Den Locations Research Articles

Den site selection by male brown bears at the population's expansion front.

Brown bears (Ursus arctos) spend about half of the year in winter dens. In order to preserve energy, bears may select denning locations that minimize temperature loss and human disturbance. In expanding animal populations, demographic structure and individual behavior at the expansion front can differ from core areas. We conducted a non-invasive study of male brown bear den sites at the male-biased, low-density western expansion front of the Scandinavian brown bear population, comparing den locations to the available habitat. Compared to the higher-density population core in which intraspecific avoidance may affect den site selection of subordinate bears, we expected resource competition in the periphery to be low, and all bears to be able to select optimal den sites. In addition, bears in the periphery had access to free-ranging domestic sheep during summer. We found that males in the periphery denned on high-elevation slopes, probably providing good drainage, longer periods of consistent, insulating snow cover and fewer melting-freezing events. Forests were the principal denning habitat and no dens were found in alpine areas. The Scandinavian brown bears have a history of intense harvest, including culling at the den. This may have exerted a selection pressure to avoid denning in open alpine habitat which compared to forests provide little cover. The bears denned away from main roads and in steep, rugged terrain, probably limiting human access. The odds for finding a bear den decreased with increasing distance to the population core where females could be found. Previous studies have documented directed movement of male brown bears from the male-biased population periphery toward the core areas during the mating season. In this way, denning males may be trading off between low resource competition and access to sheep in the low-density periphery, and mating opportunities in the higher-density population core.

Distribution Pattern of Red Fox (Vulpes vulpes) Dens and Spatial Relationships with Sea Turtle Nests, Recreation, and Environmental Characteristics

Although sea turtles are formidable prey as adults, their nests are highly vulnerable to terrestrial predation. Along the Southeastern coast of the United States, a primary predator of sea turtle nests is the red fox (Vulpes vulpes). Examining the relationship between fox populations and nest predation is often difficult due to coastal development. Masonboro Island, North Carolina is an undeveloped, natural, 13-km-long barrier island complex that is a component of the North Carolina National Estuarine Research Reserve (NERR). Masonboro Island consists of beaches, a dune ridge, back barrier flats, an expansive salt marsh, a lagoon, and spoil islands seaward of the Intracoastal Waterway. A field survey, which was conducted each spring from 2009 through 2012, recorded den entrance coordinates based upon recent use by foxes. Sea turtle nests were located using a similar survey methodology, which identifies viable and predated nests as well as false crawls. A series of spatial-temporal pattern analysis techniques were used to identify trends through time. The results indicated that: (1) fox den entrances and predated sea turtle nests were clustered throughout the island (p = 0.01); (2) den entrances in the northern part of the island were closer to the sea turtle nests than other locations on the island; (3) fox den entrances were positively correlated (p = 0.01) with dune height, (4) fox den entrances were located closer to the island boat access sites than expected (p = 0.01). A variety of spatial sensitivity tests were used to test the validity of the statistically significant cluster analyses. A Geographically Weighted Regression model was created to predict the location of fox dens using dune elevation, the distance to predated sea turtle nests, and the distance to boat access sites. The model accounted for 40% of the variance and had a small residual error, which indicates that the independent variables were statistically valid. Results from this project will be used by the NC NERR staff to develop management plans and to further study fox-related impacts on the island. For example, given the higher density of fox den entrances on the northern part of the island, managers may consider targeted wildlife control measures during the sea turtle nesting season to diminish predation.

Den selection by barren-ground grizzly bears, Mackenzie Delta, Northwest Territories

Animals living in highly seasonal environments such as the Arctic must cope with periods of reduced resource availability. During periods of food shortage, some resident mammals hibernate and rely on energy stores to overwinter. To conserve energy, hibernating grizzly bears (Ursus arctos) excavate dens that provide thermal insulation and safety. To determine the distribution and habitat characteristics used by grizzly bears for denning in the Mackenzie Delta, Northwest Territories, Canada, we used kernel density and resource selection function analyses based on 624 den locations collected in 1972–2014. We found that grizzly bear dens were broadly distributed with varying densities over the landscape. Our analyses showed that bears selected den sites with aquatic bed and low shrub land cover, with soil types composed of sand- , gravel- , and glacier-deposited rock, and southeastern- , southwestern- , and northern-facing slopes. Grizzly bears also selected for areas with sloped terrain. Open spruce forest was avoided. Information on grizzly bear denning habitat could be used to inform human land use planning and minimize human–bear conflicts.

Home range structure and space use of a female Amur leopard, Panthera pardus orientalis (Carnivora, Felidae)

Based on the locations reported over 15 months from the satellite GPS-collar of Amur leopard female, we estimated the size of its home range, the time of parturition, the location of dens, and hunting sites for large prey. The successive changes in the size and location of the home range and the core area during 30-day periods were traced. The home range remains stable, when the female moves without cubs outside the estrus period. During estrus and pregnancy, the size of the home range and the core area increases, and the core area is displaced. After the birth, the sizes of the home range and core area are sharply reduced. After the weaning of the Amur leopard female leaves the den and begins to move across the home range, the sizes of the range and the core area start to increase.

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.

Den site selection of wolves (Canis lupus) in response to declining caribou (Rangifer tarandus groenlandicus) density in the central Canadian Arctic

Wolves (Canis lupus) that den on the tundra of the central Arctic prey primarily on migratory barren-ground caribou (Rangifer tarandus groenlandicus). Prey densities in the vicinity of den sites are low, however, for a period each summer when caribou migrate to their calving and post-calving ranges. Eskers provide substrate where wolves can excavate den sites, but these landforms make up only a small proportion of the tundra landscape. We investigated the factors that influenced den site selection for wolves on the summer range of the Bathurst caribou herd, Northwest Territories, Canada. We used a long-term data set (1996–2012) of wolf den locations to develop a series of resource selection function (RSF) models representative of broad land-cover types, esker density, and annual variation in seasonal prey availability. We compared a temporal sequence of RSF models to investigate whether wolves altered selection patterns in response to a 90 % decline in caribou abundance (1996–2012). Eskers were selected denning habitat; the distribution of eskers may be limiting when wolf density is high. Covariates representing the seasonal distribution of caribou from early (5–18 July) and late (19 July–22 August) summer were the best predictors of den occurrence; these areas represented reliable availability of caribou over the greatest portion of the denning period. As the caribou herd declined, the seasonal summer ranges contracted northward towards the calving ground. Wolves did not exhibit a similar response. As such, the period of spatial separation between breeding wolves at den sites and the main distribution of caribou increased when herd abundance was low. The lack of a behavioural response is consistent with wolf–prey dynamics observed in other studies that suggest wolves strive to maintain consistent territories even following large decreases in resource availability. Such behaviours reduce fitness and have implications for pup survival and population growth.

Territoriality of giant otter groups in an area with seasonal flooding.

Territoriality carries costs and benefits, which are commonly affected by the spatial and temporal abundance and predictability of food, and by intruder pressure. Giant otters (Pteronura brasiliensis) live in groups that defend territories along river channels during the dry season using chemical signals, loud vocalizations and agonistic encounters. However, little is known about the territoriality of giant otters during the rainy season, when groups leave their dry season territories and follow fish dispersing into flooded areas. The objective of this study was to analyze long-term territoriality of giant otter groups in a seasonal environment. The linear extensions of the territories of 10 giant otter groups were determined based on locations of active dens, latrines and scent marks in each season. Some groups overlapped the limits of neighboring territories. The total territory extent of giant otters was correlated with group size in both seasons. The extent of exclusive territories of giant otter groups was negatively related to the number of adults present in adjacent groups. Territory fidelity ranged from 0 to 100% between seasons. Some groups maintained their territory for long periods, which demanded constant effort in marking and re-establishing their territories during the wet season. These results indicate that the defense capacity of groups had an important role in the maintenance of giant otter territories across seasons, which may also affect the reproductive success of alpha pairs.

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.

Structure of arctic fox (Alopex lagopus beringensis) colonies in the northern extremity of Bering Island

Data on the spatial structure of an Arctic fox (Alopex lagopus beringensis) colony were obtained in July-August 1995, using walk counts and observations near living dens around the Northern rookery of the northern fur seals located on Bering Island (Commander Islands). The home ranges of 31 Arctic fox families (61 adults and 145 pups inhabiting 66 dens) were found over 27 km of the coastline. Sixty individuals (3 adults and 57 pups) were marked by color ear-tags. Among adult foxes, 24 (39.3%) were recognized as females and 12 (19.7%) as males; the sex of 25 (41.0%) foxes was not recognized. Among 57 marked cubs, 26 (45.6%) were females and 31 (54.4%) were males. The best studied families (13) had 3–11 pups (6.7 ± 0.7, on average). The survival of cubs at an age younger than 2.0–2.5 months was 82.5%; 30.8% of the families consisted of more than two adults. The distribution of the Arctic fox dens and home ranges along the coastline has been studied; specific features of the location of dens have been described. In the studied area, Arctic foxes have been foraging on birds (67.6% of dens with food remains), northern fur seals (40.5), other marine mammals (13.5), Pacific salmon (29.7), and reindeer (2.7%), as well as on amphipods and voles. Rich constant food sources (rookeries, marine bird colonies, and spawning places of the blueback salmon) were found in 7 home ranges of the Arctic fox; 6 home ranges included temporary food sources (spawning streams of the humpback salmon); and 18 home ranges were poor in food resources. Arctic foxes whose home ranges lie within 6–7 km around a “food patch” used the concentrated food resources together. Food resources are supposed to become important only after the raised pups turn to self-feeding. Differences in the use of space, foraging and breeding of the two Arctic fox subspecies (A. l. beringensis and A. l. semenovi), and arrangement of colonies around the northern fur seal rookeries are discussed.

Elk migration patterns and human activity influence wolf habitat use in the Greater Yellowstone Ecosystem

Identifying the ecological dynamics underlying human-wildlife conflicts is important for the management and conservation of wildlife populations. In landscapes still occupied by large carnivores, many ungulate prey species migrate seasonally, yet little empirical research has explored the relationship between carnivore distribution and ungulate migration strategy. In this study, we evaluate the influence of elk (Cervus elaphus) distribution and other landscape features on wolf (Canis lupus) habitat use in an area of chronic wolf-livestock conflict in the Greater Yellowstone Ecosystem, USA. Using three years of fine-scale wolf (n = 14) and elk (n = 81) movement data, we compared the seasonal habitat use of wolves in an area dominated by migratory elk with that of wolves in an adjacent area dominated by resident elk. Most migratory elk vacate the associated winter wolf territories each summer via a 40-60 km migration, whereas resident elk remain accessible to wolves year-round. We used a generalized linear model to compare the relative probability of wolf use as a function of GIS-based habitat covariates in the migratory and resident elk areas. Although wolves in both areas used elk-rich habitat all year, elk density in summer had a weaker influence on the habitat use of wolves in the migratory elk area than the resident elk area. Wolves employed a number of alternative strategies to cope with the departure of migratory elk. Wolves in the two areas also differed in their disposition toward roads. In winter, wolves in the migratory elk area used habitat close to roads, while wolves in the resident elk area avoided roads. In summer, wolves in the migratory elk area were indifferent to roads, while wolves in resident elk areas strongly avoided roads, presumably due to the location of dens and summering elk combined with different traffic levels. Study results can help wildlife managers to anticipate the movements and establishment of wolf packs as they expand into areas with migratory or resident prey populations, varying levels of human activity, and front-country rangelands with potential for conflicts with livestock.

Distribution, characteristics and use of shelters by the Eurasian badger Meles meles along an altitudinal gradient in the Western Carpathians, S Poland

We studied the location of Eurasian badger (Meles meles) setts in relation to various environmental factors, and attempted to assess the role of competition with other burrowing carnivores and the importance of human activity on their sett selection in the Western Carpathians (southern Poland). Excavated dens (53 %), caves and rock crevices (43 %), and burrows under buildings (4 %), were used by badgers as permanent shelters. Setts were located mostly in foothills (< 680 m a.s.l.), but selection for den location within the lower montane zone (680-980 m a.s.l.) was also observed. Excavated setts were recorded only up to 640 m a.s.l., while setts in rock crevices occurred up to 1050 m a.s.l. Badger shelters were mainly situated in forests or covered by dense bushes. Badgers avoided northern slopes in all altitudinal zones, and located their burrows mostly on SE or W slopes in foothills, and S or E slopes in montane zones. Setts were placed further from human settlements and main roads, but closer to meadows with high earthworm biomass, when compared with random points. Within badger territories, 1-12 setts were recorded. Badgers occupying territories which included both foothills and montane zones used burrows at various altitudes, but their main setts used for overwintering, were located exclusively above 800 m a.s.l. We conclude that sett location by badgers in mountains is shaped not only by the availability of cover and geological factors influencing digging, but also by human pressure and distance to foraging areas.

Ecology of the red fox (Vulpes vulpes) in an agricultural landscape. 1. Den-site selection

Foxes concentrate their activities around den sites during the breeding period and regularly visit dens at other times of the year, meaning den location is an important consideration in efforts to control foxes and protect native prey species. We investigated factors that influence den-site selection by foxes to improve information on potential interactions with prey species, and assess the usefulness of targeting den sites for fox control. We measured 76 earthen and non-earthen fox dens on farmland in south-eastern Australia and compared these with paired random sites in relation to vegetation/land-use type, soil clay content, and proximity to landscape features (tree, water, fence and road). Most dens were earthen and primarily located in open farmland, whereas non-earthen dens were mostly found in roadsides. The proportion of non-earthen dens located by landholders (7.8% of 51 dens) was substantially lower than the proportion of non-earthen dens identified with radio-tracking (77.8% of 18 dens). The average clay content at earthen dens was significantly lower than that at non-earthen dens (t′ = –5.192, P &lt; 0.001) and random sites (t′ = –5.196, P &lt; 0.001). Soil texture was a key factor influencing fox den location, and this information should greatly improve fox control in agricultural landscapes for the benefit of native and non-native prey.

Despotism and risk of infanticide influence grizzly bear den-site selection.

Given documented social dominance and intraspecific predation in bear populations, the ideal despotic distribution model and sex hypothesis of sexual segregation predict adult female grizzly bears (Ursus arctos) will avoid areas occupied by adult males to reduce risk of infanticide. Under ideal despotic distribution, juveniles should similarly avoid adult males to reduce predation risk. Den-site selection and use is an important component of grizzly bear ecology and may be influenced by multiple factors, including risk from conspecifics. To test the role of predation risk and the sex hypothesis of sexual segregation, we compared adult female (n = 142), adult male (n = 36), and juvenile (n = 35) den locations in Denali National Park and Preserve, Alaska, USA. We measured elevation, aspect, slope, and dominant land cover for each den site, and used maximum entropy modeling to determine which variables best predicted den sites. We identified the global model as the best-fitting model for adult female (area under curve (AUC) = 0.926) and elevation as the best predictive variable for adult male (AUC = 0.880) den sites. The model containing land cover and elevation best-predicted juvenile (AUC = 0.841) den sites. Adult females spatially segregated from adult males, with dens characterized by higher elevations ( = 1,412 m, SE = 52) and steeper slopes ( = 21.9°, SE = 1.1) than adult male (elevation: = 1,209 m, SE = 76; slope: = 15.6°, SE = 1.9) den sites. Juveniles used a broad range of landscape attributes but did not avoid adult male denning areas. Observed spatial segregation by adult females supports the sex hypothesis of sexual segregation and we suggest is a mechanism to reduce risk of infanticide. Den site selection of adult males is likely related to distribution of food resources during spring.

Photographic Evidence of Florida Panthers Claw-Marking Logs

Abstract The secretive nature of Puma concolor (Puma) has made it difficult to observe them in the wild; therefore, researchers have primarily relied on radio telemetry to study Puma movements, habitat use, kill sites, and den locations. With the advent of digital infrared trail cameras, biologists are now recording previously unobserved Puma behavior, including urine-marking by females, wallowing, flehmening, and claw-marking logs. On 7 occasions, from August 2009—April 2010, we recorded 64 diagnostic sequential images of adult Puma concolor coryi (Florida Panther), of both genders, claw-marking the trunk of a downed Sable palmetto (Sabal Palm) log. Following a literature review and interviews with 11 professional Puma hunters, we concluded that this biological note represents the first photographic evidence of how male and female wild Pumas claw-mark logs.

Den use and selection by northern flying squirrels in fragmented landscapes

We studied den use and den-habitat selection by the Prince of Wales Island flying squirrel (Glaucomys sabrinus griseifrons) at multiple spatial scales in fragmented temperate rain-forest habitats because of the role dens play in the distribution, reproduction, and population density of this endemic subspecies. We observed differences in spatial patterns associated with den use between juveniles and adults: juvenile core denning areas were almost an order of magnitude larger than those of adults, and juveniles used about one-half the number of dens per month as adults. Female juveniles exhibited both the largest mean and maximum movements between consecutive dens among all age and sex classes. At the microhabitat scale of den selection snags were not selected over live trees, but flying squirrels primarily used cavities in snags and live trees. Flying squirrels also selected dens in the largest diameter live trees and snags, in snags with intermediate levels of decay, in live trees with more conks and visible bole entries, and in western hemlock (Tsuga heterophylla). At the broader scale of den selection flying squirrels chose den locations in neighborhoods with higher-volume forests and lower levels of fragmentation, although not lower absolute amounts of edge, than was available across the landscape. Our results suggest that extensive modification of landscapes from clear-cut logging and the creation of an early-seral matrix appeared to influence spatial patterns of den use in flying squirrels and den selection at the broader scale. When compared to patterns in a more-intact landscape, den selection at the microhabitat scale did not relate to differences in landscape context, suggesting additional factors might play an important role in den use across the region.

Ecological and anthropogenic influences on space use by spotted hyaenas

AbstractDue to increasing human encroachment into the remaining habitat of many large carnivore species, there is an immediate need to understand the ecological and anthropogenic factors influencing carnivore space use decisions. In particular, knowledge of changes in space use in response to disturbance, and the costs associated with these changes, will be critical in guiding conservation efforts. To investigate the ecological factors influencing carnivore space use, we intensively radiotracked members of two large social groups (clans) of spotted hyaenas Crocuta crocuta in the Masai Mara National Reserve, Kenya. In addition, we studied the influence of livestock grazing by comparing space use between two study clans that differed dramatically in exposure to grazing. Logistic regression modeling indicated that space use in the absence of livestock was most influenced by the location of the clan's communal den. However, hyaenas were also found to select shrubland, areas of high prey density, and proximity to seasonal streams. Movements of hyaenas exposed to livestock grazing were most influenced by vegetation type, with a strong avoidance of open grass plains. Den location and prey density had less influence on space use decisions in the disturbed than the undisturbed clan. Livestock distribution did not directly influence hyaena movements either during daytime, when livestock were present, or at night. We suggest that direct livestock avoidance was unnecessary due to the observed increased use of vegetative cover by hyaenas exposed to grazing livestock. The greater distances from the den, and from areas of high prey density at which hyaenas were found in disturbed than undisturbed areas indicates potential energetic costs incurred by disturbed hyaenas. Our results therefore suggest that reduced vegetative cover, as is often found outside protected areas, may result in more dramatic modifications of hyaena movements in the presence of livestock.

Octopus vulgaris in the Caribbean is a specializing generalist

The diet of Octopus vulgaris was determined from the remains of 649 prey items gath- ered from the middens of 38 dens in a small area off the Caribbean island of Bonaire. Remains of 35 species of gastropod (19% of the total), 19 bivalves (51%) and 21 crustaceans (30%) were identi- fied and examined for mode of entry into hard-shelled prey. Although 60% of the gastropods were drilled, neither the size/weight ratio nor the presence of an operculum determined whether drilling occurred. There were strong differences in prey preference among individual octopuses, and the Cardona niche breadth index (B') of the midden items was 0.08, indicative of specialization. Exam- ples include the exclusive preference for Pinna carnea by one den occupant. This study, by focusing on assessment of preference at specific den locations, is the first to show that while the population had a wide choice of prey items, the individual choices were much narrower, indicating that octo- puses were specializing generalists.

Den‐Site Characteristics of Black Bears in Rocky Mountain National Park, Colorado

Abstract: We compared historic (1985–1992) and contemporary (2003–2006) black bear (Ursus americanus) den locations in Rocky Mountain National Park (RMNP), Colorado, USA, for habitat and physiographic attributes of den sites and used maximum entropy modeling to determine which factors were most influential in predicting den‐site locations. We observed variability in the relationship between den locations and distance to trails and elevation over time. Locations of historic den sites were most associated with slope, elevation, and covertype, whereas contemporary sites were associated with slope, distance to roads, aspect, and canopy height. Although relationships to covariates differed between historic and contemporary periods, preferred den‐site characteristics consistently included steep slopes and factors associated with greater snow depth. Distribution of den locations shifted toward areas closer to human developments, indicating little negative influence of this factor on den‐site selection by black bears in RMNP.

Microclimate of daytime den sites in a tropical possum: implications for the conservation of tropical arboreal marsupials

AbstractTree cavities are an important shelter site for a variety of vertebrate species, including birds, reptiles and mammals. Studies indicate that in most taxa favoured tree hollows are those in larger trees and higher from the ground, generally thought to be related to decreased predation risk and a more optimal thermal environment. However, neither of these ideas has been tested definitively. Here, we investigate the microclimate of daytime den sites in tree hollows of common brushtail possums in tropical northern Australia. We compare tree and hollow characteristics of dens known to be used by possums, and those not known to be used, to determine whether possums choose trees with microhabitats with a more favourable daytime microclimate. Possums chose to den in tree hollows which were on average 1.6 °C cooler during the day, and were more buffered from temperature extremes, than other potential den locations. Important factors explaining daytime temperatures between hollows included height of the hollow, entrance width and tree diameter. Tropical arboreal marsupials have been identified as being particularly vulnerable to climate change and there are calls to identify and preserve natural refuges, such as tree hollows, which could buffer them from extreme temperatures. Our results highlight the value of older, larger hollow‐bearing trees as refuges from extreme temperature, the importance of which may become critical for some temperature‐sensitive species under the combined effects of continuing habitat loss and climate change.

Changes in the density and spatial distribution of red fox dens and cub numbers in central Poland following rabies vaccination

Increases in red foxVulpes vulpes (Linnaeus, 1758) numbers and densities have been found in all European countries involved in the rabies vaccination program. In Poland, the number of foxes has increased steadily since the 1990s. Between 1999–2000, the average density of foxes reached 1.3–2 ind./km2 in some parts of the country. The aim of the study was to estimate the change in fox population densities in central Poland during 1980–2006, and to assess the effect these changes have had on the spatial distribution of natal dens, mean numbers of cubs observed at occupied dens and the sedentary/nomadic fox ratio. Estimations of fox population density and numbers were based on three methods: (1) counts of tracks in snow, (2) locations of natal dens and counts of cubs, and (3) the battue (driving) method. The three methods of assessment were used continuously in our study area over a period of 25 years. Average yearly results were analysed and comparisons made between the periods before and after implementation of the anti-rabies vaccination. The results obtained with all three methods show a significant increase in the fox population, when the two analysed periods are compared. Increases in fox population densities correlated with increased numbers of breeding sites being located outside forests, from only single ones in the 1980s to 24% of the total in 2005. The average number of cubs per occupied den decreased significantly (by 11%) in comparison with before the anti-rabies vaccination period. The great increase (more than 100%) in fox numbers observed using the battue (driving) method suggest, that nomadic animals can form an important part of winter population in our study area.