Den Site Selection Research Articles

Den Site Selection of Lactating Female Raccoons Following Removal and Exclusion from Suburban Residences

Abstract In response to increases in human–wildlife conflicts in urban and suburban environments, many states have established nuisance wildlife control operator (NWCO) programs. Criticism has been leveled at such programs for insufficient emphasis on nonlethal means, particularly the exclusion and translocation of nuisance small and medium-sized mammals. We determined den site selection of lactating raccoons (Procyon lotor) after exclusion and subsequent release from a human residence. Fifteen of 20 females extracted from suburban residences returned to another house at least once. Of the den sites selected 2 months postrelease, 59% were in man-made structures. Our data suggest that most female raccoons removed and excluded from human dwellings will select another house if released on site. We contend this behavior is facilitated by suburban homeowners who fail to take the initiative to prevent entry of wildlife into their homes.

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.

Multiple Scale Den Site Selection by Swift Foxes, <em>Vulpes velox</em>, in Southeastern Colorado

Predation by Coyotes (Canis latrans) is a major source of mortality in Swift Fox (Vulpes velox) populations. Year-round den use by Swift Foxes is likely to be a predator avoidance strategy. Due to the importance of denning to Swift Fox ecology, we recorded den site selection of Swift Foxes in southeastern Colorado. Den site selection was recorded at two scales: microhabitat characteristics at the den and den placement within the home range. The number of den entrances, height and width of each entrance, aspect, hill position, slope, percent rock in soil, vegetative cover, and horizontal foliar density of 42 Swift Fox dens were examined during December 1999 – April 2000. This was compared to the same microhabitat characteristics at 42 random sites within Swift Fox home ranges to determine if Swift Foxes were using site characteristics according to their availability. Our results indicated that Swift Foxes were not highly selective of den sites based on the microhabitat characteristics evaluated in this study, although Swift Foxes selected areas of intermediate rock percentages. In addition, Swift Foxes were radio-tracked throughout the sample period and the location and frequency of use of known dens were recorded. Within the core area of home ranges, Swift Foxes used more dens (mean = 3.51 ± 1.70 (SD)), and had a higher frequency of use of dens (mean = 8.20 ± 6.01) than in the mid-range area (number of dens, mean = 0.90 ± 0.94; frequency, mean = 1.27 ± 2.12) and the boundary area (number of dens, mean = 0.34 ± 0.53; frequency, mean = 0.45 ± 0.93) of the home range. We discuss our results in terms of the importance of dens in facilitating escape from Coyotes. These results illustrate the need for examining den site selection at multiple scales to determine all selection factors, and to provide information useful for recovery and management efforts for this species.

Home-range size and selection of natal den and diurnal shelter sites by urban red foxes (Vulpes vulpes) in Melbourne

Selection of natal dens and diurnal shelters by red foxes (Vulpes vulpes) was investigated within the metropolitan area of Melbourne. Of 72 natal dens, 61% were in residential, public park, school or industrial lands. Most dens were beneath buildings (44.4%) or in earth banks (30.6%). The habitat categories in which dens were sited did not differ significantly from those described for London. Dens were more common beneath weatherboard buildings and were associated with properties that did not contain domestic dogs (Canis lupus familiaris). Diurnal shelter positions for 20 radio-collared foxes were obtained, and home-range data collected for 11 foxes. Estimated areas of adult home-range, for 100% minimum convex polygons (MCPs), varied between 11.5 and 45.8 ha, with from two to five diurnal shelter sites used in each home-range. Foxes showed a consistent preference for diurnal shelters associated with exotic weed infestations over ornamental and native vegetation or built habitats. Within these categories a diversity of substrates were used, including buildings, drains, graves, cypress trees, ornamental rockeries and garden beds. A preference for exotic weed infestations is an identifiable resource requirement for foxes in Melbourne and its removal may assist in reducing the abundance of urban foxes.

WINDSTORM DISTURBANCE EFFECTS ON FOREST STRUCTURE AND BLACK BEAR DENS IN SOUTHEAST ALASKA

We examined the relationships among forest susceptibility to windstorm damage, forest structure, and black bear winter den site selection in the coastal temperate rain forests of southeastern Alaska, USA. Forest susceptibility to maritime windstorms was determined by applying a wind‐disturbance model (WINDSTORM) to two study areas where bear dens had been identified by radio telemetry. We evaluated model predictions for forest structure against field data for one study area. As predicted, forests in wind‐protected landscapes contained features indicative of later stages of forest development where larger and older trees are more abundant. By contrast, forests located in storm‐susceptible locations contained higher tree densities, less variation in tree diameters, smaller trees, and less evidence of large, old trees with heart rot. Analysis of habitat use relative to its availability on the landscape indicates that bears selected wind‐protected landscapes over storm‐prone landscapes in both study areas for winter dens. The majority (58%) of den sites were located in forests most protected from catastrophic storm effects. By contrast, only 6% were located in forests most exposed to storm damage. Results suggest that forests most protected from catastrophic windstorm disturbance contain more suitable overwinter habitat for black bears as evidenced by den site selection.

Site selection and fidelity by crested porcupines for denning

The crested porcupine is a large rodent living in Central and North Africa, with a European distribution limited to Italy. Its biology and particularly its denning habits are inadequately known. Our study was carried out in a Mediterranean coastal area of central Italy. We radiotagged 13 adult porcupines, assessing their den site selection and use each month, from February 1998 to September 1999. Porcupines preferred steep, compact soils covered with dense vegetation, for denning. Each den was always used by the same 2 individuals, possibly forming a reproductive pair. Paired individuals seemed to show a greater site fidelitythan single ones. Intepretations of this behaviour are discussed.

Denning behavior and den site selection of grizzly bears along the Parsnip River, British Columbia, Canada

The Parsnip River area in British Columbia (BC), Canada, provides important habitat for grizzly bears (Ursus arctos). This area contains 2 adjacent topographic regions: (1) a relatively pristine portion of the Hart Ranges of the Canadian Rocky Mountains, and (2) a plateau on which timber harvests have occurred. Increasing human modification of both landscapes may affect the quality of grizzly bear habitat. Therefore, we examined denning behavior and den-site selection of grizzly bears in this area based on data from 61 grizzly bears radiocollared between 1997 and 2002 (34 plateau, 27 mountain bears). Adult females residing in the mountainous landscape arrived earlier to their denning areas (14 Oct versus 26 Oct), entered dens earlier (23 Oct versus 9 Nov), and emerged later (11 May versus 24 Apr) than plateau females, spending on average 36 days longer in their dens (200 days versus 164 days). Dens used in consecutive years by mountain females tended to be closer to one another (x = 2.4 km) than those of plateau females (x = 5.1 km). Dens in the mountains were excavations into sloping ground (74%), or natural caves (26%), using rocks as the primary stabilizing structure (47%). Resource selection functions (RSF) revealed that mountain grizzly bears selected dens in alpine habitats at mid-to-upper elevations. Plateau bears mainly excavated dens under the base of trees (90%), where roots stabilized material (80%). These dens primarily were located in older-aged forest stands ranging from 45–99 years (40%) or >100 years (50%); RSFs further revealed that grizzly bears on the plateau selected stands with tall trees. Plateau dens also were located away from roads, possibly because of less disturbance and because older trees were farther from roads.

A MULTI-RESOLUTION ASSESSMENT OF RACCOON DEN SELECTION

Abstract Many studies have been conducted on the ecology of raccoons (Procyon lotor), while few have examined raccoon den-site selection, particularly in agricultural and prairie landscapes. Furthermore, no studies have examined selection of den sites at multiple spatial scales. We examined den-site selection for 48 raccoons during 1997–1999 in an agricultural landscape in the Black Prairie physiographic region of east-central Mississippi, USA. Den types selected by raccoons differed by gender and season. Females used more cavity dens during young rearing, whereas males selected ground dens and brush piles. We found that den sites were located closer to crop fields, roads, and macrohabitat edges than random points. At the landscape level, den sites were associated positively with woody patch size, amounts of woody and grass edge, number of available patches of crop fields, and available area of lakes and ponds. Composition of habitats around den sites differed from composition of habitats within home rang...

Black Bear, <em>Ursus americanus</em>, Denning Chronology and Den Site Selection in the Northeastern Cascades of Washington

I studied Black Bear denning chronology and den site selection during 1995-1998 in the northeastern Cascade Mountains of Washington. Male Black Bears entered dens between 22 October and 19 November and emerged between 4 April and 7 May. Females entered dens somewhat sooner, between 15 October and 19 November, and emerged later than males, 4 April and 22 May. These den entry and emergence dates were similar to those reported at similar lattitudes in northwestern Montana. Roads had an important influence on den site selection by Black Bears in this study area. Bears selected dens in areas with no open roads >200 ha in size, >500 m from the nearest open road, and 1500-2000 m in elevation. The combination of information on denning chronology and site characterstics should allow managers to coordinate human activities to reduce the potential for disturbance to denning Black Bears.

Habitat use and diet of the red foxVulpes vulpes in an agricultural landscape in Poland

Red foxVulpes vulpes density, diet and den site selection were studied in a unwooded farmland of western Poland. During years 1999–2000 snow tracking was performed, and in 1999 dens were counted. Estimated population densities based on snow tracking were 2.1 and 1.79 individuals/km2 respectively, while den counts gave a value of 2.20 individuals/km2. Almost all dens were located on steep slopes, mainly on banks of drainage ditches (51%) and marsh banks (18%). Foxes markedly preferred southern exposure, while western slopes were avoided. The relatively high number of dens, their clumped distribution and the small number of breeding dens show that the studied population was organised in 5 clans. 26% of the dens were used only temporarily indicating that some of individuals use more than one den. Scat analyses revealed a high frequency of rodents, birds (mainly poultry) and garbage items in fox food (65.6, 47.9, 16.0% occurrence in scats, respectively). Fox adaptation to anthropogenic food sources and change in den site selection are discussed as main factors responsible for the occupation of farmland and in consequence, for the increase of fox densities in Poland.

SWIFT FOX DEMOGRAPHY, MOVEMENTS, DENNING, AND DIET IN NEW MEXICO

As a signatory of the Conservation Assessment and Conservation Strategy for Swift Fox, the state of New Mexico is required to manage swift foxes (Vulpes velox) with special diligence. However, basic ecological data for the swift fox in New Mexico are lacking. I examined swift fox demography, home range size, dispersal, den site selection, and diet in northeastern New Mexico. Juveniles comprised the most numerous age class. Body size measurements were generally as large or larger, and weights were smaller, than those reported from more northerly areas. Traumatic injury, presumably by coyotes (Canis latrans), was the primary cause of death. Annual survival rates for adults averaged 0.53. Of 36 swift foxes captured during the study, 4 remained alive on the study area, 21 died, and 11 left the study area by the end of 32 months of field work. The annual 95% MCP home range size estimate was 1,494.5 ha. Diet was dominated by invertebrates and mammals. For den sites, swift foxes preferred the vicinity of roads, areas with greater road density, low slope, hilltops, and sandy loam and clay soils.

Characteristics of current and historical kit fox (Vulpes macrotis) dens in the Great Basin Desert

We examined the ecological and physical characteristics of den sites for 13 adult kit fox (Vulpes macrotis) in western Utah from December 1998 to February 2001. We also compared current and historical den distribution among habitat types. The number of den sites used was not influenced by home-range size (P = 0.11) or season (P = 0.40), but was influenced by geographical area. Home-range size was smallest (P = 0.007) and the number of dens used was greatest (P = 0.009) in mountainous areas. Ecological and physical characteristics of single-use dens (n = 30) were compared with those of multiple-use (n = 53) and natal dens (n = 8). Characteristics that differed between den types included number of entrances (P = 0.0001), diameter of entrances (P = 0.003), and height of vegetation along transects (P = 0.0001). Natal den entrance azimuths were weighted towards a northwesterly aspect (P = 0.0022); however, single- and multiple-use den exits appeared to be randomly distributed. Historical changes in kit fox den site selection have occurred since 1959 (P < 0.0001). We characterized more dens in invasive grasslands and fewer in greasewood (Sarcobatus vermiculatus) habitats than previously described. The conversion of native habitat to grassland and the increase in coyote population may have altered kit fox distribution to include mountainous areas not previously described.

Den trees used by northern flying squirrels (Glaucomys sabrinus) in southeastern Alaska

Northern flying squirrel (Glaucomys sabrinus) dens are reportedly associated with features characteristic of older forests, and den availability is a potential limiting factor in younger forests. We assessed den sites used by northern flying squirrels in southeastern Alaska, where we expected den-site selection to differ from more southerly forests, owing to increased thermal stress but reduced predation and competition. We located 27 squirrels in 76 dens and compared den trees with 1875 matched random trees. Most dens ([Formula: see text]73%) were in cavities and 21% were at heights of [Formula: see text]3 m. This high rate of cavity use, including cavities low in the bole, likely reflects the importance of weatherproof dens in this cool wet region. Northern flying squirrels preferentially used trees with indicators of cavity presence, selecting for snags and for larger diameter trees with bole entries, conks, abundant mistletoe, and dead tops. Although cavity availability is probably not limiting populations in this region currently, cavity-supporting trees would be one of the last elements of old-growth forests to develop in intensively logged stands. Retention of small groups of large snags and live trees exhibiting evidence of disease or physical defects would ensure availability of denning structures after logging.

Forest composition around wolf (Canis lupus) dens in eastern Algonquin Provincial Park, Ontario

Den-site selection is a poorly understood aspect of wolf (Canis lupus) ecology, particularly for populations in forested ecosystems. Using a geographic information system and remote-sensing imagery, we examined patterns of habitat use around wolf dens in Algonquin Provincial Park, Ontario. Sixteen den sites were sampled for eight habitat types in their immediately vicinity, as well as at radii of 500, 1000, 1500, and 2000 m. We used a resource-selection ratio to determine whether specific habitat types were preferred or avoided at different radii relative to the total proportion of habitat types found within the study area. Wolves established dens in areas with significantly high proportions of pine forest up to and including a 1000-m radius and low proportions of tolerant and intolerant hardwoods within 500 m. We conclude that wolves establish den sites based primarily on the presence of pine forest, a habitat that is frequently logged within Park boundaries and subject to problems with regeneration after cutting. Dens sites are likely not limiting in this population, but our results suggest the need to protect current den sites at a relatively large spatial scale. These results also provide unique information to assess the potential for recolonization and reintroduction of wolf populations in other areas.

Resource Selection by Porcupines: Winter Den Site Location and Forage Tree Choices

Abstract We examined the importance of tree species composition and tree size-class distribution in determining the selection of winter den sites and forage trees by porcupines (Erethizon dorsatum). Porcupines selected winter den sites with a higher composition of sitka spruce, in all diameter size classes. However, statistically significant selection was found only for the 15.0–19.9 cm dbh size classes of sitka spruce. Porcupines displayed a statistically significant avoidance of 5.0–9.9 cm dbh and 10.0–14.9 cm dbh western hemlock trees when selecting winter den sites. When foraging around the den sites, porcupines showed a statistical avoidance of amabilis fir in all size classes and selected western hemlock, except the smallest size class (5.0–9.9 cm dbh). The results of this study indicate that porcupines do not choose winter den site locations based on the availability of preferred forage resources. Porcupines appear to choose den sites based on within-stand, patch variation in the proportion of sitka spruce and small dbh western hemlock. Forage trees are then selected, nonrandomly from specific resource categories around the den site. Porcupines in this study were found to feed on a mean of 0.54 new forage trees/day. Regression analysis revealed a positive linear relationship between new forage trees used/day and porcupine midwinter weight (y = 0.15x–0.54; r2 = 0.73). The results indicate that larger porcupines may produce a larger proportion of observed conifer tree feeding damage in second growth stands, as compared to smaller porcupines. West. J. Appl. For. 16(2):53–57.

Characteristics of Wolverine Reproductive Den Sites

Successful wolverine (Gulo gulo) reproduction may be linked to the availability and quality of reproductive dens sites, but little is known about wolverine reproductive dens, especially in North America. We present descriptions of wolverine dens in Idaho and Alaska, compare them to dens in other regions, and propose factors that may influence den-site selection. Our study includes 8 den sites used by 3 females over 4 years in northwestern Alaska and 7 sites used by 2 females over 4 years in central Idaho. We categorized reproductive dens of wolverines as either natal (used during parturition) or maternal (used subsequent to the natal den and before weaning). Dens in Alaska were usually long, complex snow tunnels with no associated trees or boulders. In contrast, dens in Idaho were always associated with fallen trees or boulders. All dens were covered with at least 1 m of snow. With few exceptions, wolverine dens described to date have been located in alpine, subalpine, taiga, or tundra habitat. Reports of dens in low elevation, densely forested habitats are rare. Factors which may have influenced selection of den sites included thermoregulatory advantages, protection from predators, suitability of the site during the spring thaw, and location of rearing habitat. We recommend managers consider limiting wolverine harvests and reducing human disturbance in wolverine denning g habitat.

Characteristics of American Marten Den Sites in Wyoming

We examined characteristics of den structures and den sites used by female American marten (Martes americana) for natal and maternal dens in the Sierra Madre Range, Wyoming. During 1988-95, we located 18 natal dens (parturition sites) and 97 maternal dens (sites where kits were present exclusive of parturition) used by 10 female marten. Important den structures included rock crevices (28%), snags (25%), red squirrel (Tamiasciurus hudsonicus) middens (19%), and logs (16%). Resource selection function (RSF) analysis showed that an individual selection model provided a significantly better fit than a null model or pooled selection model, indicating that the sample of marten selected maternal den sites that differed from random sites, and that individual animals did not select maternal den sites in the same manner. Six marten individually exhibited significant selection for maternal den sites within home ranges. Overall selection coefficients for maternal dens indicated the number of squirrel middens was the most important variable, followed by number of snags 20-40 em diameter at breast height (dbh), number of snags 2:41 em dbh, and number of hard logs 2:41 em in diameter. Selection of natal den sites was also significant via comparison between selection and no-selection models, with number of middens, number of Engelmann spruce (Picea engelmannii) and subalpine fir (Abies lasiocarpa) >20 em dbh, and number of hard logs 2:41 em in diameter the most important variables in descending order of importance. Large logs, large snags, and large, live spruce and fir trees are important characteristics for marten den sites in the central Rocky Mountains. The prominence of middens at den sites suggests red squirrels provide important denning structures as well as prey for marten.

Den site selection and utilization by the red fox in Hokkaido, Japan

Den site selection and den use by the red fox, Vulpes vulpes, were studied on the Nemuro Peninsula, eastern Hokkaido, Japan. Certain physical variables of 144 fox den sites were compared with those of 236 randomly selected control locations. The red foxes on the Nemuro Peninsula clearly preferred to den on slopes in woodlands near open spaces and streams. The seasonal pattern of den utilization was studied from June 1986 to May 1987. Red foxes used dens mainly during the period from January to June. Since this period coincides with the gestation, parturition and cub rearing periods of the red fox, it was confirmed that the red fox's den was fundamentally a breeding site. Almost all dens were observed each spring from 1986 to 1996 to establish whether they were used for breeding or not, and it was found that the number of fox families was stable during this decade.

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.

Aspects of the Use of Den Trees by Arboreal and Scansorial Marsupials Inhabiting Montane Ash Forests in Victoria

The time and height of emergence from den trees occupied by various species of arboreal marsupials inhabiting the montane ash forests of the Central Highlands of Victoria, in south-east Australia, were recorded from September 1988 to January 1989. There were significant differences in emergence time among most species of arboreal marsupials. Emergence time was strongly correlated with published values of body weight, field metabolic rate and standard metabolic rate. The entrance to the nest was higher in gliding species than those which are non-volant. Small species exhibited a significant preference for den sites with a hole as the entrance. The entrance of a den occupied by large species was typically a hole in a hollow branch or spout. The selection of den sites was related to the body size of the occupant. Differences in the type and height of the entrance to the nest, together with the time of emergence from the den, indicate partitioning of the nest tree resource between the various species inhabiting montane ash forests.