Daniel J. Neubaum

Determining bat seasonal roost use, demographic rates (fidelity and survival), and movements are necessary metrics to rigorously evaluate population status and trends. Little is known about these metrics for Townsend’s big-eared bats (Corynorhinus townsendii), a state and federal sensitive species, in Colorado. Therefore, our objectives were to monitor daily use of a large maternity colony (∼ 900 bats) inside a gated mine from 2011 to 2025 by marking bats with PIT tags (n = 840), evaluate their tolerance of the disturbance, assess seasonal patterns, and estimate demographic rates for this species. Bats tagged as adults were regularly detected to reach 10 yr of age, with at least 1 individual reaching a minimum of 15 yr of age. Despite concerns of capture and tagging disturbance for this species, 90% of individuals were detected again at the maternity colony at least once during the same summer of tagging. We detected 46% of females and 41% of males at least once across subsequent years following tagging. Variation by age was apparent with juveniles detected during at least 1 subsequent maternity season at lower percentages than adults. Numbers of tagged individuals present varied seasonally but the pattern of seasonal variation was consistent across years. We confirmed autumn movement to a known hibernaculum in a cave 48 km north of the maternity roost for 31 tagged bats, indicating that summer colonies fragment for winter rather than moving as an intact group. These data represent the first documented summer-to-winter movement of PIT-tagged C. townsendii and suggest that short-distance, localized migrations to hibernacula are an over-wintering strategy for this species where resources permit. We documented loss of PIT tags by C. townsendii and accounted for it by generating minimum tag retention estimates. Apparent annual survival for adult females across all years was 0.74 (95% CI = 0.60–0.87), similar to that for other PIT tag studies of bat species. Adult females and juvenile males showed high site fidelity with yearly return probabilities above 0.95, whereas estimates for juvenile females were lower (0.80). Our data show that PIT tags can be used to mark and monitor C. townsendii safely, providing managers with rigorous demographic data that can guide management actions.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is presumed to have originated from wildlife and shares homology with other bat coronaviruses. Determining the susceptibility of North American bat species to SARS-CoV-2 is of utmost importance for making decisions regarding wildlife management, public health, and conservation. In this study, Brazilian free-tailed bats (Tadarida brasiliensis) were experimentally infected with two strains of SARS-CoV-2 (parental WA01 and Delta variant), evaluated for clinical disease, sampled for viral shedding and antibody production, and analyzed for pathology. None of the bats (n = 18) developed clinical disease associated with infection, shed infectious virus, or developed histopathological lesions associated with SARS-CoV-2 infection. All bats had low levels of viral RNA in oral swabs, six bats had low levels of viral RNA present in the lungs during acute infection, and one of the four bats that were maintained until 28 days post-infection developed a neutralizing antibody response. These findings suggest that Brazilian free-tailed bats are permissive to infection by SARS-CoV-2, but they are unlikely to contribute to environmental maintenance or transmission.

Numerous processes operating at landscape scales threaten bats (e.g., habitat loss, disease). Temperate bat species are rarely examined at commensurate scales because of logistical and modeling constraints. Recent modeling approaches now allow for presence‐only datasets, like those often available for bats, to assist with the development of predictive distribution models. We describe the use of presence‐only data and rigorous predictive distribution models to examine habitat selection by bats across Colorado, USA. We applied hierarchical Bayesian models to bat locations from 1906–2018 to examine relationships of 13 species with landscape covariates. We considered differences in type of activity (foraging, roosting, hibernation), seasonality (summer vs. winter), and scale (1, 5, 10, and 15‐km buffers). These findings generated statewide probability of use models to guide management of bat species in response to threats (e.g., white‐nose syndrome [WNS]). Analysis of buffers suggest selection of land cover and environmental covariates occurs at different scales depending on the species and activity. Pinyon (Pinus spp.)‐juniper (Juniperus spp.) appeared as a positive association in the highest number of models, followed by montane woodland, supporting the importance of these forest types to bats in Colorado. Other covariates commonly associated with bats in Colorado include westerly longitudes, and negative associations with montane shrubland. Mechanical treatments within pinyon‐juniper and montane woodlands should be conducted with caution to avoid harming bat communities. We developed hibernation models for only 2 species, making apparent the lack of winter records for bat species in the state. We also provide a composite predictive surface of small‐bodied bats in Colorado that delineates where these species, vulnerable to WNS, converge. This tool provides managers with focal points to apply surveillance and response strategies for the impending arrival of the disease.

Bats swarm when individuals aggregate, typically at caves or mines during autumn, and together repeatedly circle, dive, chase, and land (Fenton 1969). Swarming behavior could serve multiple social purposes including mating and orientation of young bats for migration or with potential hibernacula (Veith et al. 2004). Breeding during autumn swarming could enhance gene flow, as unrelated individuals would have a way of finding each other to mate (Rivers et al. 2006).

Conservation of roosts is regularly recommended as a strategy to decrease the risk of threats to local bat populations (e.g., white-nose syndrome). Determining whether a roost site plays a meaningful role in maintaining a local bat population can be difficult given the variability found in roost structure type, and use by season, duration, and sex. Here we provide land managers and biologists with guidelines to aid in the decision process for determining which roosts are biologically important in maintaining healthy bat populations at a local scale. We define methods for determining biologically important roost sites and provide a case study of their use on bat roosts in Colorado. To be considered biologically important, we suggest that a roost meet two primary criteria: 1) it is considered a hibernaculum, maternity roost, transient roost, colonial bachelor roost, or fall swarming site used by bat species that are gregarious roosters, hibernators, or are known to swarm, and 2) if the site is disturbed or lost, it could affect 5% or more of the local population of the species, as defined by the investigator. Additive measures to further evaluate the importance of the roost and assign higher conservation value include: 1) a roost used by a special status species and 2) large aggregations of bats where an estimated 20% or more of the local population is roosting or swarming at the site. We also provide definitions for the seasonality of roost types, examples of several real-life scenarios where management decisions have been made for roosts, and a worksheet that helps guide users through the process.