Geology topics

Corinne A. Diggins

Publications and source records attributed to Corinne A. Diggins.

16 recordsLinked to original sources

USGS2026

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↗

USGS2025

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↗

USGS2022

Seasonal activity patterns of bats in high-elevation conifer sky islands

In the southern Appalachian Mountains of the southeastern USA, bat communities in high-elevation habitats tend to be relatively under-surveyed. High-elevation habitats may provide important habitat to certain species (i.e., migratory tree bats), and may serve as climate refugia during droughts or high temperatures. We conducted an opportunistic acoustic survey of bat communities in ten survey areas in high elevation (1,585–1,920 m a.s.l.) montane Picea rubens (red spruce)- Abies fraseri (Fraser fir) forest in the southern Appalachian Mountains of western North Carolina. In each survey area, we randomly placed three full spectrum acoustic detectors ( N = 30) during three seasons (spring, summer and fall) in 2015. We deployed each detector for two five-day periods during each season ( n = 900 survey nights). Although we detected seven bat species/groups during the surveys, 73% of echolocation files were attributed to Lasiurus cinereus (hoary bat) and Lasionycteris noctivagans (silver-haired bat). Generally rare in the Appalachians and typically present only at low densities in the summer at mid- and low-elevations, both species were detected at all sites during all seasons. Overall, mean nightly activity of bats was higher in the summer than the spring or fall. We observed 3.7–5 times greater activity of L. cinereus in spruce-fir forests during the summer compared to spring and fall, whereas L. noctivagans had 1.3–5 times more activity in the summer compared to other seasons. After accounting for precipitation events, our finite mixture models showed that season, temperature, elevation, and canopy height influenced L. cinereus activity, whereas season and temperature affected L. noctivagans activity. Our observations suggest that high-elevation spruce-fir forests are providing summer foraging and possibly day-roosting habitat of tree bats not previously documented this far south in North America.

North Carolina↗

USGS2022

Distribution probability of the Virginia northern flying squirrel in the High Allegheny Mountains

In the central Appalachians of Virginia and West Virginia, the Virginia northern flying squirrel ( Glaucomys sabrinus fuscus ; VNFS) is a subspecies of northern flying squirrel generally associated with red spruce ( Picea rubens )-dominated forests at high elevations. Listed as endangered by the U.S. Fish and Wildlife Service from 1985 to 2013, the VNFS currently is the subject of a 10-year post-delisting assessment. Still considered a state-listed species in Virginia and a species of greatest conservation need in West Virginia, the VNFS serves as a focal target for red spruce restoration activities in the High Allegheny Region (HAR) of the two states. Owing to the cryptic nature of VNFS and its low detection probability in live-capture surveys, managers in the region rely on habitat models to assess probable presence. Using long-term nest-box, live-trapping, and radio-telemetry data matched with updated high elevation forest-type coverage data for the region, we created a new VNFS resource selection function and spatial coverage map. Inputting red spruce cover, increasing elevation, and decreasing landform index (increasing site shelteredness) composed the best model explaining VNFS occurrence. The calculated amount of low-quality habitat was congruent with previous modeling efforts; however, inclusion of more VNFS occurrence records in the current effort indicated that previous efforts substantially underestimated the amount (>400%) of extant high quality VNFS habitat. We estimate the HAR to contain approximately 197,952 ha with ≥0.50 predicted probability of occurrence of VNFS. In addition to potentially improving current and future VNFS live-capture surveys, with this model managers may better target forests for red spruce restoration to increase high elevation forest ecological integrity and to improve habitat patch connectedness for VNFS.

Maryland, Virginia, West Virginia↗

USGS2021

Spatial behavior of northern flying squirrels in the same social network

North American flying squirrels ( Glaucomys spp.) are social species that communally den and exhibit home range overlap. However, observations on home range overlap tend to come from live-trapped individuals and it is unknown whether overlap occurs among individuals belonging to the same social network. Since flying squirrels communally den with familiar individuals, their use of artificial nest boxes allows for the radio-collaring and tracking of squirrels within the same social network. We captured and radio-collared northern flying squirrels ( G. sabrinus Shaw) found communally denning in nest boxes in the Appalachian Mountains in the eastern United States. We tracked squirrels captured from the same nest box (i.e., nest box groups) to determine home range overlap and subsequent den sharing between familiar individuals within those nest box groups. We found that amount of home range overlap did not differ between male–male, male–female, and female–female dyads, indicating that non-reproductive females and scrotal males are not territorial at the 95% or 50% home range level. Regardless of sex, all dyads had a significantly higher probability of home range overlap (PHR) at the 95% than the 50% home range level (i.e., overlap between squirrels decreases in core areas of their home range). We also found flying squirrels subsequently denned with familiar individuals during 20.9% of occasions post-collaring. Our study provides important information for understanding space use within flying squirrel social networks. Further work should be conducted to determine space use between familiar individuals including seasonal shifts in space use, degree of individual relatedness, and potential territoriality in females denning with young up to and following juvenile dispersal.

Ethology↗

USGS2021

Effects of surveying for the federally endangered Spruce-fir Moss Spider (Microhexura montivaga Crosby & Bishop) on its bryophyte habitat

Microhexura montivaga (Spruce-fir Moss Spider) is a federally endangered arachnid endemic to high-elevation montane conifer forests of the southern Appalachian Mountains. The spider is cryptic and difficult to monitor because this species lives in the interface between the bryophyte mat and the rock surface. Since temporary removal of the bryophyte mat is necessary to monitor the spider, surveyors may negatively impact the spider's habitat during monitoring. To help inform survey protocol for this endangered species, we studied reattachment rates of bryophyte mats to rock surfaces after their removal. In 2017, we surveyed sixty 10 cm × 10 cm plots, assigning a plot to either control or treatment (i.e., application of water post-reattachment). We monitored plots for 1 year post-survey to determine reattachment rates. The majority of plots (70%) reestablished after 1 year, whereas 15% did not reattach or showed substantial prolonged (e.g., ∼1 year) desiccation and 15% completely fell off or had 100% prolonged desiccation and were chlorotic. We found that mat depth and overstory canopy cover had no effect on mat reestablishment, although bryophyte type did. We found no difference between treatment and control plots, suggesting that no treatment is needed for mats to reestablish under the conditions described. Rock slope significantly influenced reestablishment rates, highlighting that surveying bryophyte mats on slopes >80% may diminish or destroy habitat. Further research is needed to determine long-term monitoring effects on the spider and its habitat, especially in relation to disturbance regimes and ecological restoration of Picea rubens (Red Spruce).

Southeastern Naturalist↗

USGS2020

Ultrasonic Acoustic Surveys of State Endangered Northern Flying Squirrels in the Pocono Mountains, Pennsylvania

Surveying for flying squirrels by using traditional techniques produces extremely low detection rates compared with ultrasonic acoustics. Within Pennsylvania, the northern flying squirrel subspecies Glaucomys sabrinus macrotis is state listed as endangered due to habitat loss and parasite-mediated competition by and hybridization with the southern flying squirrel Glaucomys volans . This subspecies is isolated from adjacent populations in West Virginia and New York and has experienced drastic population declines. The discovery and characterization of ultrasonic vocalizations of G. s. macrotis and G. volans , as well as successful field surveys with ultrasonic acoustic detectors in the southern Appalachian Mountains, highlight the potential use of this technique for determining the presence of G. s. macrotis . To confirm the feasibility of using this technique on declining populations of G. s. macrotis sympatric with G. volans , we conducted 108 nights of passive ultrasonic acoustic surveys for G. s. macrotis at six survey sites by using two detectors per survey site ( N = 12 detectors) in June 2017. We considered sites high quality (“high”) or low quality (“low”) based on the number of physical capture records during the past 2 decades and the dominance of boreo-montane conifer tree species in the overstory. We detected G. s. macrotis at four study sites and G. volans at all six study sites. We found higher average probability of detection for G. s. macrotis in high vs. low sites (0.28 ± 0.06 [mean ± SE] and 0.09 ± 0.07, respectively), whereas probability of detection was similar for G. volans between high and low sites (0.13 ± 0.05 and 0.17 ± 0.05, respectively). We also found G. s. macrotis had lower latency of detection at high vs. low sites (2.7 ± 0.8 and 7.83 ± 1.5 nights, respectively) but G. volans did not vary in latency of detection between sites (5 ± 1.6 and 3.8 ± 1.5 nights, respectively). Our study shows acoustics can be successfully used to efficiently survey G. s. macrotis in Pennsylvania, where populations are small and monitoring these populations more effectively is critical to determining changes in persistence due to climate- and disease-induced factors.

Pennsylvania↗

USGS2020

Using ultrasonic acoustics to detect cryptic flying squirrels: Effects of season and habitat suitability

New technologies allow for more efficient and effective monitoring of rare or elusive species. However, standardizing protocol to ensure high detection rates is important prior to widespread use of a new technique. The use of ultrasonic acoustic detectors to survey for flying squirrels ( Glaucomys spp.) is a novel method that is more efficient than traditional methods. However, certain methodologies for this technique still need to be refined. During 2015, we conducted a seasonal and habitat quality study on the endangered Carolina northern flying squirrel ( G. sabrinus coloratus ) in western North Carolina, USA. Our seasonal study examined differences in probability of detection (POD) and latency to detection (LTD) at 30 high-quality sites across 10 survey nights in spring, summer, and autumn. The habitat quality study focused on POD and LTD among 15 sites with varying habitat quality (5 High, 5 Medium, 5 Low) across 20 survey nights. We found POD similar between seasons, with POD 15–20% greater during spring. The LTD was comparable among seasons. We found that POD and LTD varied at sites with different habitat quality. The POD was similar between High and Medium sites (0.26 ± 0.04 SE and 0.29 ± 0.05, respectively), but greater than Low sites (0.02 ± 0.02). The LTD was not different among sites with differing habitat quality, although LTD at High sites was 2.7 and 4.5 times lower than Medium and Low sites, respectively. Trill calls, the most distinctive species-specific call type produced by species of flying squirrels, was recorded at greater rates in spring versus other times of the year. Our results indicate flying squirrels can be surveyed during any season, although habitat quality needs to be considered when determining survey length. For Carolina northern flying squirrel, the optimal time to perform acoustic surveys is during the spring season for 6–10 survey nights at sites with high or medium habitat quality.

North Carolina↗

USGS2020

Hypogeous, sequestrate fungi (genus Elaphomyces) found at small-mammal foraging sites in high-elevation conifer forests of West Virginia

Little is known about hypogeous, sequestrate (i.e., truffles) fungi in the eastern United States. Since the fruiting bodies of these fungi are part of the diet of multiple rodent species, filling data gaps is important to understanding more about truffle species distribution and habitat associations. During a microhabitat study on radio-collared Virginia Northern Flying Squirrels (Glaucomys sabrinus fuscus Miller) in 2013, we opportunistically sampled truffles at small mammal digs and scratches within our microhabitat plots. All sampling was conducted within known squirrel foraging home ranges. We found three Elaphomyces species: Elaphomyces macrosporus Castellano and Elliott, E. verruculosus Castellano, and E. americanum Castellano. Our observations of E. macroporus are the first from West Virginia. Herein, we describe the microhabitat associations for each fungal species. We suggest using small mammal digs and scratches as potential indicators to opportunistically gather more information on truffle species in coniferous forests of the eastern United States.

West Virginia↗

USGS2019

Activity patterns and temporal predator avoidance of white-tailed deer (Odocoileus virginianus) during the fawning season

In the presence of a predator, prey may alter their temporal activity patterns to reduce the risk of an encounter that may induce injury or death. Prey perception of predation risk and antipredator responses may increase in the presence of dependent offspring. We conducted a camera trap study during summer 2015 in North Carolina and Tennessee, USA to evaluate temporal avoidance of a predator (coyote Canis latrans ) by white-tailed deer ( Odocoileus virginianus ). We analyzed activity patterns of bucks, does, and nursery groups (i.e., groups that included fawns) relative to those of coyotes to determine the coefficient of overlap (Δ) using a kernel density estimator. We found that bucks and does had similar Δ with coyotes [Δ 1 = 0.729 (0.629–0.890) and Δ 1 = 0.686 (0.558–0.816, respectively] and exhibited crepuscular activity patterns comparable to those of coyotes. However, nursery groups displayed a dramatically different activity pattern: unimodal activity was concentrated in the middle of the day with little overlap with coyote activity [Δ 1 = 0.362 (0.176–0.491)]. Because adult deer are rarely prey for coyotes, whereas fawns are common prey during summer, the shift in activity patterns of nursery groups demonstrates a behavioral shift likely aimed at avoiding coyote predation on fawns.

North Carolina, Tennessee↗

USGS2017

Microhabitat selection of the Virginia Northern Flying Squirrel (Glaucomys sabrinus fuscus Miller) in the central Appalachians

Glaucomys sabrinus fuscus (Virginia Northern Flying Squirrel; VNFS) is a rare Sciurid that occurrs in the Allegheny Mountains of eastern West Virginia and northwest Virginia. Previous work on this subspecies has confirmed close associations with Picea rubens (Red Spruce) at the landscape and stand levels in the region. However, ongoing Red Spruce restoration actions using canopy-gap creation to release single or small groups of trees requires a better understanding of within-stand habitat selection of VNFS to assess potential short- and medium-term impacts. To address these questions, we conducted a microhabitat study using radio-collared squirrels in montane conifer and mixed conifer—hardwood stands. We used points obtained from telemetry surveys and randomly generated points within each squirrel's home range to compare microhabitat variables for 13 individuals. We found that VNFS preferentially selected plots with conifer-dominant overstories and deep organic-soil horizons. VNFS avoided plots with dense Red Spruce regeneration in the understory in stands with hardwood-dominated overstories—the types of areas targeted for Red Spruce restoration. We also opportunistically searched for hypogeal fungi at telemetry points and found 3 species of Elaphomyces during our surveys. Our results indicate that microhabitat selection is associated with Red Spruce-dominant forests. Efforts to restore Red Spruce where hardwoods dominate in the central Appalachians may improve the connectivity and extent of habitat of VNFS.

West Virginia↗

USGS2017

Home range, den selection and habitat use of Carolina northern flying squirrels (Glaucomys sabrinus coloratus)

Context: Understanding habitat selection is important for determining conservation and management strategies for endangered species. The Carolina northern flying squirrel (CNFS; Glaucomys sabrinus coloratus ) is an endangered subspecies found in the high-elevation montane forests of the southern Appalachians, USA. The primary use of nest boxes to monitor CNFS has provided biased information on habitat use for this subspecies, as nest boxes are typically placed in suitable denning habitat. Aims: We conducted a radio-telemetry study on CNFS to determine home range, den site selection and habitat use at multiple spatial scales. Methods: We radio-collared 21 CNFS in 2012 and 2014–15. We tracked squirrels to diurnal den sites and during night-time activity. Key results: The MCP (minimum convex polygon) home range at 95% for males was 5.2 ± 1.2 ha and for females was 4.0 ± 0.7. The BRB (biased random bridge) home range at 95% for males was 10.8 ± 3.8 ha and for females was 8.3 ± 2.1. Den site ( n = 81) selection occurred more frequently in montane conifer dominate forests (81.4%) vs northern hardwood forests or conifer–northern hardwood forests (9.9% and 8.7%, respectively). We assessed habitat selection using Euclidean distance-based analysis at the 2nd order and 3rd order scale. We found that squirrels were non-randomly selecting for habitat at both 2nd and 3rd order scales. Conclusions: At both spatial scales, CNFS preferentially selected for montane conifer forests more than expected based on availability on the landscape. Squirrels selected neither for nor against northern hardwood forests, regardless of availability on the landscape. Additionally, CNFS denned in montane conifer forests more than other habitat types. Implications: Our results highlight the importance of montane conifer to CNFS in the southern Appalachians. Management and restoration activities that increase the quality, connectivity and extent of this naturally rare forest type may be important for long-term conservation of this subspecies, especially with the impending threat of anthropogenic climate change.

Appalachian Mountains↗

USGS2017

High-elevation observations of Long-tailed Weasel and Eastern Chipmunk in North Carolina

Observations of Mustela frenata (Long-tailed Weasel) are rare within the southern Appalachians, while observations of Tamias striatus (Eastern Chipmunk) are uncommon in high-elevation spruce-fir forests. We conducted camera-trap surveys at Roan Mountain Highlands, Mitchell County, NC, during summer 2016 in a Picea rubens (Red Spruce)— Abies fraseri (Fraser Fir) forest. During the survey, we observed a Long-tailed Weasel at 1893 m in elevation and an Eastern Chipmunk at 1703 m in elevation. These are the highest-elevation records for both species in the eastern United States outside of Great Smoky Mountains National Park, and the highest elevation record for Longtailed Weasel in North Carolina.

North Carolina↗

USGS2016

Predictive habitat models derived from nest-box occupancy for the endangered Carolina northern flying squirrel in the southern Appalachians

In the southern Appalachians, artificial nest-boxes are used to survey for the endangered Carolina northern flying squirrel (CNFS; Glaucomys sabrinus coloratus ), a disjunct subspecies associated with high elevation (>1385 m) forests. Using environmental parameters diagnostic of squirrel habitat, we created 35 a priori occupancy models in the program PRESENCE for boxes surveyed in western North Carolina, 1996-2011. Our best approximating model showed CNFS denning associated with sheltered landforms and montane conifers, primarily red spruce Picea rubens . As sheltering decreased, decreasing distance to conifers was important. Area with a high probability (>0.5) of occupancy was distributed over 18662 ha of habitat, mostly across 10 mountain ranges. Because nest-box surveys underrepresented areas >1750 m and CNFS forage in conifers, we combined areas of high occupancy with conifer GIS coverages to create an additional distribution model of likely habitat. Regionally, above 1385 m, we determined that 31795 ha could be occupied by CNFS. Known occupied patches ranged from

North Carolina, Tennessee, Virginia↗

USGS2016

Release of suppressed red spruce using canopy gap creation—Ecological restoration in the Central Appalachians

Red spruce ( Picea rubens ) and red spruce-northern hardwood mixed stands once covered as much as 300,000 ha in the Central Appalachians, but now comprise no more than 21,000 ha. Recently, interest in restoration of this forest type has increased because red spruce forests provide habitat for a number of rare animal species. Our study reports the results of an understory red spruce release experiment in hardwood-dominated stands that have a small component of understory red spruce. In 2005, 188 target spruce were identified in sample plots at six locations in central West Virginia. We projected a vertical cylinder above the crown of all target spruces, and in 2007, we performed a release treatment whereby overtopping hardwoods were treated with herbicide using a stem injection technique. Release treatments removed 0–10% (Control), 11–50% (Low), 51–89% (Medium), and ≤90% (High) of the basal area of overtopping trees. We also took canopy photographs at the time of each remeasurement in 2007, 2010, and 2013, and compared basal removal treatments and resulting 2010 canopy openness and understory light values. The high treatment level provided significantly greater six-year dbh and height growth than the other treatment levels. Based on these results, we propose that a tree-centered release approach utilizing small canopy gaps that emulate the historical, gap-phase disturbance regime provides a good strategy for red spruce restoration in hardwood forests where overstory spruce are virtually absent, and where red spruce is largely relegated to the understory.

Natural Areas Journal↗

USGS2015

Atypical den use of Carolina Northern Flying Squirrels ( Glaucomys sabrinus coloratus ) in the southern Appalachian Mountains

Glaucomys sabrinus coloratus (Carolina Northern Flying Squirrel) is a federally endangered subspecies that occurs in high elevation forests of the southern Appalachian Mountains. Denning sites may be a limiting factor for this subspecies in areas where cavity trees are not abundant or where interspecific competition from other tree squirrels occurs. This shortage can result in use of unusual denning sites, such as subterranean dens. Herein, we report atypical denning habits of radio-collared Carolina Northern Flying Squirrels in southwestern Virginia and western North Carolina from 2008 to 2011 and 2014. Increased knowledge of denning habitats may be beneficial for conservation and habitat management of this subspecies, particularly in sub-optimal or degraded habitats.

North Carolina↗