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W. Mark Ford

Publications and source records attributed to W. Mark Ford.

At least 19 recordsLinked to original sources

Comparison of data handling techniques for modeling bat acoustic activity

With the proliferation of acoustic sampling to investigate bat distribution and ecology, researchers have implemented a myriad of statistical modeling approaches to interpret findings. Bats are taxa of high conservation concern; therefore, ensuring the accuracy of species-level habitat association models is critical for informing management. We sought to determine prediction differences among statistical approaches to modeling counts of acoustic detections, using generalized linear mixed models with 8 acoustic data-handling techniques. We applied each approach or combination of approaches to a rare species, the northern long-eared bat ( Myotis septentrionalis ), and a common species, the eastern red bat ( Lasiurus borealis ), from summer survey results on a landscape in south-central Pennsylvania, USA, 2024. We evaluated the accuracy of habitat association models of bat acoustic activity at the species level using cross-validation and compared resulting predictions of models using spatial correlations. We determined that filtering data by automated identification software (Kaleidoscope Pro), the maximum likelihood estimate (MLE) P -value thresholds reduced relative mean absolute error (rMAE) in cross-validation of northern long-eared bat models. Using the MLE-retained data produced the most accurate predictions over using raw data or the overly conservative match ratio data. However, for the eastern red bat, the results from the most conservative approach of only retaining data with at least a 90% match ratio from software development training sets had the lowest rMAE. We have provided evidence that the current standard of filtering data by nightly MLE can result in more accurate and informative habitat-use acoustic activity models for rare bat species.

Pennsylvania

Exploratory ecology of reintroduced elk in Virginia

Reintroductions of extirpated species are an important tool in wildlife conservation. Understanding how reintroduced populations acclimatize to novel environments can lend insight into social learning that in turn is valuable for assessing reintroduction success and maximizing efficacy of subsequent efforts. During 2012, 2013, and 2014, the Virginia Department of Wildlife Resources implemented soft releases of elk ( Cervus canadensis ) translocated to southwestern Virginia from eastern Kentucky. We investigated home range establishment and post-release movements of these reintroduced elk ( n = 60). We found adults moved farther from the release site than either yearlings or calves (F = 6.93, p = 0.001). Elk released in 2012 and 2013 took similar amounts of time to establish home ranges (median 181 days, range 108–214 days; and median 189 days, range 147–209 days, respectively), but individuals released in 2013 remained closer to the release site ( 𝑥 ̲ = 605.5 m, SD = 335.7 m, closer) presumably by joining established social groups. However, the 2014 cohort generally took longer to establish home ranges (median: 231 days; range: 56–258 days) and moved farthest from the release site ( 𝑥 ̲ = 1360.2 m, SD = 293.9 m, farther than 2012 individuals) possibly due to the larger cohort size and resulting intraspecific competition, or the earlier release date that year. Our findings suggest the number of consecutively released cohorts, the timing of the release, and the composition of age classes for released individuals are important considerations for reintroductions.

Virginia

Resource selection for an endangered flying squirrel, Glaucomys sabrinus coloratus, in a montane sky-island system

Geographically isolated endemic species and their habitats in montane systems face stressors of rapid climate change as well as legacy and contemporary land use change. In the case of endangered species in fragmented terrestrial montane habitats, effectively sky-islands, insight into habitat use and resource selection is vital for effective conservation measures. We created a resource selection function using a long-term dataset of multiple monitoring techniques (live-trapping, radio-telemetry, camera traps, acoustic detectors, and nest boxes) across a wide geographical range for an endangered subspecies, the Carolina northern flying squirrel Glaucomys sabrinus coloratus , in a vulnerable high-elevation sky-island boreal forest ecosystem in the southeastern USA. Using fine-scale habitat and topographic coverage on 8 sky-islands, we employed various models to capture nuanced habitat relationships that can better inform the conservation of remaining subpopulations as well as other endemic species that share their habitat. Our analyses confirmed that red spruce Picea rubens -Fraser fir Abies fraseri was the most significant habitat component for determining Carolina northern flying squirrel presence, but that relationships varied somewhat among sky-islands owing to differences in extent, elevation range, and forest community configurations. Further, we found that solely using nest boxes, as previously reported, to create a resource selection function biased the results, but that nest boxes remain an effective tool for overcoming habitat fragmentation and decreasing exposure to antagonistic species.

North Carolina, Tennessee, Virginia

Multiscale resource selection for a reintroduced elk population

Patterns of resource selection are driven by the decision-making processes of animals occurring at multiple scales from where to establish a home range (i.e., second order selection) to which resource patches to use within the home range (i.e., third order selection). Elk ( Cervus canadensis ) were reintroduced to southwestern Virginia, USA, from 2012 to 2014 following successful translocations onto reclaimed surface coal mines in the region. We sought to understand how elk have acclimated following their translocation using location data from GPS-collared adult female elk ( n = 33) collected from 2019 to 2022 along with remotely sensed terrain and land cover data. We utilized continuous-time movement models paired with generalized linear mixed-effects modeling to describe seasonal resource selection at second and third orders. At both scales of selection and throughout the year, female elk selected reclaimed surface mines, conifer forests, ridgetops, and areas with lower terrain roughness, while avoiding mixed hardwood and oak ( Quercus spp.) forests. Unmined open land was only selected at the third order during periods of forage scarcity (i.e., winter) and increased metabolic requirements (i.e., late gestation). Although surface coal mining leaves legacy environmental impacts on the landscape, management of these sites provides benefits to elk and maintains open habitat that is otherwise limited.

Virginia

Boxed in or branching out? Movement and resource selection of eastern box turtles (Terrapene carolina carolina) in an urban green space

The eastern box turtle ( Terrapene carolina carolina ) is a long-lived terrestrial turtle species distributed throughout the eastern United States that has experienced widespread population decline. Many eastern box turtle populations are persisting as remanent populations in small, fragmented urban green spaces. We investigated the movement and resource selection of eastern box turtles within a mid-Atlantic region urban forest in the eastern United States. We used a combination of turtle occurrence data (via visual encounter surveys) and radio telemetry to create resource selection functions. Additionally, we applied a simulation modeling approach and modeled activity areas via dynamic Brownian Bridge Movement Models to quantify interactions between turtles and roads or trails. We also used these models to determine the propensity for turtles to move outside of the managed urban forest boundary and into surrounding development. We observed that turtles selected for deciduous forest patches and avoided roads and trails despite the urban forest having very little available areas where anthropogenic features could be avoided. We also demonstrated observed (and probable) movements outside of the urban forest boundary. Although eastern box turtles are persisting within the urban green space we examined, our work determined that interactions with roads and trails, and movements outside of protected boundaries into developed areas present challenges to individuals navigating the urban forest.

eastern United States, mid-Atlantic region

Interacting effects of human presence and landscape modification on birds and mammals

Sustainable human–wildlife coexistence requires a mechanistic understanding of the many ways that humans affect animals. However, progress is hampered by the lack of accessible data measuring the dynamic presence of people. Here, we leverage mobile-device data to disentangle how human presence and landscape modification differentially influence the use of geographic and environmental space for 37 mammal and bird species across the United States. Human presence affected more than 65% of species, with substantial variation across species. For ~60% of species that responded to human activities, the effects were interdependent—animals tended to react more strongly to human presence in less modified habitats. Our results demonstrate that human presence and landscape modification have complex combined effects on wildlife, which need to be considered for effective management.

Science

Relative activity of three bat species Impacted by white-nose syndrome on the Chesapeake and Ohio Canal National Historical Park

White-nose syndrome, a disease caused by the fungal-pathogen Pseudogymnoascus destructans , has caused drastic reductions in populations of several North American hibernating species of bats including Myotis lucifugus (Little Brown Bat), Myotis septentrionalis (Northern Long-eared Bat), and Perimyotis subflavus (Tricolored Bat). Recent data indicate that populations of Little Brown Bats may be stabilizing and/or increasing in the northeastern region of the US, while others, such as Northern Long-eared Bats, continue to decline. Whether these trends extend to the mid-Atlantic region is currently unknown. To better understand population changes over time, habitat associations, and species dynamics, we developed models of relative activity from bat acoustic data collected on the National Park Service's Chesapeake and Ohio Canal National Historical Park along the Potomac River Corridor in western Maryland between 2016 and 2022. Consistent with pre-disease habitat associations, Little Brown Bats and Tricolored Bats exhibited a positive correlation with proximity to water bodies. Notably, we found Little Brown Bat and Tricolored Bat populations potentially were increasing, whereas Northern Long-eared Bats showed no correlation with examined habitat covariates and had low detection levels, trends consistent with broader declines throughout their range.

Maryland

Spatial occupancy patterns of the endangered northern long‐eared bat in New England

Aim White-nose syndrome has caused severe declines in eastern North American cave bats, leading to the federal listing of the northern long-eared bat ( Myotis septentrionalis ) as endangered in the United States and Canada. This has heightened the importance of long-term monitoring to inform species status assessments. We employed a combination of long-term repeated and single-season acoustic survey data to assess the regional presence, spatial distribution, occupancy, and detection probability of northern long-eared bats. Location New England, United States. Methods We analysed acoustic data from 2357 detector sites, aggregated by year, using Bayesian single-species occupancy models. We investigated the influence of habitat characteristics, climatic variables, and year (2015–2022) on occupancy and the effects of weather conditions and survey month (May to August) on detection probability. Spatial random effects were included to address residual spatial autocorrelation, with a 1-km resolution chosen based on significant positive autocorrelation observed in a non-spatial model. Results Occupancy was highest on steep, forested hillsides with minimal anthropogenic development, higher in warmer regions, particularly along coastlines and on offshore islands, and declined across survey years. Including a 1-km spatial random effect reduced residual autocorrelation and suggests northern long-eared bats utilise resources at small to medium landscape scales. Detection probability was highest earlier in the maternity season, but declined when monthly precipitation or temperature exceeded average conditions. Conclusions Conservation efforts that focus on steep, forested hillsides in warmer regions with low anthropogenic development could be beneficial. Our analysis supports the use of spatial random effects at a 1-km 2 scale, highlighting the importance of survey designs that capture ecological variation at species-specific resolutions. Additionally, early-season acoustic surveys conducted during favourable weather conditions may improve monitoring effectiveness. Acoustic sampling and spatial occupancy modelling offer powerful tools for monitoring remnant populations of northern long-eared bats and guiding conservation practices.

Connecticut, Maine, Massachusetts, New Hampshire,

Red spruce forest stand structure and Virginia northern flying squirrel habitat suitability

The Virginia northern flying squirrel ( Glaucomys sabrinus fuscus ; VNFS) is a rare, Pleistocene-relict, disjunct subspecies of the northern flying squirrel. The squirrel occurs only in high-elevation red spruce ( Picea rubens ) forests of the central Appalachian Mountains of Virginia and West Virginia—a forest type that was substantially reduced by exploitative logging and wildfire in the 1890s–1930. Owing to its cryptic nature and difficulty of capture, managers have relied on an evolving series of predicted habitat suitability models that primarily have used topographic measures and red spruce cover class to assess potential occupancy on the landscape. Currently, VNFS is considered the sentinel species in the region whereby its predicted presence indicates red spruce forests with higher relative habitat integrity, and unsuitable habitat highlights where red spruce restoration or enhancement should occur. However, extant VNFS models only use red spruce percent composition and do not provide insights into forest structure, such as forest canopy height or basal area, that are needed by managers to implement restoration or assess effectiveness. We examined recent historical VNFS observations from nest-box surveys and radiotelemetry data (natural dens and foraging points) relative to random pseudoabsence points across red spruce cover classes from the most current VNFS predicted probability habitat model. Using generalized linear models in an information-theoretic approach, we found that within each red spruce composition class, suitable VNFS habitat was related to increased forest canopy height (m), basal area (m 2 ·ha −1 ), quadratic mean diameter (cm), and stem density (number of trees ha −1 ), indicating that, within red spruce and mixed red spruce–northern hardwood forests, VNFS is associated most with mature forest conditions. Accordingly, our results could be recombined with habitat suitability models to prioritize where, for example, red spruce forest structural enhancement would facilitate shifting a given stand to a higher probability condition for VNFS use.

Maryland, Virginia, West Virginia

The bat signal: An ultraviolet light lure to increase acoustic detection of bats

Bats are a taxa of high conservation concern and are facing numerous threats including widespread mortality due to White-Nose Syndrome (WNS) in North America. With this decline comes increasing difficulty in monitoring imperiled bat species due to lower detection probabilities of both mist-netting and acoustic surveys. Lure technology shows promise to increase detection while decreasing sampling effort; however, to date research has primarily focused on increasing physical captures during mist-net surveys using sound lures. Because much bat monitoring is now performed using acoustic detection, there is a similar need to increase detection probabilities during acoustic surveys. Ultraviolet (UV) lights anecdotally have been shown to attract insects and thereby attract foraging bats for observational studies and to experimentally provide a food source for WNS-impacted bats before and after hibernation. Therefore, we constructed a field-portable and programmable UV lure device to determine the value of lures for increasing acoustic detection of bats. We tested if the lure device increased both the echolocation passes and feeding activity (feeding buzzes) across a transect of bat detectors. There was an increase in feeding activity around the UV light, with a nuanced, species-specific and positionally dependent effect on echolocation passes received. The UV light lure increased echolocation passes for the eastern red bat ( Lasiurus borealis ), little brown bat ( Myotis lucifugus ), and evening bat ( Nycticeius humeralis ), but decreased passes of the North American hoary bat ( Lasiurus cinereus ). The northern long-eared bat ( Myotis septentrionalis ) showed a negative response within the illuminated area but increased echolocation activity outside the illuminated area during lure treatment and activity was elevated at all positions after the lure was deactivated. Our study demonstrates some potential utility of UV lures in increasing the feeding activity and acoustic detection of bats. Additional research and development of UV lure technology may be beneficial, including alternating on and off periods to improve detection of light-averse species, and improving echolocation call quality along with the increase in received passes.

Virginia

Resource selection of the southern fox squirrel (Sciurus niger niger) in the coastal plain of Virginia

The southern fox squirrel ( Sciurus niger niger ) is a subspecies of fox squirrel that ranges from southeastern Virginia to northern Florida. Throughout its Southeastern range, southern fox squirrel habitat of natural mixed pine-hardwood forests has been fragmented by agriculture and short-rotation pine plantations. In Virginia, remaining habitat has been transformed by fire suppression on the landscape and has in turn resulted in small, disjunct populations of southern fox squirrels. We sought to identify the home range and resource utilization of southern fox squirrels in the southern Coastal Plain of Virginia. From established nest boxes, we captured, radio collared and tracked four individuals at Big Woods Wildlife Management area and Piney Grove Complex in Sussex County in 2022. We observed an average male 95% and 50% adaptive kernel home range 173.49 ha (SE = 25.73, N = 2) and 40.62 ha (SE = 5.87, N = 2), respectively and an average female 95% and 50% adaptive kernel home range of 28.51 ha (SE = 0.49, N = 2) and 4.71 ha (SE = 0.34, N = 2), respectively. At both the second and third orders of habitat selection, squirrels selected for pine savanna cover types and short fire-return intervals.

Virginia

Acoustic response of bats to the Brood X Periodical Cicada (Magicicada spp.) emergence

Periodical cicada emergences can positively affect vertebrate reproduction and breeding behavior, yet this response is not well studied for bats. We examined the acoustic response of 6 species/phonic groups of bats in 2021 to the emergence of Brood X periodical cicadas, along the Potomac River corridor, in Maryland and Virginia. Using a before-after-control-impact study design, we deployed ultrasonic acoustic detectors during the summers of 2020–2022 within and just outside the range of the cicada emergence to document bat response. We observed significantly more echolocation passes during the 2021 emergence and the year following within the range of cicadas, relative to changes among years outside of the periodical cicada range. Our study demonstrates that periodical cicadas may serve as a resource that causes an increase in bat activity.

Maryland, Virginia, West Virginia

Disentangling genetic diversity of Myotis septentrionalis: population structure, demographic history, and effective population size

Myotis septentrionalis (Northern Long-eared Bat) has recently suffered a >90% decline in population size in North America due to white-nose syndrome (WNS). We assessed genetic diversity, population structure, current effective population size, and demographic history of M. septentrionalis distributed across the United States to determine baseline levels pre-WNS. We analyzed RADseq data from 81 individuals from Kentucky, Louisiana, Michigan, Minnesota, North Carolina, Oklahoma, and Wisconsin. Additionally, we examined population genetic structure using discriminant analysis of principal components, fastStructure, and STRUCTURE. We then estimated effective population size and demographic history using fastsimcoal2. Similar levels of genetic diversity were found across all samples. We found no population genetic structure in the varied analyses from these contemporary samples. The best model for demographic history estimated a rapid population expansion followed by a slower expansion approximately 340,000 years ago. The vagility of M. septentrionalis , along with male dispersal and random mating, may provide a buffer against serious bottleneck effects stemming from rapid population declines due to WNS. This research provides a baseline for tracking and monitoring the influence of WNS on genetic diversity such as potential reduced diversity or increased population structuring in the future.

Kentucky, Louisiana, Michigan, Minnesota, North Ca

Second guessing the maximum likelihood estimator values for bat surveys

T The U.S. Fish and Wildlife Service allows acoustical surveys and automated identification software to determine the presence of the endangered northern long-eared bat ( Myotis septentrionalis ) and Indiana bat ( Myotis sodalis ). Analytical software is required to assess presence probability on a site-night basis using a maximum likelihood estimator (MLE) that accounts for interspecific bat misclassification rates. The current standard for occupancy is a returned MLE P-value < 0.05 at the nightly level irrespective of the number of files identified as either northern long-eared bats or Indiana bats. These MLE P-values can vary based on presence of other bat species with similar calls and the relative proportions of all species recorded. Accordingly, there is concern that with few nightly northern long-eared bat or Indiana bat recordings or the presence of large numbers of high-frequency bats, false-negative findings from a swamping effect could result. Using data collected in 2020–2021 by the U.S. Fish and Wildlife Service to set nationwide acoustic monitoring guidelines, we examined the relationship of returned software MLE P-values from 4873 site-nights of acoustic detector data relative to nightly counts of northern long-eared bats and Indiana bats, overall counts of other high-frequency bats, and habitat cover type. For both northern long-eared bats and Indiana bats, nights with one or more echolocation pass files identified as either species but above the MLE P-value threshold largely occurred where nightly counts of the target species was <15 and their proportion to the count of high-frequency bat species was low. We followed this analysis with a simulation using a known call library and observed similar patterns. Accordingly, with few nightly cholocation passes, post-hoc visual assessment following automated software identification easily could be undertaken. Evidence of swamping by other high-frequency species causing positive file identification creating false-negative or false-positives of northern long-eared bats and Indiana bats was not apparent at nightly counts of either species > 10.

Alabama, Arkansas, Illinoise, Indiana, Kentucky, M

Home range size and resource use by eastern spotted skunks in Virginia

Throughout much of the eastern U.S., many forested ecosystems have lost large amounts of core forest areas due to land-use change, isolating wildlife in forest fragments. The eastern spotted skunk ( Spilogale putorius ) is considered a species of conservation concern in Virginia, where populations are restricted to spatially disjunct forest patches in the central Appalachian Mountains. We caught and radio-tagged eastern spotted skunks in the Appalachian Mountains of Virginia to assess whether current habitat fragmentation restricts skunk movements and hence distribution, potentially leading to isolation among habitat patches. Denning home range size (approximately 3.7 km 2 ) in our study was smaller than those in other studies of eastern spotted skunks and excursive movements were primarily limited to core forested areas (>2 km 2 ). Core forested areas were used more than non-forested and forest-edge areas. We conclude core forest area fragmentation limits eastern spotted skunk movement between mountain ridges. Increased forest patch connectivity may help prevent genetic and demographic isolation, reduce the likelihood of local extinctions, and facilitate colonization of suitable unoccupied areas.

Virginia

Seasonal activity patterns of northern long-eared bats on the coastal Mid-Atlantic

Conservation of bats declining from white-nose syndrome (WNS) impacts requires an understanding of both temporal and landscape-level habitat relationships. Traditionally, much of the research on bat ecology has focused on behavior of summer maternity colonies within species’ distribution cores, including that of the endangered northern long-eared bat ( Myotis septentrionalis ). To further our knowledge of this species, we evaluated multi-season activity patterns in eastern North Carolina and Virginia, including areas where populations were recently discovered. We used passive acoustic monitoring to assess relative and probable activity of northern long-eared bats from October 2016 to August 2021. Northern long-eared bat relative activity was greatest in areas containing greater proportions of woody wetlands and upland pine-dominated evergreen forests. However, the likelihood of recording northern long-eared bats was associated with smaller proportions of woody wetlands and open water resources. Furthermore, we observed a higher probability of recording northern long-eared bats during non-winter seasons. Probable activity was greatest at temperatures between 10 and 25 C, potentially highlighting an optimal thermoneutral zone for the species regionally. Relative activity of northern long-eared bats on the Coastal Plain of Virginia and North Carolina was primarily driven by cover features, whereas probable activity was driven by a combination of cover features, seasonality, and temperature. Therefore, acoustical surveys for this species may be most effective when targeting woody wetlands adjacent to upland forests, particularly upland pine-dominated evergreen stands, during moderate temperatures of non-winter seasons (1 April–15 November). Moreover, conservation of a diverse mosaic of woody wetlands juxtaposed by upland forests may promote both roosting and overwintering habitat, thereby enhancing overwintering survival, maternity colony establishment, and ultimately, successful reproduction of northern long-eared bats.

North Carolina, Virginia

Seasonal activity patterns of northern long-eared bats at hibernacula in western Virginia

Understanding the relationships of biotic and abiotic factors to seasonal activity at hibernacula is important for the conservation of bats impacted by white-nose syndrome (WNS). Research on the relative and probable activity patterns of the federally endangered northern long-eared bat ( Myotis septentrionalis ) primarily has focused on summer maternity colonies, whereas surveys at hibernacula have traditionally relied on external capture and internal counts. We used passive acoustic monitoring to assess the relative and probable activity of northern long-eared bats at 13 hibernacula in western Virginia, from August 2020 to May 2022. Northern long-eared bats were most active near hibernacula during warmer weeks of the fall swarm and spring emergence, when rainfall was low. Similarly, the probability of northern long-eared bat activity was highest near hibernacula during the spring/summer season. However, unlike relative activity, the likelihood of recording northern long-eared bats was associated with more heterogeneous, interior forests. Our results suggest that northern long-eared bat activity largely follows the described pre-WNS hibernation phenology of the species. Therefore, acoustical surveys to monitor northern long-eared bat populations at hibernacula should focus on entrances during peak activity periods (mid-April and early September), rather than the nearby landscape. Finally, management to promote resource-rich foraging habitat adjacent to hibernacula for use during swarming and emergence may increase survival during hibernation, fitness for spring migration, and ultimately, improve the reproductive success of northern long-eared bats in western Virginia.

Virginia

Reproductive trends in Little Brown Bats before and after the onset of white-nose syndrome in Virginia

Myotis lucifugus (Little Brown Bat) declines in Virginia following white-nose syndrome (WNS) prompted an investigation into reproductive behaviors of surviving individuals. To examine reproductive change, we examined female bats prior to, during and after endemism establishment. We also examined capture trends of juveniles at maternity colonies. Timing and proportion of reproductive conditions did not differ except for reductions in lactating females during WNS invasion relative to the pre-WNS period. There was no significant difference in the proportion of juveniles between WNS-endemic years, indicating population recovery is slow. Of 78 recaptures, 2 individuals survived >8 years, suggesting individual longevity after WNS endemism. Our findings emphasize the value of long-term datasets to assess reproductive status of Little Brown Bats.

Virginia