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Reproductive bats switch frequently among roosts to select the most advantageous microclimates and avoid predation or parasitism. Many bats use human-made structures, such as bat boxes and buildings, in areas where natural structures are less abundant. Artificial structures, which may be warmer and larger than natural structures, may affect bat behavior and roost use. We studied Yuma Myotis (Myotis yumanensis) and Little Brown Myotis (M. lucifugus) in artificial structures at two sites to understand how roost conditions and reproductive pressures influenced roost switching in maternity colonies in the lower mainland of British Columbia, Canada. During summer 2019, we used Passive Integrated Technology (PIT tags and scanners) to track daily roosting locations of individuals. Yuma myotis and little brown myotis used at least five roosts at each site and switched almost daily among roosts. Bats were less likely to switch from roosts that were 25–42°C and switch roosts during lactation, particularly when the young were nonvolant. Our findings suggest that reproductive female myotis that use artificial roosts seek out warm roosts to limit energy expenditure and speed up offspring development. We also found that bats boxes were not thermally stable environments and the behavior of bats reflected temperature variability. Land managers should ensure that multiple nearby roosts are available to maternity colonies, as reproductive bats require a range of temperatures and roost types during summer. [ABSTRACT FROM AUTHOR]

Many temperate-climate bats migrate tens to hundreds of kilometers from hibernacula to summer habitat each spring and in the opposite direction each fall. Understanding the timing of migration can help reduce the risk of disturbance via anthropogenic activities, guide effective management and determine future impacts of a changing climate. We examined the influence of weather and day of year on the arrival and departure of Indiana bats (Myotis sodalis) monitored at a summer maternity colony site in central Indiana from 1998 to 2014, using emergence count data to track the timing of bat presence during the spring and fall migration seasons. We used an information theoretic approach to compare 23 models that predicted bat presence as a function of weather, climate and lunar illumination; these models predicted arrival of the first Indiana bat and the first observation of a colony in spring, and the last observation of a colony and the last bat observed in fall. Bats embarked on spring and fall migrations to the maternity colony area at approximately the same time each year (arriving ∼3 April and departing ∼7 October) and variation was accounted for by changes in weather. Spring arrival and colony formation were predicted by higher temperatures (x = 22.5°C for colony formation) and precipitation and lower wind speeds, whereas lower temperatures (x = 25.9°C for colony breakup) and precipitation and higher wind predicted colony breakup and departure in fall. Spring migration coincided with periods of increased winds and thus, we advocate for higher cut-in speeds for wind turbines during bat migration seasons. Resource managers should consider the entire time that bats are on the summer landscape when defining regulations and implementing conservation measures. [ABSTRACT FROM AUTHOR]

Indiana bats ( Myotis sodalis) are capable of exploiting ephemeral resources in structurally complex, interior forests. Consequently, surveying for this species is difficult, and even in areas harboring known populations, documenting presence remains a challenge. We aimed to determine what factors affected probability of detection ( p) and site occupancy (Ψ) for Indiana bats when sampling with acoustic bat detectors near an active maternity colony. From May to August 2012 and 2013, we passively sampled 71 random points near Indianapolis, Indiana, with Wildlife Acoustic SM2BAT+ detectors. On average, sampling occurred ∼2.2 km from maternity colony roosts, which contained ≥ 150 bats by mid-July. Habitat and landscape covariates were measured in the field or via ArcGIS. We reduced model covariates with Pearson's correlation and principal component analysis. Indiana bat calls were identified using Bat Call ID software. We used Presence 6.1 software and Akaike's Information Criteria to assess models for detectability and occupancy. Detectability of Indiana bats increased as 'forest closure' and mean nightly temperature increased, likely due to reduced clutter and increased bat activity, respectively. The null model best explained Ψ, but models were likely underpowered from few Indiana bat detections. Higher rates for Ψ were observed near agricultural lands, indicating this cover type may fulfill certain habitat requirements for Indiana bats within the study site. Overall, detection rates were low even when sampling near a concentrated population on its maternity grounds, likely due to limitations inherent to bat detector technologies. Managers should be aware of the limitations of using passive acoustic sampling as a means by which to document presence-absence for this endangered species. [ABSTRACT FROM AUTHOR]