Tree Selection and Landscape Analysis of Eastern Red Bat Day Roosts

ABSTRACT Declining bat populations and increasing demands on forest resources have prompted researchers to investigate tree roost selection of forest bats. Few studies, however, have investigated different spatial scales and landscape pattern as criteria for selection of tree roosts. In 1999 and 2000, we radiotracked 23 eastern red bats (Lasiurus borealis) to 64 day roosts. Using univariate and multivariate comparisons, we tested roost tree variables with random tree data at 3 circular spatial scales: roost tree, plot, and landscape. We found 15 variables that were entered in a stepwise discriminant analysis to best differentiate between the roost and random samples; 11 (73.3%) were landscape variables measured with a geographic information system. On average (x̄ ± SE), red bats roosted in deciduous trees (42.0 ± 2.1 cm dbh) that were located in plots with more (3.1 ± 0.1 m²) basal area, higher (84.0 ± 1.3) percentage of canopy closure, and lower (27.2 ± 2.2) percentage of groundcover than random plots. At the landscape scale (by percent magnitude), red bat buffers (1,000-m-radius circle) had significantly less development (81.6%), less feeding operations (70.4%), more deciduous (52.9%) and pine forest (63.8%), and fewer local roads (5.4%) but more trails (94.1%), open water (61.4%), wetland areas (80.4%), and stream areas (63.1%) than random buffers. Red bat roost trees were significantly closer (χ² = 22.0088, df = 1, P < 0.001) to trails (106.2 ± 13.3 m) than to streams (279.4 ± 28.5 m). Our results suggest that red bats in our study area select roosts in mature riparian forests near trails, open water, and wetlands. The high percentage of landscape values in the discriminant analysis lends support to using landscape metrics as an investigative technique of resource selection. We recommend that managers consider landscape factors when protecting red bat day-roost habitat.     

Multi-Scale Assessment of Male Northern Yellow Bat Roost Selection

Knowledge of roost selection by northern yellow bats (Lasiurus intermedius) is limited to a small number of known roost locations. Yet knowledge of basic life history is fundamental to understanding past response to anthropogenic change and to predict how species will respond to future environmental change. Therefore, we examined male northern yellow bat roost selection on 2 Georgia, USA, barrier islands with different disturbance histories. Sapelo Island has a history of extensive disturbance and is dominated by pine (Pinus spp.) forests; Little Saint Simons Island has a limited disturbance history with maritime oak (Quercus spp.) forest as the dominant cover type. From March–July 2012 and 2013, we radio-tracked 35 adult male northern yellow bats to diurnal roosts and modeled roost characteristics at the plot and landscape scales. We located 387 roosts, of which 95% were in Spanish moss (Tillandsia usneoides) hanging in hardwood trees. On both islands, bats selected roost trees with larger diameters than surrounding trees and selected roost locations with greater open flight space (i.e., low midstory clutter) underneath. Roosts were located farther from open areas on Sapelo and closer to fresh water on Little Saint Simons compared to random locations. Lower availability of hardwood forest on Sapelo may have resulted in small-scale roost site selection (i.e., plot level) despite potential increased costs of commuting to water and open areas for foraging. In contrast, greater availability of hardwood forest on Little Saint Simons likely allowed selection of roosts closer to fresh water, which provides foraging and drinking opportunities. Our results indicate that mature hardwood trees in areas with low midstory clutter are important in male northern yellow bat roost selection, but landscape-level features have varying influences on roost selection, likely as a result of differences in disturbance history. Therefore, management will differ depending on the landscape context. Further research is needed to examine roost selection by females, which may have different habitat requirements. © 2020 The Wildlife Society.     

Effects of Hierarchical Roost Removal on Northern Long-Eared Bat (Myotis septentrionalis) Maternity Colonies

Forest roosting bats use a variety of ephemeral roosts such as snags and declining live trees. Although conservation of summer maternity habitat is considered critical for forest-roosting bats, bat response to roost loss still is poorly understood. To address this, we monitored 3 northern long-eared bat (Myotis septentrionalis) maternity colonies on Fort Knox Military Reservation, Kentucky, USA, before and after targeted roost removal during the dormant season when bats were hibernating in caves. We used 2 treatments: removal of a single highly used (primary) roost and removal of 24% of less used (secondary) roosts, and an un-manipulated control. Neither treatment altered the number of roosts used by individual bats, but secondary roost removal doubled the distances moved between sequentially used roosts. However, overall space use by and location of colonies was similar pre- and post-treatment. Patterns of roost use before and after removal treatments also were similar but bats maintained closer social connections after our treatments. Roost height, diameter at breast height, percent canopy openness, and roost species composition were similar pre- and post-treatment. We detected differences in the distribution of roosts among decay stages and crown classes pre- and post-roost removal, but this may have been a result of temperature differences between treatment years. Our results suggest that loss of a primary roost or ≤ 20% of secondary roosts in the dormant season may not cause northern long-eared bats to abandon roosting areas or substantially alter some roosting behaviors in the following active season when tree-roosts are used. Critically, tolerance limits to roost loss may be dependent upon local forest conditions, and continued research on this topic will be necessary for conservation of the northern long-eared bat across its range.     

Winter Roosting Ecology of Eastern Red Bats in Southwest Missouri

Abstract: Eastern red bats (Lasiurus borealis) have been found to overwinter in areas that can experience severe fluctuations in temperature. We examined the red bat's use of winter roosts in southwest Missouri, USA, for 2 winters (2003–2005). We found tree roosts in eastern red cedars (Juniperus virginiana) and hardwoods. Tree roost sites were located on the south side of trees, and we found roost trees on south-facing slopes. Roost sites occurred more frequently in the location with least canopy cover. Bats switched from tree roosts to leaf litter roosts when ambient temperatures approached or fell below freezing. We found habitat characteristics and aspect to be determining factors in the selection of leaflitter roosts. Management of overwintering red bats requires a diverse forest structure, including canopy gaps, stand-density variation, and leaf-bearing trees, including oaks (Quercus spp.).     

EFFECT OF HABITAT AND FORAGING HEIGHT ON BAT ACTIVITY IN THE COASTAL PLAIN OF SOUTH CAROLINA

Abstract: We compared bat activity levels in the Coastal Plain of South Carolina among 5 habitat types: forested riparian areas, clearcuts, young pine plantations, mature pine plantations, and pine savannas. We used time-expansion radio-microphones and integrated detectors to simultaneously monitor bat activity at 3 heights (30, 10, 2 m) in each habitat type. Variation in vegetative clutter among sampling heights and among habitat types allowed us to examine the differential effect of forest vegetation on the spatial activity patterns of clutter-adapted and open-adapted bat species. Moreover, monitoring activity at 30, 10, and 2 m permitted us to also compare bat activity above and below the forest canopy. We detected calls of 5 species or species groups: eastern red/Seminole bats (Lasiurus borealis/L. seminolus), eastern pipistrelles (Pipistrellus subflavus), evening bats (Nycticeius humeralis), big brown bats (Eptesicus fuscus), and hoary bats (Lasiurus cinerius). At 2 and 10 m, bat activity was concentrated in riparian areas, whereas we detected relatively low levels of bat activity in upland habitats at those heights. Activity was more evenly distributed across the landscape at 30 m. Bat activity levels above the forest canopy were almost 3 times greater than within or below the canopy. We detected significantly greater activity levels of 2 open-adapted species (hoary and big brown bats) above rather than within or below the forest canopy. However, activity levels of 2 clutter-adapted species (eastern red/Seminole bats and eastern pipistrelles) did not differ above, within, or below the forest canopy. Despite classification as a clutter-adapted species, evening bat activity was greater above rather than within or below the forest canopy. We believe our results highlight the importance of riparian areas as foraging habitat for bats in pine-dominated landscapes in the southeastern United States. Although acoustical surveys conducted below forest canopies can provide useful information about species composition and relative activity levels of bats that forage in cluttered environments, our results showing activity above canopy suggest that such data may not accurately reflect relative activity of bats adapted to forage in more open conditions, and therefore may provide an inaccurate picture of bat community assemblage and foraging habitat use.     

Urban Maternity-Roost Selection by Big Brown Bats in Colorado

Abstract: Despite prevalent use of anthropogenic structures by bats and the associated implications for public health, management, and bat conservation, very little quantitative information exists about urban roost characteristics and their selection by bats. During the summers of 2001 to 2004 we conducted fieldwork in Fort Collins, Colorado, USA, situated on the northern end of Colorado's Front Range, to address questions of roost selection by the big brown bat (Eptesicus fuscus). The city has experienced its greatest growth in the past half century, with its population increasing by 30% in the last decade. Similar growth in new buildings has occurred, with the number of new housing permits issued annually doubling in the past decade. We located 142 roosts using radiotelemetry or by citizen calls in response to a newspaper article and flyers. To determine characteristics of roost selectivity by bats, we compared variables for known maternity roosts and randomly selected buildings at microhabitat and landscape scales using logistic regression; we used an information theoretic approach to determine which variables were most important. We considered 44 and 100 buildings in the microhabitat and landscape scale analyses, respectively. At the microhabitat scale maternity roosts had exit points with larger areas that were higher from the ground and had warmer average temperatures than randomly selected buildings. At the landscape scale distances to similarly categorized roosts were smaller, and urbanization variables such as lower building density, higher street density, and lower traffic count density were most important. Results for variables important to urban-roosting big brown bats were often analogous to studies that characterized maternity roosts found in tree snags and rock crevices. In addition, changes in the landscape, not only in the form of anthropogenic structures but also in water availability and vegetation structure such as riparian forests, may have led to population increases and range expansions of the big brown bat. Because big brown bats appear to selectively choose specific combinations of characteristics found at maternity roosts, not all available structures can be considered suitable and exclusion from established maternity roosts may negatively impact bat populations.     

Calls in the Forest: A Comparative Approach to How Bats Find Tree Cavities

Although tree cavities are a particularly critical resource for forest bats, how bats search for and find new roosts is still poorly known. Building on a recent study on the sensory basis of roost finding in the noctule (Ruczynski et al. 2007), here we take a comparative approach to how bats find roosts. We tested the hypothesis that species' flight abilities and echolocation call characteristics play important roles in how well and by which cues bats find new tree roosts. We used the very manoeuvrable, faintly echolocating brown long-eared bat ( Plecotus auritus ) and the less manoeuvrable, louder Daubenton's bat ( Myotis daubentonii ) as study species. The species are sympatric in European temperate forests and both roost in tree cavities. We trained bats in short-term captivity to find entrances to tree cavities and experimentally manipulated the sensory cues available to them. In both species, cue type influenced the search time for successful cavity detection. Visual, olfactory and temperature cues did not improve the bats' performance over the performance by echolocation alone. Eavesdropping on conspecific echolocation calls played back from inside the cavity decreased search time in Daubenton's bat ( M. daubentonii ), underlining the double function of echolocation signals – orientation and communication. This was not so in the brown long-eared bat ( P. auritus ) that has low call amplitudes. The highly manoeuvrable P. auritus found cavities typically from flight and the less manoeuvrable M. daubentonii found more entrances during crawling. Comparison with the noctule data from Ruczyński et al. (2007) indicates that manoeuvrability predicts the mode of cavity search. It further highlights the importance of call amplitude for eavesdropping and cavity detection in bats.     

Habitat fragmentation and the prevalence of parasites (Diptera,Streblidae) on three Phyllostomid bat species

Ectoparasitism in bats seems to be influenced strongly by the type of roost preferred by the hosts, and group size; however, the effect of habitat loss and fragmentation on the prevalence of ectoparasites in bats has scarcely been studied. In northeastern Yucatan, Mexico, we estimated the prevalence of infestation by Streblidae flies in three phyllostomid bat species with different roost preferences (caves, trees, or both) in two types of landscape matrices (tropical semi‐deciduous forest and man‐made pastures) that differed in area of forest cover and the number of forest fragments. Habitat fragmentation and the presence of a contrasting matrix may limit the availability of roosts (trees) and the movement of bats across the landscape. Accordingly, we hypothesized higher prevalence of Streblidae infestation in the pasture matrix and in the group of bats that roost in trees. Bat abundance was higher in the pasture matrix; however, the prevalence of infestation was significantly higher in the continuous forest matrix and in bats that roosted in caves. The prevalence of some species of Streblidae was affected by habitat fragmentation in species that roost in caves, such as Desmodus rotundus, as well as those using foliage and caves, such as Artibeus jamaicensis. Our results provide evidence that some species of Streblidae may respond differently to habitat fragmentation than their hosts, generating changes to bat‐ectoparasite interactions in fragmented areas. Environmental variations involving roosts, not evaluated in this study, may influence our results, since these factors affect ectoparasite abundance and reproduction.     

Larger trees may support larger Indiana bat maternity colonies in a dynamic landscape

Indiana bats (Myotis sodalis), federally listed as endangered, are of management concern in eastern North America. While researchers quantified the habitat affinities of the species throughout the range, few studies have occurred in regions where populations are at high risk for wind energy development and changing climes. Central Illinois, USA, is a dynamic landscape where forest area has been increasing in recent decades (on public and private land) because of changing farming practices and increased habitat protections. The increasing availability of large diameter trees, increasing forest biomass, and changing forest compositions have the potential to influence Indiana bat roost habitat preferences. We assessed Indiana bat maternity roost selection at the tree and forest plot scale to characterize patterns of use in this region from 2017–2018. We predicted that large trees on the landscape would support large colonies of Indiana bats. We located bats in multiple species of trees including elm (Ulmus spp.), cottonwood (Populus deltoides), and shagbark hickory (Carya ovata). We documented larger maternity colonies sharing roosts than in previous studies from the 1980s in the same region. We suggest managers and regulatory agencies monitor Indiana bats in dynamic landscapes such as those with changing forest composition and biomass.     

Roost switching, roost sharing and social cohesion: forest-dwelling big brown bats, Eptesicus fuscus, conform to the fission-fusion model

We used radiotelemetry to quantify roost switching and assess associations between members of maternity colonies of forest-dwelling big brown bats. Bats remained loyal to small roosting areas of forest within and between years and switched trees often (). For radiotagged bats from the colony in one of these areas, roost-switching frequency was positively correlated with the number of different individuals with which tagged bats shared roosts. We quantified associations between pairs of bats using a pairwise sharing index and found that bats associated more often than predicted when roost and roostmate selection were random but that all tagged bats spent at least some days roosting in different trees, apart from preferred roostmates. Our results suggest that forest-dwelling big brown bats conform to a fission-fusion roosting pattern. Roost switching in forests may reflect the maintenance of long-term social relationships between individuals from a colony that is spread among a number of different trees on a given night. In this fission-fusion scenario, switching between trees, within a local area, could serve to increase the numbers of individuals with which bats maintain associations. We contend that roosting areas in forests are analogous to spatially large roosts in caves, mines and buildings.     

Roosting Behavior of Colonial and Solitary Flying Foxes in American Samoa (Chiroptera: Pteropodidae)1

We examined characteristics of roosting sites utilized by two flying fox species (Pteropus tonganus and P. samoensis) in American Samoa. The colonial roosting sites of P. tonganus were observed over a ten‐year period, including two years when severe hurricanes devastated bat populations and destroyed roost trees. Prior to the hurricanes, roosts were located on cliff faces above the ocean or steep mountainsides, locations that were either inaccessible to people or in protected areas where hunting was not allowed. In the years immediately following the hurricanes, P. tonganus colonies split into smaller groups that moved frequently to different locations. Four years after the second hurricane, colonies had coalesced and returned to many of the traditional roosting sites used before the hurricanes. Common tree species in upland and coastal forest were selected as roosts. The isolated locations selected for P. tonganus roosts were apparently the result of hunting pressure on the colonies. The solitary roosts of P. samoensis were observed during 29 months. Roosting bats were well concealed and hard to detect within the forest; even bats on exposed branches were cryptic. Mature primary forest was favored as roosting habitat. Individual bats used specific branches or trees as roosts and returned to them for up to 29 months. Unlike P. tonganus, people did not alarm roosting P. samoensis easily and some roosts were located near houses and along roads.     

Male Seminole Bat Winter Roost-Site Selection in a Managed Forest

Abstract: Understanding year-round roost-site selection is essential for managing forest bat populations. From January to March, 2004 to 2006, we used radiotelemetry to investigate winter roost-site selection by Seminole bats (Lasiurus seminolus) on an intensively managed landscape with forested corridors in southeastern South Carolina, USA. We modeled roost-site selection with logistic regression and used Akaike's Information Criterion for small samples (AIC_c) and Akaike weights to select models relating roost-site selection to plot- and landscape-level variables. We tracked 20 adult male bats to 71 individual roosts. Bats used a variety of roosting structures, including the canopy of overstory trees, understory vegetation, pine (Pinus spp.) needle clusters, and leaf litter. Roost height, structure type, and habitat type were influenced by changes in minimum nightly temperature. On warmer nights, bats selected taller trees in mature forest stands, but when minimum nightly temperatures were <4° C, bats typically were found roosting on or near the forest floor in mid-rotation stands. We recommend avoiding prescribed burning in mid-rotation stands on days when the previous night's temperature is <4 °C to minimize potential disturbance and direct mortality of bats roosting on or near the forest floor. We encourage forest managers to incorporate seasonal changes in roost-site selection to create year-round management strategies for forest bats in managed landscapes.     

Seeing the Forest through the Trees: Considering Roost-Site Selection at Multiple Spatial Scales

Conservation of bat species is one of the most daunting wildlife conservation challenges in North America, requiring detailed knowledge about their ecology to guide conservation efforts. Outside of the hibernating season, bats in temperate forest environments spend their diurnal time in day-roosts. In addition to simple shelter, summer roost availability is as critical as maternity sites and maintaining social group contact. To date, a major focus of bat conservation has concentrated on conserving individual roost sites, with comparatively less focus on the role that broader habitat conditions contribute towards roost-site selection. We evaluated roost-site selection by a northern population of federally-endangered Indiana bats (Myotis sodalis) at Fort Drum Military Installation in New York, USA at three different spatial scales: landscape, forest stand, and individual tree level. During 2007–2011, we radiotracked 33 Indiana bats (10 males, 23 females) and located 348 roosting events in 116 unique roost trees. At the landscape scale, bat roost-site selection was positively associated with northern mixed forest, increased slope, and greater distance from human development. At the stand scale, we observed subtle differences in roost site selection based on sex and season, but roost selection was generally positively associated with larger stands with a higher basal area, larger tree diameter, and a greater sugar maple (Acer saccharum) component. We observed no distinct trends of roosts being near high-quality foraging areas of water and forest edges. At the tree scale, roosts were typically in American elm (Ulmus americana) or sugar maple of large diameter (>30 cm) of moderate decay with loose bark. Collectively, our results highlight the importance of considering day roost needs simultaneously across multiple spatial scales. Size and decay class of individual roosts are key ecological attributes for the Indiana bat, however, larger-scale stand structural components that are products of past and current land use interacting with environmental aspects such as landform also are important factors influencing roost-tree selection patterns.     

Roosts of Allen's Lappet-Browed Bat in Northern Arizona

ABSTRACT In Arizona, USA, Allen's lappet-browed bat (Idionycteris phyllotis) forms maternity colonies in ponderosa pine (Pinus ponderosa) snags. There is little information on the roosting habitat of males. We used radiotelemetry to locate 16 maternity, 3 postlactating, and 2 bachelor roosts and combined data with unpublished data for maternity roosts (n = 11) located in 1993–1995. Most (96%) maternity roosts were in large-diameter (x̄ ± SE: 64 ± 2.7 cm) ponderosa pine snags under sloughing bark. Models that best predicted the probability of a snag's use as a maternity roost indicated bats selected taller snags closer to forest roads than comparison snags. Maternity roosts averaged 11 bats per roost (SE = 2, n = 15; from exit counts) and were an average distance of 1.6 km from capture sites (SE = 0.3, n = 17). Bachelor roosts were in vertical sandstone cliff faces in pinyon-juniper (Pinus edulis-Juniperus spp.) woodlands approximately 12 km from capture sites; these and other capture records in Arizona indicated sexual segregation may have occurred during the maternity season. Of 11 maternity snag roosts located in 1993–1995, only one continued to function as a roost. Resource managers should maintain patches of large-diameter ponderosa pine snags with peeling bark to provide maternity roosting habitat for Allen's lappet-browed bat.     

Summer tree roost selection by Rafinesque's big-eared bat

Roost requirements of most North American forest bats are well-documented, but questions remain regarding the ultimate mechanisms underlying roost selection. Hypotheses regarding roost selection include provision of a stable microclimate, space for large colonies, protection from predators, and proximity to foraging habitat, among others. Although several hypotheses have been proposed, specific mechanisms likely vary by species and geographic region. Rafinesque's big-eared bat (Corynorhinus rafinesquii) commonly roosts in trees with large basal hollows in the Coastal Plain of the southeastern United States. Our objective was to weigh evidence for hypotheses regarding selection of diurnal summer roosts by Rafinesque's big-eared bat at 8 study sites across the Coastal Plain of Georgia, USA. We used transect searches and radiotelemetry to locate roosts and measured 22 characteristics of trees, tree cavities, and surrounding vegetation at all occupied roosts and for randomly selected unoccupied trees. We evaluated 10 hypotheses using single-season occupancy models and used Akaike's information criterion to select the most parsimonious models. We located 170 tree roosts containing approximately 870 bats for our analysis. The best supported model predicted bat presence from cavity size, interior wall texture, and number of entrances. Because large cavities allow bats to fly and smooth walls impede attacks by terrestrial predators, our results are consistent with the hypothesis that bats select roosts that allow them to evade predators. However, data on predation rates are needed for a conclusive determination. Because trees suitable as roosts for Rafinesque's big-eared bat are rare in the landscape, protection of suitable forested wetland habitat is essential to provide current and long-term roost tree availability. © 2012 The Wildlife Society.     

Evening Bat Summer Roost-Site Selection on a Managed Pine Landscape

ABSTRACT Creation and maintenance of forested corridors to increase landscape heterogeneity has been practiced for decades but is a new concept in intensively managed southern pine (Pinus spp.) forests. Additionally, more information is needed on bat ecology within such forest systems. Therefore, we examined summer roost-site selection by evening bats (Nycticeius humeralis) in an intensively managed landscape with forested corridors in southeastern South Carolina, USA, 2003–2006. We radiotracked 53 (26 M, 27 F) adult evening bats to 75 (31 M, 44 F) diurnal roosts. We modeled landscape-level roost-site selection with logistic regression and evaluated models using Akaike's Information Criterion for small samples. Model selection results indicated that mature (≥40 yr) mixed pine-hardwood stands were important roost sites for male and lactating female evening bats. Upland forested corridors, comprised of mature pine or mixed pine-hardwoods, were important roosting habitats for males and, to a lesser extent, lactating females. Male roosts were farther from open stands and lactating female roosts were farther from mid-rotation stands than randomly selected structures. Our results suggest roost structures (i.e., large trees and snags) in mature forests are important habitat components for evening bats. We recommend maintaining older (>40 yr old) stand conditions in the form of forest stands or corridors across managed landscapes to provide roosting habitat. Furthermore, our results suggest that an understanding of sex-specific roost-site selection is critical for developing comprehensive guidelines for creating and maintaining habitat features beneficial to forest bats.     

Bat colony size reduction coincides with clear-fell harvest operations and high rates of roost loss in plantation forest

Clear-fell harvest of forest concerns many wildlife biologists because of loss of vital resources such as roosts or nests, and effects on population viability. However, actual impact has not been quantified. Using New Zealand long-tailed bats (Chalinolobus tuberculatus) as a model species we investigated impacts of clear-fell logging on bats in plantation forest. C. tuberculatus roost within the oldest stands in plantation forest so it was likely roost availability would decrease as harvest operations occurred. We predicted that post-harvest: (1) roosting range sizes would be smaller, (2) fewer roosts would be used, and (3) colony size would be smaller. We captured and radiotracked C. tuberculatus to day-roosts in Kinleith Forest, an exotic plantation forest, over three southern hemisphere summers (Season 1 October 2006–March 2007; Season 2 November 2007–March 2008; and Season 3 November 2008–March 2009). Individual roosting ranges (100% MCPs) post harvest were smaller than those in areas that had not been harvested, and declined in area during the 3 years. Following harvest, bats used fewer roosts than those in areas that had not been harvested. Over 3 years 20.7% of known roosts were lost: 14.5% due to forestry operations and 6.2% due to natural tree fall. Median colony size was 4.0 bats (IQR = 2.0–8.0) and declined during the study, probably because of locally high levels of roost loss. Post harvest colonies were smaller than colonies in areas that had not been harvested. Together, these results suggest the impact of clear-fell harvest on long-tailed bat populations is negative.     

The potential availability of roosting sites for lesser short‐tailed bats (Mystacina tuberculata) on Kapiti Island,New Zealand: Implications for a translocation

Abstract

Lesser short‐tailed bats (Mystacina tuberculata) have recently been translocated to Kapiti Island in an attempt to form a new population of this threatened species. However, the island's vegetation is regenerating, and there was doubt that the forests provided enough large trees with cavities for bats to roost in. This study measured the availability of tree‐trunk cavities of the right size for potential roost sites on Kapiti Island, and assessed if habitat restoration would be required to increase the translocation's chance of success. first, trees with cavities accessible to us were sampled in six of Kapiti Island's forest types. Size variables known to affect roost site selection by lesser short‐tailed bats at the tree and cavity level were measured. Trees were classified as containing cavities that could potentially provide suitable roosts if their values for all variables measured fell within the range of roosts used by lesser short‐tailed bats in natural populations. Roosts were classified as suitably sized for solitary bats or for colonies, using measurements from both types of roosts in natural populations. Second, the density of these potential roost cavities was calculated. Cavities of a size potentially suitable for colonies were found in four of the six forest types at densities ranging from 3.2 ± 3.2 Se to 52.4 ± 14.0 trees per ha. density of potential solitary roosts was much higher. Not all potential cavities will be suitable because they may be damp, poorly insulated, or have an unsuitable microclimate. Nevertheless, our estimates indicated that the two most extensive forest types each contained thousands of potential cavities of a size suitable for colonies of lesser short‐tailed bats. In addition, there were tens of thousands of cavities large enough to shelter solitary bats. Roost habitat restoration appears unnecessary to assist translocated Mystacina tuberculata on Kapiti Island.     

Bats relocate maternity colony after the natural loss of roost trees

Understanding the ephemerality of trees used as roosts by wildlife, and the number of roost trees needed to sustain their populations, is important for forest management and wildlife conservation. Several studies indicate that roosts are limiting to bats, but few studies have monitored longevity of roost trees used by bats over several years. From 2004–2007 in Cypress Hills Interprovincial Park, Saskatchewan, Canada, several big brown bats (Eptesicus fuscus) from a maternity group roosted in cavities in trembling aspen (Populus tremuloides) trees approximately 7 km southeast away from their original known roosting area (RA1). Using a long-term data set of the roost trees used by bats in this area from 2000–2007, we evaluated whether the movement of bats to the new roosting area (RA4) corresponded with annual and cumulative losses of roost trees. We also determined whether longevity of the roosts from the time we discovered bats first using them differed between the 2 roosting areas based on Kaplan-Meier estimates. Bats began using RA4 in addition to RA1 in 2004, when the cumulative loss of roost trees in RA1 over 3 consecutive years reached 18%. Most bats exclusively roosted in RA4 in 2007, when the cumulative loss of roost trees over 6 consecutive years had reached 46% in RA1. Annual survival for roost trees, from when we first discovered bats using them, was generally lower in RA1 than in RA4. Our results suggest that the movement of bats to the new roosting area corresponded with high losses of roost trees in RA1. This provides additional evidence that to maintain high densities of suitable roost trees for bats in northern temperature forests over several decades, management plans need to recruit live and dead trees in multiple age classes and stages of decay that will be suitable for the formation of new cavities. © 2019 The Wildlife Society.