Den Habitat Research Articles

Assessing past and future climatic influences on the availability of polar bear maternal denning habitat on Wrangel Island

Long-term changes in environmental conditions resulting from climate change may negatively affect reproductive success and lead to population-level consequences for species, especially those living at higher latitudes. Throughout their range, female polar bears (Ursus maritimus) typically require snowdrifts, either on the ice or land, to excavate maternal dens. In the Chukchi Sea (CS) subpopulation, 84% of dens have been reported to on land and 68% of these on Wrangel Island, Russia. Therefore, availability of suitable den habitat on Wrangel Island is critical for the long-term persistence of the CS subpopulation. We performed a retrospective analysis (1980–2020) of the availability of snowdrifts on Wrangel Island to estimate how the timing and distribution of snowdrifts suitable for denning has changed over this period. We evaluated the spatial distribution and availability of potential denning habitat across Wrangel Island from 1 September until 15 December and documented changes in snow conditions through time. We used sensitivity simulations under variable temperature increases associated with climate change projections to predict how availability of potential denning habitat on Wrangel Island might change in the future. We found no trends in spatial or temporal availability of modeled den habitat over the past 41 years. A projected 7.6 °C rise in temperature relative to current conditions resulted in a ∼50% reduction of denning habitat. If temperatures increase ≥13.6 °C relative to current conditions, 100% of denning habitat would be lost. Despite rising temperatures and sea ice loss, the climate of this area is cold enough that availability of denning habitat is not an immediate limiting factor for the CS subpopulation.

A review of progress of a research program for the endangered northern quoll (Dasyurus hallucatus) in the multi-use landscapes of the Pilbara

Maximising conservation outcomes for threatened species in multi-use landscapes is likely to require a multi-stakeholder, coordinated approach that is tenure blind. Here, we conduct a review of a research program targeting the endangered northern quoll (Dasyurus hallucatus) in the Pilbara region of Western Australia; an area with a high concentration of mining and pastoral activities. To inform ongoing investment to support northern quoll conservation, we identify future directions that either add value to research already undertaken or are based on the original priorities that have not been addressed. The original program was developed using a collaborative process involving workshops attended by multiple stakeholders to identify research priorities. To date, the program has significantly improved our knowledge of Pilbara northern quolls, particularly in relation to effective survey and monitoring techniques, the influence of habitat quantity, configuration, and composition on occupancy, movement ecology, population dynamics and structure, and the threat posed by introduced predators. The efficacy of artificial refuges that were created to replicate natural denning habitat has also been investigated. Suggested future research directions focus on refining the northern quoll regional monitoring program, understanding how interacting threats such as introduced predators, fire, and herbivore grazing influence northern quoll populations in the Pilbara, and how best to mitigate other threats such as mining associated activities and the impending cane toad invasion.

Modelling polar bear maternity den habitat in east Svalbard

We evaluated a novel tool that predicts possible maternity den habitat of the polar bear (Ursus maritimus) based on a physical snow transport model, a digital terrain model and weather data. We observed and compared den locations in three important denning areas in east Svalbard (Kongsøya, n = 288; Svenskøya, n = 86; Hopen, n = 115) with modelled snowdrift distributions for 24 years. Accounting for a likely position uncertainty of 100 m, 69% of all dens were located within year-specific modelled snowdrifts. These covered on average 1.8%, 2.1% and 24.7% of the three study islands, respectively. Our snowdrift model accurately predicted maternity den positions (R2 = 0.42, area under the receiving operating characteristic curve [AUC] = 0.85). A model based on slope and altitude, also predicted den positions reasonably well (R2 = 0.35, AUC = 0.88). Habitat maps identifying both current and future areas for maternity denning will become important in managing the Barents Sea population as well as other Arctic populations where changes in sea-ice conditions alter the accessibility to traditional denning areas.

Multi-scale habitat selection model assessing potential gray wolf den habitat and dispersal corridors in Michigan, USA

Following decades of absence, the gray wolf (Canis lupus) has recolonized much of the northern Great Lakes region from Canada and remnant populations in northern Minnesota. The wolf population in Michigan’s Upper Peninsula may now be reaching saturation, with evidence that some dispersing individuals have traversed the Straits of Mackinac during ice-over winter conditions indicating potential recolonization of northern Lower Michigan. While previous research suggests suitable habitat exists in northern Lower Michigan to support a small wolf population, habitat availability at other hierarchical levels, including den habitat and the ability of individuals to disperse successfully among suitable habitat patches, has not been assessed. We evaluated the den habitat availability and landscape connectivity using a multi-scale modeling approach that integrates hierarchical habitat selection theory as well as spatial structure to assess whether corridors exist for wolves to successfully recolonize and raise pups in northern Lower Michigan. We used expert opinion, scientific literature, and geographical information systems to develop models of landscape suitability, resistance, and least-cost path analysis to identify dispersal corridors throughout the Upper and northern Lower Peninsulas of Michigan. Based on our models, the Upper Peninsula was almost entirely amenable to wolves for both denning and dispersing, particularly in the western portion of the peninsula. Our estimates indicate that over 1900 km2 of high quality den habitat exists in northern Lower Michigan, but landscape permeability between these habitat patches appeared relatively low relative to Upper Michigan. We delineated several corridors of high quality habitat in the Upper Peninsula that may facilitate dispersal in to Lower Michigan. Dispersal corridors were of moderate quality in northern Lower Michigan, representing higher mortality risk but potentially capable of promoting recolonization of high-quality habitat areas. Conservation efforts within these identified corridors may further increase the potential for successful recolonization and establishment of viable long-term breeding populations of gray wolves in northern Lower Michigan.

Den habitat selection of the chinese bamboo rat (Rhizomys sinensis) in Northern Guangxi China

A habitats comprises a range of environmental features that provide adequate resources for wildlife to survive. Consequently, the criteria of habitat selection by animals, combines a wider spectrum of both environmental and other factors, with major prerequisites being food resources, availability of shelter and suitable conditions for reproduction. The den habitat selection of the Chinese bamboo rat (Rhizomys sinensis) was studied in Yuanbaoshan Nature Reserve, Guangxi China. The Vanderloeg and Scavia selectivity index (Ei) indicates that the Chinese bamboo rat shows a preference for all habitat features except for slope, slope position and distance to water (P>0.05). Chi-square goodness of fit test showed that canopy density, shelter from wind, distance between shrubs, shrub density, elevation, southern aspect, human disturbance and food abundance, were the preferred features (P less than 0.05). With regards to human disturbance, the Chinese bamboo rat preferred places >1000 m away from human habitation. An eastern and southern sloping direction, a 20°^~40° slope and an elevation range of >1800m were more frequently used. The Chinese bamboo rat prefers habitats lying above 1000m in elevation with high shrub density (with shrub separation under 0.1m). Principle component analysis indicates that concealment factors, geographical factors, interference factors, food factors, and water factors affect the den habitat character of the Chinese bamboo rat. Our results support the notion that the habitat preferences of the Chinese bamboo rat are a tradeoff between suitable habitat features and avoidance of potential human interactions.

Modeling snowdrift habitat for polar bear dens

Throughout the Arctic most pregnant polar bears (Ursus maritimus) construct maternity dens in seasonal snowdrifts that form in wind-shadowed areas. We developed and verified a spatial snowdrift polar bear den habitat model (SnowDens-3D) that predicts snowdrift locations and depths along Alaska's Beaufort Sea coast. SnowDens-3D integrated snow physics, weather data, and a high-resolution digital elevation model (DEM) to produce predictions of the timing, distribution, and growth of snowdrifts suitable for polar bear dens. SnowDens-3D assimilated 18 winters (1995 through 2012) of observed daily meteorological data and a 2.5m grid-increment DEM covering 337.5km2 of the Beaufort Sea coast, and described the snowdrift depth distributions on 30 November of each winter to approximate the timing of polar bear den entrance. In this region of Alaska, winds that transport snow come from two dominant directions: approximately NE to E (40–110°T) and SW to W (210–280°T). These wind directions control the formation and location of snowdrifts. In this area, the terrestrial, coastal mainland and barrier island banks where polar bear dens are found average approximately 3m high. These banks create snowdrifts that are roughly 2m deep, which historical den analyses suggest is approximately the minimum snow depth required for a polar bear den. We compared observed den locations (n=55) with model-simulated snow-depth distributions for these 18 winters. For the 31 den locations where position accuracy estimates were available in the original field notes, 29 locations (97%) had a simulated snowdrift suitable for denning within that distance. In addition, the model replicated the observed inter-annual variability in snowdrift size and location at historical den sites, suggesting it simulates interactions between the terrain and annual weather factors that produce the snowdrifts polar bears use for dens. The area of viable den habitat ranged from 0.0ha to 7.6ha (0.00–0.02% of the 337.5km2 simulation domain), depending on the winter. SnowDens-3D is available to help management agencies and industry improve their prediction of current polar bear den sites in order to reduce disturbance of denning bears by winter recreational and industrial activities.

Application of a species distribution model to identify and manage bear den habitat in central British Columbia, Canada

Several mammals have adapted to harsh winter conditions by adopting hibernation strategies that enable them to survive periods of unfavourable environmental conditions. At northern latitudes, black and brown bears can be in a state of hibernation for up to seven months. As a result of this prolonged occupation of one small space, bears can be vulnerable to environmental and human caused disturbances. In this study, we developed a predictive model that identifies potential den habitat for black bears that can assist with management planning for industrial land development activities. We identified 40 dens (17 excavated in soil and 23 natural rock cavities) and used fine‐scale information to determine how dens were positioned in forest stands. We found that bears denned in areas on mid to upper slope positions and that soil dens were located mainly in clay‐loam soil complexes while rock cavity dens were either caves or cavities in boulder piles. Den location was distant from portions of the study area with relatively high road density. We then used resource selection functions to predict where bear dens might be located on the landscape. When applied to the GIS data, the averaged coefficients suggested that 3.1% of the study area had a high suitability ranking as den habitat while 9.1%, 14.6%, and 73.2% had mid, low, and limited suitability, respectively. In our study area, habitat for den sites is reasonably predictable and should be considered during the planning of industrial activities.

Den selection by grizzly bears on a managed landscape

Hibernation is an adaptive strategy to avoid harsh environmental conditions and seasonal limitations in food and water. Unlike most hibernators, grizzly bears (Ursus arctos) are aroused easily while in dens and disturbances while denning can result in fitness costs if bears become active during this period. Our objectives were to determine den selection of male and female grizzly bears at multiple spatial scales in the boreal forest and Rocky Mountains of Alberta, Canada. Grizzly bears in Alberta are designated as threatened. However, little is known about den selection by grizzly bears in the boreal forest and the current land and forest management plans do not include any mitigation measures to minimize possible impacts on the denning habitat of grizzly bears. We compared dens to random available locations within fall home ranges using geographic information system– derived anthropogenic, land cover, landscape, and food resource variables. Male and female grizzly bears had similar habitat requirements when selecting dens, and females did not avoid sites associated with a greater probability of encountering males. At the broadest scale investigated, grizzly bears avoided wetlands, and selected high-elevation, dry conifer stands with abundant high-quality spring food. At more localized scales, grizzly bears selected areas of low road densities and dense conifers associated with little high-quality autumn food. Slope angle had the most influence on den selection followed by percent autumn food, road densities, percent wetland, and percent spring food. We recommend limiting human disturbance, including open roads, within core grizzly bear conservation areas for areas with high suitable den habitat.

Late winter and early spring home range and habitat use of the endangered Carolina northern flying squirrel in western North Carolina

ESR Endangered Species Research Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsSpecials ESR 23:73-82 (2014) - DOI: https://doi.org/10.3354/esr00561 Late winter and early spring home range and habitat use of the endangered Carolina northern flying squirrel in western North Carolina W. Mark Ford1,*, Christine A. Kelly2, Jane L. Rodrigue3, Richard H. Odom4, Douglas Newcomb5, L. Michelle Gilley6, Corinne A. Diggins7 1US Geological Survey, Virginia Cooperative Fish and Wildlife Research Unit, Blacksburg, Virginia 24061, USA 2North Carolina Wildlife Resources Commission, Asheville, North Carolina 28803, USA 3US Forest Service Northern Research Station, Princeton, West Virginia 24740, USA 4Geospatial and Environmental Analysis, Virginia Tech, Blacksburg, Virginia 24061, USA 5US Fish and Wildlife Service, North Carolina Field Office, Raleigh, North Carolina 27606, USA 6Department of Biology and Marine Biology, University of North Carolina-Wilmington, Wilmington, North Carolina 28403, USA 7Department of Fisheries and Wildlife Conservation, Virginia Tech, Blacksburg, Virginia 24061, USA *Corresponding author: wmford@vt.edu ABSTRACT: The Carolina northern flying squirrel Glaucomys sabrinus coloratus is an endangered subspecies that is restricted to high elevation forests in the southern Appalachian Mountains. Owing to rugged terrain and nocturnal habits, the subspecies’ natural history, home range characteristics and habitat preferences are poorly known. We radio-tracked 3 female and 2 male Carolina northern flying squirrels during late winter through spring 2012 in the Pisgah National Forest, North Carolina, USA. Tracked squirrels used 13 yellow birch Betula alleghaniensis and 9 red spruce Picea rubens as diurnal dens. Ten of the yellow birch dens were in cavities, whereas the remainders were dreys. Conversely, 8 of the red spruce dens were dreys and one was in a cavity. Mean (±SE) female 95 and 50% adaptive kernel home ranges were 6.50 ± 2.19 and 0.93 ± 0.33 ha, respectively, whereas the corresponding values for males were 12.6 ± 0.9 and 1.45 ± 0.1 ha, respectively. Squirrels used red spruce stands with canopies >20 m more than expected based on availability at the landscape and home range scales. Results should be interpreted cautiously because of small sample sizes and seasonal observations; however, they provide evidence that although northern hardwoods such as yellow birch are an important den habitat component, mature red spruce-dominated habitats with complex structure provide foraging habitats and are also den habitat. Our findings support efforts to improve the structural condition of extant red spruce forests and/or increase red spruce acreage to potentially benefit Carolina northern flying squirrels. KEY WORDS: Carolina northern flying squirrel · Habitat use · Home range · Red spruce · Southern Appalachians Full text in pdf format PreviousNextCite this article as: Ford WM, Kelly CA, Rodrigue JL, Odom RH, Newcomb D, Gilley LM, Diggins CA (2014) Late winter and early spring home range and habitat use of the endangered Carolina northern flying squirrel in western North Carolina. Endang Species Res 23:73-82. https://doi.org/10.3354/esr00561 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in ESR Vol. 23, No. 1. Online publication date: January 28, 2014 Print ISSN: 1863-5407; Online ISSN: 1613-4796 Copyright © 2014 Inter-Research.

Using Bobcat Habitat Suitability to Prioritize Habitat Preservation on a Suburbanizing Barrier Island

ABSTRACT Many land‐trust organizations attempt to preserve habitat that will benefit specific wildlife species or suites of species. With limited resources available, these organizations need tools to prioritize preservation efforts. One such organization, the Kiawah Island Natural Habitat Conservancy (KINHC), is attempting to preserve wildlife habitat in the face of ever‐increasing property values and development pressure on Kiawah Island, South Carolina, USA. We modified an existing bobcat (Lynx rufus) habitat suitability index model, which focuses on suitability of habitats for food, by including components for concealment cover and den habitat. We developed a windows‐based computer program that calculates modified habitat suitability index (MHSI) values that can easily be imported into a Geographic Information System for display in map form, allowing for frequent reevaluation of site‐specific habitat suitability as land‐cover patterns change. We used locations collected from radiocollared bobcats to assess validity of the food and cover components of the MHSI. Bobcats used areas identified as highly suitable for food more than expected during nocturnal time periods (G52 = 640.9, P < 0.001) and areas identified as highly suitable for cover more than expected during diurnal time periods (G37 = 1,194.0, P < 0.001). Our approach for evaluating bobcat habitat suitability will allow KINHC to identify parcels that likely provide the greatest ecological benefit to bobcats and their associated wildlife community. Our approach could be altered to consider habitat requirements of other species, or multiple species, at virtually any location for which fine‐scale land‐cover data are available.

Brown Bear Den Habitat and Winter Recreation in South‐Central Alaska

ABSTRACT Increasing demand for backcountry recreation opportunities during winter (e.g., snowshoeing, helicopter‐assisted skiing, snowmobiling) in steep, high‐elevation terrain has elevated concern about disturbance to brown bears (Ursus arctos) denning on the Kenai Peninsula, Alaska, USA. To help identify areas where such conflicts might occur, we developed a spatially explicit model to predict potential den habitat. The model indicated brown bears selected locations for den sites with steep slopes, away from roads and trails. Den sites were associated with habitat high in elevation and away from potential human contact. We then compared areas with the highest probability of providing den habitat with patterns of snowmobile and nonmotorized recreation on a portion of the Kenai Peninsula. We found limited overlap between the 2 recreation activities and potential den habitat for brown bears. At the landscape scale, however, backcountry skiing overlapped more high‐quality den habitat than did snowmobile riding. Our results may be used by land management agencies to identify potential conflict sites and to minimize the potential effects of recreation activities on brown bears in dens.

DENNING ECOLOGY IN SYMPATRIC POPULATIONS OF SKUNKS (SPILOGALE GRACILIS AND MEPHITIS MEPHITIS) IN WEST-CENTRAL TEXAS

We examined den-site selection patterns for western spotted skunks (Spilogale gracilis) and striped skunks (Mephitis mephitis) co-occurring in mesquite brushland of Tom Green County, Texas. Sixteen S. gracilis and 14 M. mephitis were radiocollared to locate den sites from October 2001 through June 2003. Characteristics of dens were assessed using 23 habitat variables. S. gracilis favored den sites with dense mesquite (Prosopis glandulosa), shrubs, and cacti (Opuntia), whereas M. mephitis used these areas but also more open habitats. Den habitats of S. gracilis were more uniform than were those of M. mephitis, implying that S. gracilis is more specialized in den-site selection. Both species used multiple den sites, both above and below ground, rather than a primary den. Aboveground denning occurred year-round for both species. For S. gracilis, 56% (n = 60) of dens were above ground, but denning was more common above ground in the spring and summer. Aboveground denning was more common than belowground denning for M. mephitis in all seasons, representing 64% (n = 50) of all dens. Den habitat analysis suggests that S. gracilis, unlike M. mephitis, may be limited to areas with sufficient cover, including prickly pear cactus, for denning.

Predicting the Availability of Understory Structural Features Important for Canadian Lynx Denning Habitat on Managed Lands in Northeastern Washington Lynx Ranges

Abstract Stands identified as potential Canadian lynx denning habitat by a habitat suitability model were sampled in northeastern Washington for stand structure and understory structural features identified as important for denning lynx. Potential den structures were quantified by use of strip transects, and stand structure was quantified through an enhanced forest inventory approach focused on assessing understory and downed wood conditions. Information theoretic model selection methods indicated that the best model to predict potential denning understory structure availability included downed wood abundance, total basal area, and average stand diameter. The strong predictive ability of our models suggest that understory features important to denning lynx can be predicted using traditional inventory data with the addition of a downed wood line intercept methodology. In general, our study supports the suggestion that assessing downed wood availability will effectively address concerns over quantifying the availability of understory structural features identified as being important at lynx den sites. West. J. Appl. For. 20(4):224–227.

Remote Identification of Polar Bear Maternal Den Habitat in Northern Alaska

Polar bears ( Ursus maritimus ) give birth in dens of ice and snow to protect their altricial young. During the snow-free season, we visited 25 den sites located previously by radiotelemetry and characterized the den site physiognomy. Seven dens occurred in habitats with minimal relief. Eighteen dens (72%) were in coastal and river banks. These banks were identifiable on aerial photographs. We then searched high-resolution aerial photographs (n=3000) for habitats similar to those of the 18 dens. On aerial photos, we mapped 1782 km of bank habitats suitable for denning. Bank habitats comprised 0.18% of our study area between the Colville River and the Tamayariak River in northern Alaska. The final map, which correctly identified 88% of bank denning habitat in this region, will help minimize the potential for disruptions of maternal dens by winter petroleum exploration activities. Key words: aerial photography, Arctic National Wildlife Refuge, den habitat, maternal den, photo interpretation, National Petroleum Reserve – Alaska, polar bear, Prudhoe Bay, Ursus maritimus

Landform Selection and Soil Modifications Associated with Arctic Fox (Alopex lagopus) Den Sites in Yukon Territory, Canada

Arctic fox (Alopex lagopus) dens were examined in the unglaciated portion of the Yukon Coastal Plain and on Herschel Island. Den site selection relative to landform type was evaluated for 65 dens. On the Yukon Coastal Plain foxes established dens on sandy fluvial and wind-modified (dunes) fluvial deposits almost exclusively. On Herschel Island, moderately eroded landscapes were selected over noneroded, slightly eroded, and wetland terrain. The use of terrain maps proved to be useful in defining suitable den habitat. Chemical and physical properties of soil were compared on and immediately adjacent to 25 dens. Mean values for soil temperature, depth to permafrost, soil particle size, pH, N, and exchangable K were significantly different (P < 0.05) between on-den and off-den samples in both study areas. Total carbon, total phosphorous, and C:N were significantly different on Herschel Island but not on the Yukon Coastal Plain. The role of foxes in modifying soil chemical and physical properties is discussed relative to differences inherited through the parent material properties.

Mate choice and reproductive success of pikas

Factors affecting mate choice and female reproductive success were studied in a population of pikas, Ochotona princeps, in northeastern Oregon. Features of the den habitat (number of entrances to the den, size of the surrounding talus, distance to vegetation, amount of grass and forb present) and the mate or potential mate (weight and age) were analysed with respect to their effects on offspring production and survival, maternal survival and female mate choice. Female pikas chose mates primarily on the basis of the type of den available and the distance from the den to vegetation. These features were the primary determinants of the number of young weaned, but had no significant effects on maternal survival. Paternal weight was an important influence on offspring production, but its effect on female fitness was tempered by a negative effect on female survival. Characteristics important to female choice had no significant influence on the survival of young between weaning and natal dispersal and so cannot be considered to be male ‘handicaps’. Male pikas tended to be philopatric so that sons of males with territories that were attractive to females tended to inherit the attractive territories of their fathers. Female choice among pikas is thus best explained by Darwin's and Fisher's theories of intersexual selection.

Physical Characteristics of Arctic Fox (&lt;i&gt;Alopex lagopus&lt;/i&gt;) Dens in Northern Yukon Territory, Canada

Physical characteristics of arctic fox (Alopex lagopus) dens on Herschel Island and the Yukon Coastal Plain, Yukon Territory, Canada, are described. The preferred den habitat on Herschel Island is characterized by moderately eroded, sloping, gullied terrain, where foxes select sandy erosional mounds for denning. The preferred habitat on the Yukon Coastal Plain is fluvial landforms, where foxes select streamside cutbanks and occasional dunes for den location. Dens are generally associated with relatively warm, well-drained landscape positions. Burrow entrances are significantly oriented toward the south (P&lt;0.0025). Soils of dens are coarse textured, typically sandy loam to sand. Depth to permafrost is significantly greater under the den than at adjacent sites (p&lt;0.02). Certain unique soil profile characteristics, particularly the replacement of common cryoturbation (frost churning) features with those zooturbation (faunal mixing) and the formation of humus-rich surface horizons, appear to be the result of denning activities by foxes. Observed differences in soil temperature and depth to permafrost between den site soils and adjacent soils have likely been caused, at least in part, by denning activities.Key words: arctic fox (Alopex lagopus), dens, soil characteristics, habitat, distribution, northern Yukon Territory