Winter Roosting by Eastern Red Bats in Ozark Mountain Forests of Missouri

The eastern red bat (Lasiurus borealis Müller, 1776) is a widespread species that roosts in evergreen or dead foliage suspended in trees during winter but retreats to leaf litter during colder periods. Roosting in leaf litter by eastern red bats makes them vulnerable to prescribed fires in winter. Using radio telemetry, we tracked 33 male eastern red bats to 101 winter (November–February) roosts and quantified roost locations, habitat surrounding roosts, and landscape attributes of roost locations. When roosting in trees, bats preferred oaks but generally avoided other tree species; they used pines in proportion to their availability. During colder periods, bats retreated to roosts in leaf litter where 21% suffered mortality either from predation/scavenging or unknown causes while roosting on the ground. Models of roost selection indicated that southerly aspect was the most important factor determining roost selection, and both tree- and leaf-litter roosts were predominately (≥94%) on upper south-facing slopes. Prescribed burning in late morning/early afternoon on clear days when temperatures under leaf litter are warmest in winter could reduce potential mortality by allowing faster arousal time for hibernating bats.

Mixed-species groups in bats: non-random roost associations and roost selection in neotropical understory bats

Background Mixed-species groups in animals have been shown to confer antipredator, foraging and other benefits to their members that may provide selective advantages. In most cases, however, it is unclear whether functional benefits are a principal driver of heterospecific groups, or whether groups simply result from simultaneous exploitation of common resources. Mixed-species groups that form independently of environmental conditions may, however, evidence direct benefits of species associations. Bats are among the most gregarious mammals, with sometimes thousands of individuals of various species roosting communally. Despite numerous potential functional benefits of such mixed-species roosting groups, interspecific attraction has never been shown. To explore alternative explanations for mixed-species roosting, we studied roost selection in a speciose neotropical understory bat community in lowland rainforest in Costa Rica. Long term roost data were recorded over 10 years in a total of 133 roosts comprising both natural roosts and structurally uniform artificial roosts. We modelled bat roost occupancy and abundance in each roost type and in forest and pasture habitats to quantify the effects of roost- and environmental variability. Results We found that bat species presence in natural roosts is predictable from habitat and structural roost parameters, but that the presence and abundance of other bat species further modifies roost choice. One third of the 12 study species were found to actively associate with selected other bat species in roosts (e.g. Glossophaga commissarisi with Carollia sowelli). Other species did not engage in communal roosting, which in some cases indicates a role for negative interspecific interactions, such as roost competition. Conclusions Mixed-species roosting may provide thermoregulatory benefits, reduce intraspecific competition and promote interspecific information transfer, and hence some heterospecific associations may be selected for in bats. Overall, our study contributes to an improved understanding of the array of factors that shape diverse tropical bat communities and drive the dynamics of heterospecific grouping in mammals more generally.

Temperature-dependent use of daily torpor attenuates the energetic consequences of habitat selection for a widespread bat

SummaryMany animals employ heterothermy to conserve energy during periods of inactivity, stress, or low resource availability. Unlike homeotherms, these heterotherms have some flexibility in body temperature. Unlike poikilotherms, heterotherms can maintain body temperatures independently from their environments. Heterotherms should thus exhibit fundamentally different responses to suboptimal environmental temperatures than either homeotherms or poikilotherms.In a species of heterothermic bat (Myotis thysanodes), we studied how daily torpor and roost selection could mitigate the energetic consequences of variation in ambient temperature. We then (1) quantified the relationship between ambient temperature and torpor use, (2) simulated daily energy expenditure over a range of roost temperatures, and (3) quantified the influence of roost temperature on roost selection.Bats did not select roosts with specific thermal characteristics, nor did ambient temperature alter patterns of roost selection. This was likely because bats could modulate use of torpor to maintain a consistent level of energy expenditure over the course of a day, irrespective of ambient temperature.Thermoregulatory processes in heterotherms differ from that of homeotherms and poikilotherms, including through behaviours as universal as habitat selection. Unlike homeotherms, bats face little pressure to select warm habitats to avoid heat loss during periods of inactivity—bats can use daily torpor to fully offset any increases in energy expenditure from maintaining homeothermy at colder temperatures.

Winter roost selection of Lasiurine tree bats in a pyric landscape

Day-roost selection by Lasiurine tree bats during winter and their response to dormant season fires is unknown in the southeastern United States where dormant season burning is widely applied. Although fires historically were predominantly growing season, they now occur in the dormant season in this part of the Coastal Plain to support a myriad of stewardship activities, including habitat management for game species. To examine the response of bats to landscape condition and the application of prescribed fire, in the winter of 2019, we mist-netted and affixed radio-transmitters to 16 Lasiurine bats, primarily Seminole bats (Lasiurus seminolus) at Camp Blanding Joint Training Center in northern Florida. We then located day-roost sites to describe roost attributes. For five Seminole bats, one eastern red bat (Lasiurus borealis), and one hoary bat (Lasiurus cinereus), we applied prescribed burns in the roost area to observe bat response in real-time. Generally, Seminole bats selected day-roosts in mesic forest stands with high mean fire return intervals. At the roost tree scale, Seminole day-roosts tended to be larger, taller and in higher canopy dominance classes than surrounding trees. Seminole bats roosted in longleaf (Pinus palustris), slash (Pinus elliotii) and loblolly pine (Pinus taeda) more than expected based on availability, whereas sweetbay (Magnolia virginiana), water oak (Quercus nigra) and turkey oak (Quercus laevis), were roosted in less than expected based on availability. Of the seven roosts subjected to prescribed burns, only one male Seminole bat and one male eastern red bat evacuated during or immediately following burning. In both cases, these bats had day-roosted at heights lower than the majority of other day-roosts observed during our study. Our results suggest Seminole bats choose winter day-roosts that both maximize solar exposure and minimize risks associated with fire. Nonetheless, because selected day-roosts largely were fire-dependent or tolerant tree species, application of fire does need to periodically occur to promote recruitment and retention of suitable roost sites.

Roost selection by Mauritian tomb bats (Taphozus mauritianus) in Lilongwe city, Malawi – importance of woodland for sustainable urban planning

Increasing urbanisation has led to a greater use of artificial structures by bats as alternative roost sites. Despite the widespread presence of bats, roost availability may restrict their distribution and abundance in urban environments. There is limited quantitative information on the drivers of bat roost selection and roosting preferences, particularly in African bats. We explore the factors influencing roost selection in the Mauritian tomb bat (Taphozous mauritianus), within an urban landscape in Lilongwe city, Malawi. Eight building and five landscape features of roosts were compared with both adjacent and random control buildings throughout the city. Bat occupied buildings were situated closer to woodland (mean 709m) compared to random buildings (mean 1847m) but did not differ in any other landscape features explored. Roosts were situated on buildings with larger areas and taller walls, suggesting bats select features for predator-avoidance and acoustic perception when leaving the roost. Bats preferred buildings with exposed roof beams which may provide refuge from disturbance. Whilst roosts are situated more often on brick walls, this feature was also associated with landscape features, therefore its importance in roost selection is less clear. These results are indicative that T. mauritianus selects roosts at both the building and landscape level. The selectivity of T. mauritianus in relation to its roost sites implies that preferred roosts are a limited resource, and as such, conservation actions should focus on protecting roost sites and the woodland bats rely on.

Patterns of roost site use by Asian hornbills and implications for seed dispersal

Animals spend a significant amount of time roosting. Therefore, understanding roosting patterns and the processes that influence roosting behaviour and roost site choice is essential. Hornbills exhibit interesting roosting patterns with some species roosting communally in large flocks. They are important seed dispersers and patterns of roost site use can have a significant influence on seed dispersal distributions and thereby on plant recruitment. We documented roost site use by four Great Hornbills (Buceros bicornis) and one Wreathed Hornbill (Rhyticeros undulatus) at a site in north-east India using GPS telemetry. We examined the influence of riverine habitats, nests and foraging range on roost selection. We determined the proportion of seeds that hornbills disperse at roosts and the dispersal distances of seeds dispersed at roosts from the source trees. Through telemetry, we found that roosts of Great Hornbills were generally in forested habitats. Our telemetry data showed that Wreathed Hornbill roosts were close to the river. These results were corroborated by observational data from roost sites where we had regular detections of relatively large flocks of Wreathed Hornbills and occasionally Great Hornbills. The roost sites were not close to the nest sites and were generally within the 95% kernel density diurnal activity ranges. Hornbills dispersed a small proportion of seeds at roost sites. Seeds dispersed at roost sites had almost twice the dispersal distances compared to those dispersed at non-roost sites. This study highlights variation in roost site pattern across individual hornbills and its implications for seed dispersal.