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Reduced food availability is implicated in declines in avian aerial insectivores, but the effect of nutritional stress on mammalian aerial insectivores is unclear. Unlike birds, insectivorous bats provision their young through lactation, which might protect nursing juveniles when prey availability is low but could increase the energetic burden on lactating females. We analyzed a 15‐year capture–mark–recapture data set from 5312 individual little brown myotis (Myotis lucifugus) captured at 11 maternity colonies in northwestern Canada, to test the hypothesis that nutritional stress is impacting these mammalian aerial insectivores. We used long‐bone (forearm [FA]) length as a proxy for relative access to nutrition during development, and body mass as a proxy for access to nutrition prior to capture. Average FA length and body mass both decreased significantly over the study period in adult females and juveniles, suggesting decreased access to nutrition. Effect sizes were very small, similar to those reported for declining body size in avian aerial insectivores. Declines in juvenile body mass were only observed in individuals captured in late summer when they were foraging independently, supporting our hypothesis that lactation provides some protection to nursing young during periods of nutritional stress. Potential drivers of the decline in bat size include one or both of (1) declining insect (prey) abundance, and (2) declining prey availability. Echolocating insectivorous bats cannot forage effectively during rainfall, which is increasing in our study area. The body mass of captured adult females and juveniles in our study was lower, on average, after periods of high rainfall, and higher after warmer‐than‐average periods. Finally, survival models revealed a positive association between FA length and survival, suggesting a fitness consequence to declines in body size. Our study area has not yet been impacted by bat white‐nose syndrome (WNS), but research elsewhere has suggested that fatter bats are more likely to survive infection. We found evidence for WNS‐independent shifts in the body size of little brown myotis, which can inform studies investigating population responses to WNS. More broadly, the cumulative effects of multiple stressors (e.g., disease, nutritional stress, climate change, and other pressures) on mammalian aerial insectivores require urgent attention. [ABSTRACT FROM AUTHOR]

The bat fauna of northwestern Canada remains poorly known, principally owing to a lack of dedicated surveys across this vast region. To better assess the diversity of bats in the region, we compiled records from several acoustic survey projects and capture sessions whose purpose was to inventory bats in Yukon and northwestern British Columbia (BC) from 2013 to 2018. During our surveys we obtained the 1st apparent acoustic records for Yuma Myotis (Myotis yumanensis), Californian Myotis (M. californicus), Long-eared Myotis (M. evotis), Silver-haired Bat (Lasionycteris noctivagans) and Eastern Red Bat (Lasiurus borealis) from this region. We also captured 2 Long-eared Myotis in northwestern BC. Additionally, our surveys provided range extensions of Northern Myotis (M. septentrionalis), Long-legged Myotis (M. volans), and Hoary Bat (Lasiurus cinereus). Finally, by deploying bat detectors in late autumn, and in some cases throughout the winter, we provide data about seasonal patterns for bat activity in some locations, revealing that bats in northwestern BC may be active as late as 29 October and emerge as early as 30 March, a pattern similar to that observed in southern BC. By combining data from several disparate surveys, conducted for different reasons by different researchers, we were able to provide a fuller picture of the bat fauna of this vast region. Our data provides further evidence that the bat fauna of northwestern Canada is richer than previously documented. [ABSTRACT FROM AUTHOR]

Little brown bats (Myotis lucifugus) are a widely distributed species in North America that have been decimated by the fungal disease white-nose syndrome. As such, little brown bats are the focus of monitoring and research initiatives that often include capturing and handling free-ranging individuals. We examined the stress response of 198 adult female little brown bats after being captured from three bat houses, during the summer. Our objective was to inform best practices to researchers capturing and handling bats in the wild. We compared the stress response among bats held for <3 min (baseline), 15–30 min, or >30 min, and then among bats held alone or in a group with conspecifics. We measured the levels of plasma total and free cortisol, maximum corticosteroid binding capacity (MCBC), and blood glucose. Relative to baseline, total and free cortisol levels were significantly higher in bats held for 15–30 min and higher still in those held for > 30 min. Blood glucose levels were elevated after >30 min of holding. MCBC levels showed no differences among holding times. We detected a weak effect of social holding condition, with solitary-held bats having lower total cortisol levels than group-held bats, but MCBC, free cortisol, and blood glucose levels showed no effect of social holding condition. Our findings demonstrate that capture time should be minimized and suggest that little brown bats should be handled and released within 30 min of capture as means of reducing stress. Further, solitary holding did not appear to increase stress measures, which supports holding bats individually after capture, instead of in groups, to reduce risk of pathogen and parasite transmission. [ABSTRACT FROM AUTHOR]

The boreal forest is the largest intact forest in the world, and a refuge for species experiencing range retractions as a consequence of climate and landscape change. Yet, large tracts of the boreal forest are threatened by the cumulative impacts of climate change, natural resource extraction, agriculture, and urbanization, perhaps warranting a shift in focus from biodiversity conservation in intact wilderness to that in anthropologically modified landscapes. We investigated landscape features that influence the distribution of the endangered little brown bat (Myotis lucifugus) in an urbanizing boreal landscape at two spatial scales. We hypothesized that little brown bat activity would be influenced by proximity to available building roosts, because roosts are a potential limiting factor for boreal bats. Secondarily, we predicted that bats would use potential foraging habitat, such as waterbodies, and would avoid young, cluttered forests at the landscape scale. We conducted acoustic surveys of bat activity at 210 sites distributed across the study area in Yukon, Canada, within 1‐km grid cells. We tested a priori hypotheses with a set of candidate regression models, accounting for spatial autocorrelation. Our hypothesis about the relative importance of anthropogenic roosts was not supported. Little brown bats were equally active in urban areas (high building density) and rural areas (low building density), perhaps because roosts were adequately available throughout the region. Instead, habitat use was driven by the distribution of potential foraging habitat, particularly waterbodies, which are important sources of aerial insect prey. Little brown bats also avoided young (≤100‐yr‐old) forest at the landscape scale (including areas regenerating after fire), which may have been poor foraging or roosting habitat, and used areas with a smaller agricultural and industrial footprint. Our results suggest that waterbodies and mature forest are important little brown bat habitats that should be protected from urban encroachment. Proactive conservation of important habitat for species at risk is still possible throughout much of the boreal forest, where human densities are comparatively low and the urban footprint is currently small. [ABSTRACT FROM AUTHOR]

Identifying habitat features that may influence the survival and fitness of threatened species is often constrained by a lack of information about the appropriate scale for habitat conservation efforts. Canada's Species at Risk Act lists little brown bats Myotis lucifugus as Endangered and there is a need to determine the scale for delineating important summer habitat features that should be protected. We used a 19-y dataset of banded little brown bats in a 15,000-km2 area of southern Yukon, Canada, to examine fidelity to roost sites and potential foraging areas. We captured and banded 4,349 bats during 208 live-trapping sessions at maternity roosts. Adult females used multiple roosts during the maternity period, separated by up to 6.1 km, within foraging areas, to which individuals exhibited fidelity. Our fidelity rates (≤ 60.5%) are the lowest, and roost-switching rates (≤ 35.5%) the greatest, reported for little brown bats. A small percentage (14.0–20.7%) of females banded as juveniles returned to their natal roosts or foraging areas as adults. We infrequently observed long-distance (25–200 km) switching to novel foraging areas (< 1% of banded bats). We established bat houses to mitigate the loss of a cabin roost; 46.3% of the bats banded at the cabin occupied these houses. The longest documented period of roost fidelity was 18 y, by a female banded as an adult. Roost fidelity by returning adult females declined annually by 3.8–5.3% due to natural mortality, roost switching, or dispersal. Having a choice of multiple maternity roosts within a foraging area may permit little brown bats to select optimal microclimatic conditions throughout the maternity season. Given that fidelity to foraging areas may be higher than to specific roost sites for little brown bats, identification of summer habitat based on foraging areas may be a more effective conservation strategy than relying solely on roost sites. [ABSTRACT FROM AUTHOR]

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Three adult male Northern Long-eared Bats, Myotis septentrionalis, were captured in mist nets in July 2004 in the LaBiche River Valley, southeastern Yukon. These are the first records of M. septentrionalis in the Yukon. Further survey work is needed to delineate the extent of the range and population structure of this and other species of bats in northwestern North America. [ABSTRACT FROM AUTHOR]

We used radiotelemetry and random exit counts to determine roost site selection by male northern long-eared bats (Myotis septentrionalis) and unidentified Myotis, either northern long-eared or little brown bats (M. lucifugus) in a conifer-dominated, mixedwood forest landscape in central Ontario, Canada. We compared the characteristics of snags used as roosts (n = 26), with randomly located snags and random points (n = 52 and 50, respectively), at three spatial scales: focal tree, surrounding forest, and landscape. Snags used as roost sites by these bats differed from random snags for 19 of the 23 variables measured (P < 0.05). Logistic regression models were derived which suggested that the bats selected large snags, in open canopies, of intermediate stages of decay, that were located in upland areas, but away from water bodies. Bats may have selected roost sites for their thermal advantage in the mornings, as most used cavities or bark on the south and east sides of snags. To ensure that snags of appropriate characteristics persist for these two species of Myotis, forest managers in the northern Great Lakes forest region should retain, and manage for, large white pine (Pinus strobus) and trembling aspen (Populus tremuloides) snags at sites in forests that meet these criteria. Such a regime is possible under a selection harvest that is normally practiced in these mixedwood forest types. [Copyright &y& Elsevier]

• Little brown bat occupancy was unaffected by logging after a bark beetle outbreak. • Habitat use by bats in salvage-logged stands did not vary with tree retention. • Bat occupancy declined in unsalvaged forest stands with basal area >40 m2/ha. • Bats avoided cluttered forests in late summer when juveniles were present. 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. [ABSTRACT FROM AUTHOR]

Accidental mortality of bats is not often observed or reported in the literature. It may, however, have an impact on population size and structure. We report an observation of 53 Little Brown Bats (Myotis lucifugus) being trapped and drowned in a home-made rodent trap at an abandoned cabin in southern Yukon. Traps of this design may be commonly used in the boreal forest. We recommend not using such traps in cabins that are used by colonies of bats. [ABSTRACT FROM AUTHOR]