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Location of little brown bat (Myotis lucifugus) barn roost (Carpenter Ranch) and house roost (Rehder Ranch) in northwestern Colorado, USA
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White‐nose syndrome (WNS) has caused the death of millions of bats, but the impacts have been more difficult to identify in western North America. Understanding how WNS, or other threats, impacts western bats may require monitoring other roosts, such as maternity roosts and night roosts, where bats aggregate in large numbers.
Little brown bats (Myo...
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... These results suggest that the species mentioned above might fly frequently along the woodland edges to forage between night roosting events. Furthermore, night roosts have the potential to become day roosts, providing additional resources for adverse environmental changes [83,84]. ...
In grassland ecosystems, agriculture and urbanization are two main anthropogenic disturbances to native fauna. Nature preserves at the urban-agricultural interface may include diverse vegetation habitats, providing opportunities for native fauna. Limited research has examined the conservation value of such preserves to bats. We examined bat activity patterns at multiple temporal scales at Glacier Creek Preserve in Omaha, Nebraska, USA, between 2018 and 2020 via acoustic monitoring to identify what functional habitats it might provide to bats. We placed bat detectors along the forest edge and in the open, restored native prairies and open agricultural fields. A total of nine species were recorded at the preserve, including the endangered Myotis septentrionalis. Foraging activities were recorded for six species. The edge habitat had higher overall acoustic activities for three species (Eptesicus fuscus, Lasiurus borealis, and Lasiurus cinereus) and a higher proportion of foraging activities for two species (Lasiurus borealis and Lasiurus cinereus) than the open habitat. Lasiurus cinereus displayed activity peaks early at night, whereas Lasiurus borealis had activity peaks late. Results suggest that a medium-sized nature preserve at the urban-agricultural interface can provide roosts, commuting corridors, and foraging grounds for different bats. The conservation value of such nature preserves should not be overlooked.
... Indiana bats give birth to one pup per year (Thomson, 1982). Juvenile mortality rates of similar bat species are estimated to range from 45% to 71% (Schorr & Siemers, 2021), so we expected the population to increase by more than 50% but less than 100% from pre-to post-volancy. We saw a change in fitted density estimates ranging from −8% to 202% from pre-to post-volancy across all six conservation areas (Figure 2). ...
Bat population estimates are typically made during winter, although this is only feasible for bats that aggregate in hibernacula. While it is essential to measure summer bat population sizes for management, we lack a reliable method. Acoustic surveys should be less expensive and more efficient than capture surveys, and acoustic activity data are already used as indices of population size. Although we currently cannot differentiate individual bats by their calls, we can enter call counts, information on signal and detection angles, and weather data into generalized random encounter models to estimate bat density. We assessed the utility of generalized random encounter models for estimating Indiana bat ( Myotis sodalis ) population density with acoustic data collected at 51 total sites in six conservation areas in northeast Missouri, 2019–2021. We tested the effects of year, volancy period, conservation area, and their interactions on estimated density. Volancy period was the best predictor, with average predicted density increasing 60% from pre‐volancy (46 bats/km ² ) to post‐volancy (74 bats/km ² ); however, the magnitude of the effect differed by conservation area. We showed that passive acoustic surveys yield informative density estimates that are responsive to temporal changes in bat population size, which suggests this method may be useful for long‐term monitoring. However, we need more information to choose the most appropriate values for the density estimation formula. Future work to refine this approach should include assessments of bat behavior and detection parameters and testing the method's efficacy in areas where population sizes are known.
... as expected from earlier studies from small insectivorous bats (e.g. Giavi et al., 2014;Schorr & Siemers, 2021). The overall summer survival in the base-line scenario at these two locations must therefore be viewed as strongly influenced by these assumptions, rather than as a quantitative outcome this model. ...
Strong seasonality at high latitudes represents a major challenge for many endotherms as they must balance survival and reproduction in an environment that varies widely in food availability and temperature. To avoid energetic mismatches caused by limited foraging time and stochastic weather conditions, bats employ the energy‐saving state of torpor during summer to save accumulated energy reserves.
However, at high‐latitude small‐bats‐in‐summer face a particular challenge: as nocturnal foragers, they rely on the darkness at night to avoid predators and/or interspecific competition, but live in an environment with short, light summer nights, and even a lack of true night at the northernmost distributions of some bat species.
To predict optimal behaviour in relation to latitudinal variation in diurnal cycles, we constructed a stochastic dynamic programming model of bats living at high latitudes. Using a stochastic dynamic programming framework with values that are representative for our study system, we show that individual energetic reserves are a strong driver of daytime use of torpor and night‐time foraging behaviour alike, with these linked effects being both temperature‐ and photoperiod‐dependent.
We further used the model to predict survival probabilities at five locations across a latitudinal gradient (60.1° N to 70.9° N), finding that combinations of photoperiod and temperature conditions limited population distributions in the model.
To verify our model results, we compared predictions for optimal decisions with our own empirical data collected on northern bats (Eptesicus nilssonii) from two latitudes in Norway. The similarities between our predictions and observations provide strong evidence that this model framework incorporates the most important drivers of diurnal decision‐making in bat physiology and behaviour.
Comparing empirical data and model predictions also revealed that bats facing lighter night conditions further north restrict their mass gain, which strengthens the hypothesis that predation threat is a main driver of bat nocturnality. Our model findings regarding state‐dependent decisions in bats should contribute to the understanding of how bats cope with the summer challenges at high latitudes.
... Myotis lucifugus is a habitat generalist during summer, often using anthro-pogenic structures that are easily accessible. Maternity roosts represent many of the largest known aggregations of M. lucifugus in the West (Schorr and Siemers 2021). We envision a network of sentinel maternity roost sites where counts of bats could be made annually to track changes in numbers at both local and regional scales. ...
... comm.). Additionally, mark-recapture methods could be employed to better understand finer grained components of demographic parameters such as lifespan, annual survival rates, reproductive success, and changes in body condition over time (Schorr and Siemers 2021). Cumulatively, maternity roost monitoring might provide a deeper understanding of colony dynamics across the West. ...
White-nose syndrome (WNS) has notably affected the abundance of Myotis lucifugus (little brown myotis) in North America. Thus far, substantial mortality has been restricted to the eastern part of the continent where the cause of WNS, the invasive fungus Pseudogymnoascus destructans, has infected bats since 2006. To date, the state of Washington is the only area in the Western US (the Rocky Mountains and further west in North America) with confirmed cases of WNS in bats, and there the disease has spread more slowly than it did in the Eastern US. Here, we review differences between M. lucifugus in western and eastern parts of the continent that may affect transmission, spread, and severity of WNS in the West and highlight important gaps in knowledge. We explore the hypothesis that western M. lucifugus may respond differently to WNS on the basis of different hibernation strategies, habitat use, and greater genetic structure. To document the effect of WNS on M. lucifugus in the West most effectively, we recommend focusing on maternity roosts for strategic disease surveillance and monitoring abundance. We further recommend continuing the challenging work of identifying hibernation and swarming sites to better understand the microclimates, microbial communities, and role in disease transmission of these sites, as well as the ecology and hibernation physiology of bats in noncavernous hibernacula.
... Once the most abundant bat species in North America, little brown bats (LBBs) have undergone massive population declines in parts of the continent. However, in areas not yet decimated by the fungal pathogen that causes white-nose syndrome, these bats remain relatively abundant [22]. A pre-COVID-19 pandemic report suggested that a third of LBBs were infected with several distinct clades of Alphacoronaviruses, which persisted at low levels in the intestine [23]. ...
Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), believed to have originated from a bat species, can infect a wide range of non-human hosts. Bats are known to harbor hundreds of coronaviruses capable of spillover into human populations. Recent studies have shown a significant variation in the susceptibility among bat species to SARS-CoV-2 infection. We show that little brown bats (LBB) express angiotensin-converting enzyme 2 receptor and the transmembrane serine protease 2, which are accessible to and support SARS-CoV-2 binding. All-atom molecular dynamics (MD) simulations revealed that LBB ACE2 formed strong electrostatic interactions with the RBD similar to human and cat ACE2 proteins. In summary, LBBs, a widely distributed North American bat species, could be at risk of SARS-CoV-2 infection and potentially serve as a natural reservoir. Finally, our framework, combining in vitro and in silico methods, is a useful tool to assess the SARS-CoV-2 susceptibility of bats and other animal species.
... This may be particularly evident if climatic changes also negatively affect survival rates (e.g. Rézouki et al. 2016, Schorr & Siemers 2021, although the greater longevity and slower life history of insectivorous bats than rodents might compensate for this. Additionally, our results suggest that the mechanisms linking climate to reproductive traits are not well-studied in hibernating mammals. ...
Animals can respond to climate change through changes in behaviour, morphology or life‐history traits. Changes in life‐history traits do not occur independently, as they trade off or co‐evolve with other traits.
Hibernation is a life‐history trait used to cope with periods of low resource availability. The energetic and survival benefits of hibernation depend on environmental conditions. Climate change‐induced changes in hibernation patterns are therefore likely to affect other life‐history traits through trade‐offs.
We systematically reviewed the literature to: 1) identify studies testing for associations between climatic variables and life‐history traits in mammalian hibernators; and 2) assess variation in responses between species.
Air temperature was the most commonly measured climatic variable, and phenology of hibernation emergence was the most commonly studied life‐history trait. In most studies and species, emergence date became earlier, litter size increased and the number of interbout arousals increased with increasing air temperature.
Despite being considered key life‐history traits due to their potential to influence population dynamics, our search returned no studies on the effects of climatic variables on the age of primiparity or on the age distribution of reproduction.
Directions of associations between climatic variables and life‐history traits often differed between species, and both species‐ and sex‐specific variations occurred in response to climatic variables for some traits.
We highlight the importance of long‐term, species‐specific research, and the need for further studies on indirect effects of climatic cues on co‐adapted traits to understand the potential for mammalian hibernators to respond to ongoing and future climate change.
... Over many generations, colonies of building-roosting bats can become heavily dependent on these structures, roosting in the same roof or attic for much of the reproductive season and returning to the same structure across consecutive seasons (e.g. [22]). This dependency on a single roosting structure may put the colony at risk should this structure be lost and alternate roosts be unavailable. ...
Bats in urban environments depend on human-made structures or remnant natural habitats for roosting. Bat boxes are commonly used artificial structures that aim to replace lost tree or building roosts, but they are not a universal solution, or panacea, as few species use them, and other options exist that more closely mimic natural tree cavities. As long-lived mammals, bats may be lured into human-built structures with unstable conditions. These structures could act as ‘ecological traps’ if they suddenly become inaccessible with few other roost options available. Problems arising from the use of bat boxes, such as mortality events resulting from overheating, may reflect limited roost availability rather than inherent flaws in bat box designs. Mimicking a natural roosting area requires accommodating requisite roost switching. This can be accomplished in urban centres by manipulating existing trees or erecting multiple, varied bat boxes in close proximity, which could require purposeful urban planning. Engaging the public in community-driven bat conservation initiatives may hold the key to ensuring bats thrive in human-dominated landscapes. Here, we discuss problems associated with bat boxes and propose solutions, using case studies from Canada and Australia.KeywordsBat boxBat houseArtificial roostsOverheatingCommunity-driven conservation
... In many species, roost switching is asynchronous among bats within a colony, resulting in stochastic changes in the daily occupants of roosts (Kerth 2008). Although bats marked with passive integrated transponder (PIT) tags can be passively recaptured or resighted (Schorr and Siemers 2021), combining mark-recapture methods with emergence counts is an under-utilized approach for estimating abundance at a local level. ...
The spread of white-nose syndrome into western North America has caused concerns that bat species inhabiting the region will soon experience population declines like those seen to the east. However, much of the region lacks baseline estimates of abundance for bats believed to be susceptible to WNS due to a scarcity of known hibernacula, where populations are traditionally monitored. The goal of this study was to determine the abundance, roost fidelity, and activity patterns of summer colonies of female little brown myotis (Myotis lucifugus) in an area with no known hibernacula. To accomplish this, we subcutaneously implanted passive integrated transponder (PIT) tags into 297 female little brown myotis from 2015 to 2018 and installed radio-frequency identification (RFID) readers and antennas inside three maternity roosts in Yellowstone National Park. Bats occupied RFID-monitored roosts on 32% of days and were never detected at maternity roosts located > 16 km from where they were tagged. Roost fidelity varied throughout summer and was greatest during late gestation and early lactation. This allowed us to combine nightly scans of RFID-tagged bats with visual emergence counts to estimate the population of bats using two roosts located >16 km apart during 2017–2018. Population estimates of both colonies were markedly higher (N* = 208 ± 6 bats and N* = 836 ± 67 bats during 2018) than the number of bats seen during evening emergence (high counts of 127 and 222, respectively). Nocturnal visits of tagged bats to these roosts increased around the time of parturition, indicative of bats returning to nurse young. These data show that emergence count and PIT tag data can be combined to monitor bat population abundance and activity patterns in areas where hibernacula are absent or where their locations are unknown.
Passive integrated transponders (PIT tags) can aid in the collection of important demographic data for species for which other methods, such as GPS technology, are not suitable. PIT tags can be particularly suitable to monitor small and cryptic species like bats and permit inference on their behavioral ecology. Literature for several species of bats states that females change their nightly activity patterns—going out and in of the roost only once per night during gestation compared to several times during lactation. Hence, we tested whether PIT tag detection patterns could be used to infer reproductive status and parturition date of female bats. From 2017 to 2021, we recorded detections of PIT-tagged little brown (Myotis lucifugus) and northern long-eared bats (M. septentrionalis) at the entrance of 2 maternity roosts in Québec and Newfoundland, Canada. We also used the maternity roost in Québec as a case study to further evaluate the potential of this method to link behavior and demography and investigated factors affecting parturition date. We were able to infer reproductive status for 63% to 97% of tagged individuals detected during both the gestation and the lactation periods, and parturition date for 61% to 95% of reproductive individuals, depending on the year and roost. Early spring arrival at the roost and warm spring mean temperature at night were associated with earlier parturition dates. Herein, we highlight that PIT tag systems may be useful to detect changes in activity patterns of female bats and infer individual reproductive parameters, which is on the long-term less stressful for bats and easier for researchers. We demonstrate that this approach is useful to investigate intrinsic and extrinsic factors of reproductive parameters, improving our understanding of bat population dynamics resulting in more informed population management decisions.
The little brown bat ( Myotis lucifugus ) is an endangered species that occurs throughout most of North America. The recovery strategy for little brown bats in Canada identifies a need to understand habitat use and protect important bat habitat across the species' Canadian range; however, bat roosting habitat requirements have not been well studied in mountainous environments within the northern part of the species' range. Our objective was to understand the use of building and natural roosts by female little brown bats in the Canadian Rocky Mountains. Over two summers, we captured little brown bats in Banff, Yoho, and Kootenay National Parks, in Alberta and British Columbia, Canada, and tracked 49 females to their day roosts. Buildings were the only roost type used by radio‐tagged bats of all reproductive stages, the dominant roost type used throughout the reproductive period, and the only structures in which we located maternity colonies. Buildings also appeared to shape the distribution of foraging female and reproductive female bats such that few were captured at long distances from towns and building clusters. Compared with bats in more southern and in non‐mountainous areas, bats in our study area had delayed juvenile weaning and volancy, began hibernation early, and had low reproductive rates. We suggest that buildings are a key habitat for female little brown bats to persist at their current levels in our study area, by providing thermal conditions that promote overwinter survival; additional reproductive delays caused by torpor use in cool natural roosts would likely reduce juvenile and adult female overwinter survival below the levels required to sustain populations. Nevertheless, building colonies were unusually small, and bats had relatively low fidelity to particular building roosts, suggesting that building roosts may not consistently meet bats' needs. Some nonreproductive and pregnant females also frequently used natural roosts, particularly after colder nights; these roosts may be important in facilitating torpor and energy conservation for these bats. Because bats are long‐lived with low reproductive output and low juvenile survival, addressing the needs of both reproductive and nonreproductive individuals is important for population persistence.
