Movements and Resource Selection of the Northern Long-Eared Myotis (Myotis septentrionalis) in a Forest—Agriculture Landscape

Spatial and temporal activity patterns among sympatric tree-roosting bat species in an agriculturally dominated great plains landscape

In agroecosystems, bats can provide a critical ecosystem service by consuming night-flying insect pests. However, many bats also face intense population pressures from human landscape modification, global change and novel diseases. To better understand the behavioral activity of different bat species with respect to space, time, habitat, and other bat species in this environment, we investigated species correlations in space and time over row crop agricultural fields. We used acoustic grids to document spatial and temporal co-occurrence or avoidance between bats and recorded eight species across the 10 field sites we sampled. All species significantly overlapped in two-dimensional space and displayed considerable temporal overlap during the night, yet often exhibited significantly different temporal activity patterns, suggesting fine scale partitioning behavior. Conversion of land to agriculture is likely to increase globally, making it critical to better understand how bat species interact with one another and the landscape to facilitate persistence in these human altered ecosystems.

Unique Land Cover Classification to Assess Day-Roost Habitat Selection of Northern Long-Eared Bats on the Coastal Plain of North Carolina, USA

Reproductively successful and over-wintering populations of the endangered northern long-eared bat (Myotis septentrionalis) have recently been discovered on the Coastal Plain of North Carolina. Empirical data on resource selection within the region is limited, likely hindering management of these coastal forests. Our objectives were to determine roosting home range size, selection of day-roost tree species, second- and third-order roosting habitat selection, and to quantify the overall availability of resources in the surrounding landscape. We found core and peripheral roosting home range estimates were large, yet similar to observations from other areas of contiguous forests. Prior to juvenile volancy, female northern long-eared bats appear to select red maple (Acer rubrum), water ash (Fraxinus caroliniana), and loblolly pine (Pinus taeda) as day-roosts, but then use sweetgum (Liquidambar styraciflua), swamp bay (Persea palustris), and water tupelo (Nyssa aquatica) after juvenile volancy. At the second-order spatial scale, roosting home ranges were associated with woody wetlands farther from anthropogenic development and open water. However, within the third-order scale, northern long-eared bats were associated with undeveloped woody wetlands and upland forests, areas containing shorter trees and occurring proximal to open water. Peripheral and core areas were predicted to comprise approximately 20% of the local landscape. Our results show that complex and large tracts of woody wetlands juxtaposed with upland forests in this part of the Coastal Plain may be important for northern long-eared bats locally, results largely consistent with species management efforts in eastern North America.

Acoustic and Genetic Data Can Reduce Uncertainty Regarding Populations of Migratory Tree-Roosting Bats Impacted by Wind Energy

Wind turbine-related mortality may pose a population-level threat for migratory tree-roosting bats, such as the hoary bat (Lasiurus cinereus) in North America. These species are dispersed within their range, making it impractical to estimate census populations size using traditional survey methods. Nonetheless, understanding population size and trends is essential for evaluating and mitigating risk from wind turbine mortality. Using various sampling techniques, including systematic acoustic sampling and genetic analyses, we argue that building a weight of evidence regarding bat population status and trends is possible to (1) assess the sustainability of mortality associated with wind turbines; (2) determine the level of mitigation required; and (3) evaluate the effectiveness of mitigation measures to ensure population viability for these species. Long-term, systematic data collection remains the most viable option for reducing uncertainty regarding population trends for migratory tree-roosting bats. We recommend collecting acoustic data using the statistically robust North American Bat Monitoring Program (NABat) protocols and that genetic diversity is monitored at repeated time intervals to show species trends. There are no short-term actions to resolve these population-level questions; however, we discuss opportunities for relatively short-term investments that will lead to long-term success in reducing uncertainty.

Occurrence of a forest-dwelling bat, northern myotis (Myotis septentrionalis), within Canada’s largest conurbation

While some species thrive in urban areas, many are absent from such environments. Those that are successful often have high behavioural flexibility that allows them to exploit new niches in a human-modified landscape. Northern myotis (Myotis septentrionalis) is an endangered bat species rarely identified in urban areas, though it is unclear whether this is due to absence or difficulties in surveying. We investigated the ecology of a population of northern myotis within Canada’s largest conurbation, including reproductive status, roosting preference, and movements. Using capture surveys, we confirmed the presence of reproductive females and healthy juveniles over two seasons. Using radio telemetry and acoustic surveys, we identified a cluster of tree roosts in the centre of the forest, and foraging areas concentrated around waterways within the bounds of the forest. These observations suggest the roosting and movement ecology of this population is similar to that observed for this species in rural environments, despite the urban surroundings. Our results suggest that northern myotis is not a synurbic species but can occur within urbanized environments when suitable habitat is available. We suggest that large forest patches with mature, interior forest cover are likely to be an important resource for northern myotis, and they will be vulnerable to the loss or fragmentation of these features in rapidly urbanizing landscapes. These findings are highly relevant to the ecology and preservation of northern myotis and present a case for greater consideration of this species in urban forests.

Bats partition activity in space and time in a large, heterogeneous landscape

Diverse species assemblages theoretically partition along multiple resource axes to maintain niche separation between all species. Temporal partitioning has received less attention than spatial or dietary partitioning but may facilitate niche separation when species overlap along other resource axes. We conducted a broad-scale acoustic study of the diverse and heterogeneous Great Smoky Mountains National Park in the Appalachian Mountains. Between 2015 and 2016, we deployed acoustic bat detectors at 50 sites (for a total of 322 survey nights). We examined spatiotemporal patterns of bat activity (by phonic group: Low, Mid, and Myotis) to test the hypothesis that bats partition both space and time. Myotis and Low bats were the most spatially and temporally dissimilar, while Mid bats were more general in their resource use. Low bats were active in early successional openings or low-elevation forests, near water, and early in the evening. Mid bats were similarly active in all land cover classes, regardless of distance from water, throughout the night. Myotis avoided early successional openings and were active in forested land cover classes, near water, and throughout the night. Myotis and Mid bats did not alter their spatial activity patterns from 2015 to 2016, while Low bats did. We observed disparate temporal activity peaks between phonic groups that varied between years and by land cover class. The temporal separation between phonic groups relaxed from 2015 to 2016, possibly related to changes in the relative abundance of bats or changes in insect abundance or diversity. Temporal separation was more pronounced in the land cover classes that saw greater overall bat activity. These findings support the hypothesis that niche separation in diverse assemblages may occur along multiple resource axes and adds to the growing body of evidence that bats partition their temporal activity.

Qualitative synthesis of temperate bat responses to silvicultural treatments—where do we go from here?

Most bat species depend on forests for roosting, foraging, and drinking during part or all of their life cycles. Many of the world’s forests are managed using a variety of silvicultural treatments and, over the past 40 years, researchers have studied the responses of bats to these treatments. I carried out a qualitative synthesis of the literature on roosting and foraging responses of temperate insectivorous bats to silvicultural treatments at the stand level to determine what treatments may be most compatible with conservation and to guide future research. Eighty-eight studies from Canada, the United States, Europe, Australia, and New Zealand, met review criteria. Based on my results, foraging and commuting habitat use was less affected by changes in forest structure and composition than roost habitat use. Mid-rotation treatments that reduce clutter while retaining overstory structure (e.g., thinning and fire) had more neutral and positive effects than treatments that removed all or most of the overstory. Based on an examination of the methods and assumptions of the 88 studies included in this review, I conclude that future studies should: 1) strive to account for treatment effects on detection probability of bats when using acoustic detectors; 2) examine responses of bats to silvicultural treatments outside the maternity season; 3) examine demographic and physiological responses to silvicultural treatments in addition to habitat use to fully understand the effects of these treatments on bat populations; and 4) use stand-level data to model forest management effects across large landscapes and over long time periods.

Systematic Review of the Roost-Site Characteristics of North American Forest Bats: Implications for Conservation

Continued declines in North American bat populations can be largely attributed to habitat loss, disease, and wind turbines. These declines can be partially mitigated through actions that boost reproductive success; therefore, management aimed at promoting availability of high-quality roosting habitat is an important conservation goal. Following the principles of the umbrella species concept, if co-occurring species share similar roost-tree preferences, then management practices targeting one species may confer conservation benefits to another. We conducted a systematic review of roost-site characteristics of thirteen species inhabiting eastern temperate forests to: (1) synthesize existing knowledge across species; (2) assess niche overlap among co-occurring species; and (3) evaluate the potential for currently protected species to serve as conservation umbrellas. We performed multivariate ordination techniques to group species based on the seven most-reported roost-site characteristics, including tree species, diameter at breast height, tree health, roost type, tree height, canopy closure, and roost height. Species sorted into three roosting guilds: (1) southern wetland inhabitants; (2) foliage specialists; and (3) dead tree generalists. Myotis septentrionalis and Perimyotis subflavus had significant roost-niche overlap with five and four other species respectively, and their existing protections make them suitable umbrellas for other bats in the North American eastern temperate forests.

Predicting landscape-scale summer resource selection for the northern long-eared bat (Myotis septentrionalis) in Iowa

The northern long-eared bat (Myotis septentrionalis) is currently listed as threatened under the U.S. Endangered Species Act largely due to population declines resulting from the spread of white-nose syndrome in North America. White-nose syndrome was confirmed in Iowa in 2015, emphasizing a need to closely monitor populations of M. septentrionalis statewide. We applied presence-only models to predict landscape-scale resource selection by M. septentrionalis using roost tree observations and mist net captures from various research and environmental assessment projects in Iowa (2003–2015). We used a simultaneous autoregressive (SAR) model to account for residual spatial autocorrelation in our compiled data set and estimate the proportional probability of use of summer habitats for M. septentrionalis. We estimated SAR models using four environmental predictor variables measured at two landscape scales (0.5- and 2.4-km) representative of M. septentrionalis home range sizes in North America. The SAR models resulted in high predictive fit with withheld test observations and an independent data set of acoustic detections of M. septentrionalis from recent surveys (2016–2018), indicating a significant positive relationship existed between habitat quality (as an index of selection) and distribution of M. septentrionalis at landscape scales. At both spatial scales, M. septentrionalis showed positive selection of closed canopy interior forest, bottomland hardwood forest, and total perennial stream length, whereas at the 0.5-km scale, M. septentrionalis also showed a positive association with open canopy forest. Our models indicated that up to 7.0% and 8.5% of the state was comprised of potentially suitable forested summer habitats for M. septentrionalis for 0.5- and 2.4-km scales, respectively. Our models also indicated the distribution of highly selected habitats at landscape scales in Iowa and accurately predicted independent observations of M. septentrionalis in areas of the state where no capture efforts have occurred. This study provides methods to predict landscape-scale resource selection and distribution for bats where multiple fine-scale data sources exist across broad geographic regions.

Variation in regional and landscape effects on occupancy of temperate bats in the southeastern U.S

Habitat loss, wind energy development, and the disease white-nose syndrome are major threats contributing to declines in bat populations in North America. In the southeastern US in particular, the recent arrival of white-nose syndrome and changes in landscape composition and configuration have driven shifts in bat species populations and distributions. Effective management strategies which address these large-scale, community-level threats require landscape-scale analyses. Our objective was to model the relationship between ecoregional and landscape factors and occupancy by all bat species in South Carolina, USA, during summer. We conducted acoustic surveys from mid-May through July 2015 and 2016 and evaluated temporally dynamic occupancy models for eight bat species or species groups at the 100 km2 level. We found significant effects of landscape factors such as ecoregion and forest edge density for three species, but habitat condition effects were not statistically significant for five other species. Thus, for some species, site-use analyses may be more appropriate than larger scale occupancy analyses. However, our occupancy predictions generally matched statewide historical distributions for all species, suggesting our approach could be useful for monitoring landscape-level trends in bat species. Thus, while our scale of study was likely too coarse for assessing fine-scale habitat associations for all bat species, our findings can improve future monitoring efforts, inform conservation priorities, and guide subsequent landscape-scale studies for bat species and community-level responses to global change.

Situational and Age-Dependent Decision Making during Life Threatening Distress in Myotis macrodactylus

Echolocation and audiovocal communication have been studied extensively in bats. The manner in which these abilities are incorporated within escape behaviors during life-threatening distress is largely unknown. Here we tested the hypothesis that behavioral response profiles expressed during distress are relatively stereotypic given their evolutionary adaptations to avoid predators. We subjected juvenile and adult big-footed myotis (Myotis macrodactylus) to a sequence of three types of life threatening distress: 1) trapping them in a mist-net (environmental threat), 2) approaching them when trapped (predator threat), and 3) partially restraining their freedom to move (arrest), and recorded their escape behavior in each of the three conditions. Response profiles differed across individuals and with the context in which they were expressed. During environmental and predator threat, bats displayed significantly more biting and wing-flapping behaviors and emitted more echolocation pulses than during arrest. Response profiles also varied with age. During arrest, juveniles were more likely than adults to emit distress calls and vice-versa for biting and wing flapping during environmental and predator threat. Overall, individualized response profiles were classified into ten clusters that were aligned along two divergent response trajectories when viewed within two-dimensional, multifactorial decision space. Juvenile behaviors tended to follow a predominantly "social-dependence" trajectory, whereas adult behaviors were mostly aligned along a "self-reliance" trajectory. We conclude that bats modify their vocal behavior and make age-appropriate and contextually adaptive decisions when distressed. This decision-making ability is consistent with observations in other social species, including humans.

Interspecific effects of forest fragmentation on bats

Wind-farm development may be an important contributor to forest fragmentation, but how such developments impact bats is poorly understood. We hypothesized that bat activity at a wind farm would be explained, at least in part, by attraction and avoidance behaviours caused by deforestation. We tested predictions of this hypothesis via a landscape-level acoustic, capture, and radiotelemetry survey of little brown bats (Myotis lucifugus (Le Conte, 1831)) and northern long-eared myotis (Myotis septentrionalis (Trouessart, 1897)). Acoustic and capture data indicated no significant difference in magnitude of activity between the fragmented wind farm and the less-fragmented surrounding areas. However, only 2 of 19 radio-tracked bats were ever located inside the wind farm despite being captured adjacent to it. Bat locations were compared against randomly generated locations within the same area in a logistic regression framework to rank landscape variables in order of association with bats. A multicriteria evaluation of forest metrics showed that, over a 3-year period, there was an increase of suitable habitat inside the wind farm for M. lucifugus and a decrease for M. septentrionalis. These results support the contention that, at this level of disturbance, M. lucifugus may use the cleared areas, while M. septentrionalis is negatively impacted by increased deforestation caused by wind-farm development.

The influence of reproductive condition and concurrent environmental factors on torpor and foraging patterns in female big brown bats (Eptesicus fuscus)

Unlike many other mammals, bats in temperate regions employ short bouts of torpor throughout the reproductive period to maintain a positive energy balance. In addition to decreasing energy expenditure during the day, they typically alter foraging patterns as well. It is well known that various environmental conditions influence both torpor and foraging patterns, but studies of these factors often have focussed on one element in isolation thus it is not known how the two behaviours are collectively influencing temperate bats. The objective of our study was to assess how reproductive condition and environmental factors concurrently affect energy balance in female big brown bats (Eptesicus fuscus). We equipped pregnant and lactating bats in southwest Saskatchewan, Canada with temperature-sensitive radio-transmitters. While transmitters were active, skin temperature data were collected and foraging patterns were determined using triangulation. Of the various environmental and physiological parameters used to model torpor characteristics, roost type was the most important factor. Bats roosting in trees used deeper and longer torpor bouts than those roosting in buildings. Lactating bats had a tendency to forage for longer durations than pregnant bats, and often made more foraging trips. When taken together, we found that foraging duration and torpor duration were not directly related during pregnancy, but exhibited an inverse relationship during lactation. This provides support for the hypothesis that there are physiological trade-offs for reproductive bats and suggests that how bats compensate is not entirely predictable based on current environmental conditions.

Movement patterns of an arboreal marsupial at the edge of its range: a case study of the koala

BACKGROUND

Conservation strategies derived from research carried out in one part of the range of a widely distributed species and then uniformly applied over multiple regions risk being ineffective due to regional variations in species-habitat relationships. This is particularly true at the edge of the range where information on animal movements and resource selection is often limited. Here, we investigate home range size, movement patterns and resource selection of koalas Phascolarctos cinereus in the semi-arid and arid landscapes of southwest Queensland, Australia. We placed collars with GPS units on 21 koalas in three biogeographic regions. Home range sizes, resource selection and movement patterns were examined across the three regions.

RESULTS

Habitat selectivity was highest at the more arid, western edge of the koala's range with their occupancy restricted to riparian/drainage line habitats, while the more easterly koalas displayed more variability in habitat use. There was no significant difference between home range sizes of koalas at the western edge of the range compared to the more easterly koalas. Instead, variability in home range size was attributed to spatial variations in habitat quality or the availability of a key resource, with a strong influence of rainfall and the presence of freestanding water on the home range size of koalas. Within a 580 m spatial range, movement patterns of male and female paths showed a tortuous trend, consistent with foraging behavior. Beyond this spatial range, male paths showed a trend to more linear patterns, representing a transition of movement behavior from foraging to breeding and dispersal.

CONCLUSIONS

The difference in home range movement patterns and resource use among the different koala populations shows that behavior changes with proximity to the arid edge of the koala's range. Changes in home range size and resource use near the range edge highlight the importance of further range-edge studies for informing effective koala conservation and management actions, especially when developing species-specific adaptation responses to climate change.

Do predators influence the behaviour of bats?

Many aspects of animal behaviour are affected by real-time changes in the risk of predation. This conclusion holds for virtually all taxa and ecological systems studied, but does it hold for bats? Bats are poorly represented in the literature on anti-predator behaviour, which may reflect a lack of nocturnal predators specialized on bats. If bats actually experience a world with minimal anti-predator concerns, then they will provide a unique contrast within the realm of vertebrate ecology. Alternatively, such predator-driven behaviour in bats may not yet be fully understood, given the difficulties in working with these highly mobile and nocturnal animals. We provide a wide-ranging exploration of these issues in bat behaviour. We first cover the basic predator-prey information available on bats, both on potential predators and the ways in which bats might perceive predators and respond to attacks. We then cover work relevant to key aspects of bat behaviour, such as choice of daytime roosts, the nature of sleep and torpor, evening roost departures, moonlight avoidance, landscape-related movement patterns, and habitat selection. Overall, the evidence in favour of a strong influence of predators on bat behaviour is equivocal, with the picture clouded by contradictory results and a lack of information on potential predators and the perception of risk by bats. It seems clear that day-active bats run a considerable risk of being killed by diurnal raptors, which are able to capture bats with relative ease. Thus, bats taking advantage of a pulse of insects just prior to sunset are likely taking risks to gain much-needed energy. Further, the choice of daytime roosts by bats is probably strongly influenced by roost safety. Few studies, however, have directly addressed either of these topics. As a group, insectivorous temperate-zone bats show no clear tendency to avoid apparently risky situations, such as activity on moonlit nights. However, some observations are consistent with the idea that predation risk affects choice of movement paths and feeding areas by temperate-zone bats, as well as the timing of roost departures. The behaviour of tropical bats, on the other hand, seems more generally influenced by predators; this is especially true for tropical nectarivores and frugivores, but also for insectivorous bats. Presumably there are more serious predators on bats in the tropics (e.g. specialized raptors or carnivorous bats), but the identity of these predators is unclear. More information is needed to assess fully the influence of predators on bat behaviour. There is much need for work on the ways in which bats perceive predators via auditory, visual, and olfactory cues, and whether bats have some knowledge of the risks posed by different predators. Also needed is information on how predators attack bats and how bats react to attacking predators. Difficult to obtain, but of critical value, will be information on the nature of the predation risk experienced by bats while away from roosts and during the full darkness of night.