodlands of the Pilliga, Australia. Using ultrasonic sampling over multiple nights, both on‐ and off‐tracks, we identify annual trends in bat activity and occupancy and environmental covariates. Trends differed depending on whether occupancy or bat activity was the response variable. Site occupancy was almost 100% and remained stable and/or did not decline for most species nor diversity over the monitoring period, suggesting little variation in bat populations. In comparison, total activity was initially very high (567 passes night−1 on‐track) and then declined by up to 40% in the following three years, but then fully recovered in the fifth year. This general pattern was evident both on‐ and off‐tracks for most taxa, though activity was three times greater on‐ than off‐track, highlighting the importance of these distinct habitat features for bats. Multivariate state‐space (MARSS) models predicted, unexpectedly, that high winter rainfall prior to our surveys was negatively related to activity for many taxa. In contrast, disturbance from timber harvesting or fire had weak or no identifiable effects on trends in activity for most taxa. One exception was Chalinolobus picatus (threatened), whose occupancy off‐tracks was negatively related to the extent of recent (<5 years) fire and to harvesting, though at the landscape scale, occupancy remained stable. This result, together with patterns for other bat taxa, suggests that disturbance effects were short‐lived/dispersed and/or environmental mitigations were effective at maintaining bat populations at a landscape level. Annual monitoring highlighted annual variation in activity and its implications when setting a baseline for monitoring. We also discuss modifications to future monitoring effort, based on the existing five years of data.

Species specific effects of prescribed burns on bat occupancy in northwest Arkansas

Due to the recent spread of white nose syndrome, it is imperative that managers understand the effects their management techniques have on bat species. Our research aims to determine the spatial and temporal variation in occupancy of bat species native to the Ozark Highlands and Boston Mountains of northwest Arkansas. Although prescribed burn units in this region are burned on a three-year rotation, it is not currently known how this treatment schedule affects bats. To determine the effects of prescribed burns on bat species including Myotis grisescens, Nycticeius humeralis, and Perimyotis subflavus, acoustic monitors and insect traps were deployed at 20 burned and 20 unburned sites that were visited twice, between April and November of 2017. Bat calls were analyzed for presence/absence data. Single season occupancy modeling was used to determine the effects of environmental covariates on probabilities of detection and occupancy. In total, 132,528 acoustic files were collected. The probability of detection for each bat species was affected by temperature or moon phase. Occupancy models indicated that probability of occupancy for all species was affected by seasonal changes and basal area (m2/Ha), and all but one were affected by prey biomass. These data indicate that although prescribed burns may have not directly affected bats, potential indirect effects of fire, basal area and insect biomass, appear to have significant impacts.

The effects of wildfire severity and pyrodiversity on bat occupancy and diversity in fire-suppressed forests

Wildfire is an important ecological process that influences species’ occurrence and biodiversity generally. Its effect on bats is understudied, creating challenges for habitat management and species conservation as threats to the taxa worsen globally and within fire-prone ecosystems. We conducted acoustic surveys of wildfire areas during 2014–2017 in conifer forests of California’s Sierra Nevada Mountains. We tested effects of burn severity and its variation, or pyrodiversity, on occupancy and diversity for the 17-species bat community while accounting for imperfect detection. Occupancy rates increased with severity for at least 6 species and with pyrodiversity for at least 3. Two other species responded negatively to pyrodiversity. Individual species models predicted maximum occupancy rates across burn severity levels but only one species occurred most often in undisturbed areas. Species richness increased from approximately 8 species in unburned forests to 11 in pyrodiverse areas with moderate- to high-severity. Greater accessibility of foraging habitats, as well as increased habitat heterogeneity may explain positive responses to wildfire. Many bat species appear well adapted to wildfire, while a century of fire suppression and forest densification likely reduced habitat quality for the community generally. Relative to other taxa, bats may be somewhat resilient to increases in fire severity and size; trends which are expected to continue with accelerating climate change.

Species Richness and Seasonality of Bat Occupancy on Northwestern National Wildlife Refuges

Abstract Bats are critical to ecosystem integrity but are being threatened by a variety of disease and anthropogenic stressors. Further, information is generally lacking on basic parameters necessary for long-term bat conservation in North America, including the timing of seasonal activity and location of overwintering sites. Between 2011 and 2016, we used passive acoustic recording equipment to collect and analyze 115,855 bat calls from six National Wildlife Refuges across three geographic areas in the northwestern United States; the majority of the data was collected from 2014 to 2015. We documented the presence of 16 species, with species richness varying from 6 to 15 species across sampled Refuges. This includes detection of two species outside of their expected ranges: western red bat Lasiurus blossevillii were found in the Great Basin and western pipistrelle Pipistrellus hysperus were found in the Northern Rockies. Overwintering bats were found across all three geographic areas, although only one species, western pipistrelle, was documented as active year round on more than one Refuge. Six species of bats were also identified as potentially overwintering within their respective areas. For suspected nonoverwintering species, including those considered susceptible to white-nose syndrome, dates of first detections began in early March to early May and last detections between early October and early November. Public lands established for conservation can provide important monitoring and conservation resources for bats.

Site occupancy of little brown bats (Myotis lucifugus) in response to salvage logging in the boreal forest

As a consequence of warmer winters, the frequency and severity of bark beetle infestations has increased in western North America, creating controversy over how to manage beetle-killed forests. Post-infestation salvage logging is increasingly used to reduce wildfire risk and recover the value of beetle-killed trees; however, the ecological consequences of this practice are poorly understood. We investigated the effects of post-infestation salvage logging in the boreal forest (Yukon, Canada) on habitat use by the little brown bat (Myotis lucifugus), a forest-dwelling species that is relatively tolerant of vegetative clutter and numerically dominant in boreal bat communities. We hypothesized that little brown bats would select closed-canopied sites, particularly at high latitudes where bats may be vulnerable to predators during midsummer when daylight is nearly continuous. Thus, we expected low occupancy rates in salvage-logged stands, particularly those with low tree retention. Because night length increases drastically after summer solstice, we also predicted that bat preference for closed canopies would decline by late summer. We monitored for bat presence with ultrasound detectors in 30 unlogged, beetle-affected stands and 60 small (<30 ha) salvage-logged stands of variable retention. We used occupancy models to test predictions regarding bat response to logging and associated changes in forest structure at local and landscape scales. Contrary to our predictions, occupancy by little brown bats was generally higher in salvage-logged stands, although differences were not statistically significant. Bat occupancy declined with increasing tree basal area, particularly during the second half of the summer when bats avoided forest stands with basal area >40 m2/ha. Our results suggest that vegetative clutter was a primary constraint for little brown bats. The observed clutter avoidance in late summer may have been caused by the presence of newly volant juveniles, which are not yet proficient at flying in clutter. In addition, bats may have shifted their preference to open habitats during late summer when nights were longer and darker, and perceived predation risk was likely reduced. Our study suggests that small patches of salvage-logged boreal forest may improve foraging habitat for little brown bats through clutter reduction; however, we caution that interpretation of our results should be limited to the tree retention levels and scale of logging at our sites. Additionally, the potential importance of unlogged areas as roosting habitat requires consideration before prescriptions are made on the proportion of the landscape to be salvage-logged.