Den Sites Research Articles

Urban coyotes select cryptic den sites near human development where conflict rates increase

AbstractThe establishment of coyote (Canis latrans) populations in urban areas across North America has been accompanied by increased rates of human–coyote conflict. One factor thought to promote physical conflict between coyotes and people or pets is the presence of coyote pups near natal dens; however, this idea has not been tested, and no multivariate study of den selection within cities has occurred. Our objectives were to conduct a multivariate analysis of third‐ (i.e., home range) and fourth‐order (i.e., den sites) habitat selection at dens and determine whether proximity to dens is associated with reports of physical conflict with coyotes. We found 120 dens by following coyote trails using snow tracking within urban green spaces that comprise presumed high‐quality habitat for coyotes in Edmonton, Alberta, Canada. We used resource selection functions to assess habitat selection for dens, testing variables related to land cover and anthropogenic features at the third order, and testing microsite habitat features via paired sites at the fourth order. We defined conflict encounters from comments in a community reporting database and used general linear models to assess their spatial proximity to the nearest den and prevalence during the pup‐rearing period compared to the rest of the year. Habitat selection was strongest at the fourth order, wherein coyotes selected for abundant hiding cover, steep slopes, and eastern exposure. The prevalence of physical conflict with coyotes increased during the pup‐rearing period. Conflict also increased near known dens as an overall effect and when reports occurred outside of naturalized urban areas. These results suggest that coyotes in Edmonton den in green spaces near human development in microsites that minimize detection by people via steep slopes and dense vegetation. We suggest urban wildlife managers increase public safety education about recognition of coyote denning habitat and coyote defensive behaviors, especially outside of naturalized urban areas, because of the observed increase in physical conflict near dens.

Den supplementation for black bears in coastal British Columbia

American black bears (Ursus americanus) require suitable den sites that provide security and cover to successfully survive the winter denning period. On Vancouver Island, British Columbia, Canada, black bears prefer to use cavities associated with large-diameter hollow trees or structures derived from trees (i.e., cavities in or under logs, root boles and stumps) as den sites. Extensive harvesting of coastal forests has reduced the availability of natural den structures such that their supply may affect population sustainability. I attempted to develop new methods to address the declining supply of denning opportunities by creating and testing new den structures constructed in trees, stumps and from plastic. Between 2014–2021, I created or deployed and monitored 17 potential den structures in 2 study areas that were believed to have low den supply. I documented up to 51 visits by bears at each structure; every one of the video-monitored structures was investigated at least 5 times. None of the plastic artificial den structures were used by bears, but an enhanced natural structure was used as a den over 4 consecutive winters. My work indicates that bears will find and investigate all natural or artificial denning structures in their environment, but artificial structures do not appear to be a viable method to mitigate losses of dens caused by forest harvesting.

Striped hyaena den site selection in Nilgiri Biosphere Reserve, India

AbstractThe den is a multi-purpose critical space of carnivores and provides a growth conducive refuge which ensures both substances and protection from interspecific predation and harsh climate. Selection of optimal den sites determined by various site-specific factors potentially reduces aversive interspecific interactions and provides cost-effective access to food sources. In this study, we have assessed the factors determining the den site selection by a small population of striped hyaena,Hyaena hyaenain a shared landscape dominated by large carnivores. We assessed den site selection as a function of vegetation patch characteristics, site-specific anthropogenic threats/activities and topographical variables using Bayesian algorithm through field collected binomial data on den use by the species. Our model suggested that hyaenas select rocky refugia surrounded by trees and tall grasses, situated on mountain slopes proximate to a water body. Our study consolidated the importance of undulating terrain in the species ecology and postulated the slope as an ‘energy-expensive’ terrain that refrains frequent movement of other carnivores, in turn providing more affordable denning space for the striped hyaena. This study provides critical information on denning ecology of last remaining major breeding population striped hyaena of southern India.

Terrain Features and Architecture of Wolverine (Gulo gulo) Resting Burrows and Reproductive Dens on Arctic Tundra

Burrowing species rely on subterranean and subnivean sites to fulfill important life-history and behavioral processes, including predator avoidance, thermoregulation, resting, and reproduction. For these species, burrow architecture can affect the quality and success of such processes, since characteristics like tunnel width and chamber depth influence access by predators, thermal insulation, and energy spent digging. Wolverines (Gulo gulo) living in Arctic tundra environments dig burrows in snow during winter for resting sites and reproductive dens, but there are few published descriptions of such burrows. We visited 114 resting burrows and describe associated architectural characteristics and non-snow structure. Additionally, we describe characteristics of 15 reproductive den sites that we visited during winter and summer. Although many resting burrows were solely excavated in snow, most incorporated terrain structures including cliffs, talus, river shelf ice, thermokarst caves, and stream cutbanks. Burrows typically consisted of a single tunnel leading to a single chamber, though some burrows had multiple entrances, branching tunnels, or both. Tunnels in resting burrows were shorter than those in reproductive dens, and resting chambers were typically located at the deepest part of the burrow. Reproductive dens were associated with snowdrift-forming terrain features such as streambeds, cutbanks on lake edges, thermokarst caves, and boulders. Understanding such characteristics of Arctic wolverine resting and reproductive structures is critical for assessing anthropogenic impacts as snowpack undergoes climate-driven shifts.

Modeling the spatial and temporal dynamics of land‐based polar bear denning in Alaska

AbstractAlthough polar bears (Ursus maritimus) of the Southern Beaufort Sea (SBS) subpopulation have commonly created maternal dens on sea ice in the past, maternal dens on land have become increasingly prevalent as sea ice declines. This trend creates conditions for increased human–bear interactions associated with local communities and industrial activity. Maternal denning is a vulnerable period in the polar bear life cycle, and den disturbance could lead to den abandonment, cub mortality, and negative population impacts. We used published long‐term data to parameterize a Bayesian hierarchical model of annual land den abundance during 2000–2015, in 4 regions of northern Alaska, USA, with current or potential future oil and gas activity. We also estimated long‐term (1982–2015) shifts in the spatial distribution of land dens within and among regions using kernel density estimation and assessed the influence of local and regional sea ice and snow conditions on den site selection using a random forest resource selection function. Our objectives were to quantify current den distribution and abundance, test for distributional shifts over time, and investigate if those shifts could be attributed to environmental variables related to den habitat. We estimated that between 2000 and 2015, the SBS contained a median 123 dens in a typical year, of which 68 occurred on land. The region between the Colville and Canning rivers, where most current oil and gas activity occurred, also contained the largest fraction of land dens. Overall, land dens were disproportionately concentrated on barrier islands and on land within 30 km of the coast. The probability of dens occurring on land varied from 1982–1999 to 2000–2015 in all regions, and the overall distribution of land dens shifted west between those periods. This regional‐scale change in den distribution was predictable based on spatial and temporal heterogeneity in snow and sea ice conditions within 50 km of individual den locations. Land denning is likely to become increasingly common with continued sea ice loss, and our results and modeling framework could be used to design additional mitigation strategies for reducing the risk of incidental take due to den disturbance.

Gimme shelter: anthropogenic structures as resting sites for American Marten (<i>Martes americana</i>)

Several species of martens (Martes spp.) are reported to use buildings as resting or den sites. However, such behaviour has not been attributed to American Marten (Martes americana). We report American Marten using occupied buildings and evidence of suspected use of an abandoned cabin, as resting sites in southern Yukon, Canada. These observations further highlight the behavioural flexibility of North American species of Martes with regard to using novel structures as resting sites.

A LATE MIOCENE MAMMAL ASSEMBLAGE REVEALS A COMPLEX TAPHONOMIC HISTORY IN FLUVIAL DEPOSITS OF CENTRAL ARGENTINA

ABSTRACT Micro- and macromammal remains from Cerro La Bota (late Miocene; La Pampa Province, Argentina) are taphonomically analysed. All remains form a single sample recovered from Chasicoan sediments (facies FA2) of the Cerro Azul Formation, constituted by a lateral and vertical erosive superposition of sandstone and conglomeratic bodies, formed by episodic development of perennial streams without flow division on a loessic substrate. The analysis reveals that micro- and macromammal remains originally accumulated independently and differently. Once each type of accumulation was buried in a loessic context, the development of streams gave place to a reworking process of fossils that were finally incorporated together into the stream channel. Taphonomic characteristics of micromammals are interpreted as the result of the leftover prey accumulated by predators, probably at a den site. Instead, the macromammals respond to an attritional accumulation of individuals inhabiting the area. Even considering the reworking as an important process that affected this assemblage, the taxonomic and taphonomic evidences suggest a relatively short time for its formation. The different taphonomic histories of the remains evidence a complex association that differs from other assemblages from the Cerro Azul Formation previously analysed, and it is here assigned to the channel-lag taphonomic mode.

Solitary vs communal use of nest boxes by the Edible Dormouse (Glis glis)

The Edible Dormouse often forms group associations in den sites. We characterize, over a 13-year period, how often the dormice rest alone or communally in nest boxes. The majority (87%) of individuals are solitary, resting alone during the daytime in nest boxes. In communal associations, groups of two or three individuals were the most common. We assessed the role of ambient temperature, seed mast, density of nest boxes and the surrounding vegetation on occupancy patterns. Seed mast and nest box density had a significant effect on group associations. Groups were more common in non-masting years. The lower the density of nest boxes at the study sites, the more common were group associations. In addition, a higher proportion of beech trees surrounding the nest boxes was associated with more frequent group associations.

Interspecific Killing of Vulpes vulpes (Red Fox) Kits at a Den Site by Canis lupus (Gray Wolf) in Isle Royale National Park, Michigan

Canis lupus (Gray Wolf or Wolf) have killed subordinate canids that scavenge on Wolf-killed prey, but little evidence is available for antagonistic behavior of Wolves toward other canids at interspecific den sites. We investigated clusters of locations from a global positioning system (GPS)collared male Wolf, translocated to Isle Royale National Park, MI, on 23 March 2019. On 17 May 2019, we investigated a GPS cluster of the Wolf and observed 3 Vulpes vulpes (Red Fox) kit carcasses at an excavated Red Fox den site. We report details from this event and evidence for interspecific aggression and implications for Wolf–Red Fox interactions. To our knowledge, this represents the first reported killing of Red Fox kits at their den by a Wolf. Limited reports of interspecific killings by Wolves of Red Foxes suggests this interaction was opportunistic and rare.

Population trends and Status of Smooth-Coated Otters (Lutrogale perspicillata) in Tungabhadra River ecosystem, Karnataka, India

In an increasingly disturbed and fragmented environment of the Tungabhadra River in Karnataka, we conducted a study to record the current status and population trends of Smooth-coated Otters. The goal was to identify regions with a lack of information on current status, gather information to create baseline data, and understand the otter species in this river. A total of 31 sampling stations was surveyed for two years from February-2018 to February-2020. The study area selected starts from Kudli, near Shivamogga in Karnataka to Kurnool of Andhra Pradesh, spread for 531/km. While surrounded by human-modified landscapes, the Tungabhadra River remains a significant habitat for flora and fauna, including otter species. Significant parts of the Tungabhadra river ecosystems lie beyond the security offered by protected areas; In these areas where existing conditions are poorly understood; New and accurate information on otter status and population trends are created using locally appropriate methodologies such as: documenting population trends, conflict incidents from local communities by questionnaire interviews and surveying for direct sightings and indirect credible evidence (spraints, footprints, den sites, food remains, and carcasses) to document the distribution of otters in the study area. The study reveals vital localities and hotspots of smooth-coated otters in the Tungabhadra River to promote conservation, restoration, and potential reestablishment in their ranges.

Classifying the effects of human disturbance on denning polar bears

Climate change is resulting in decreased sea ice extent and increased industrial activity in Arctic regions. In northern Alaska, USA, sea ice loss has increased the frequency of land-based polar bearUrsus maritimusmaternal dens, leading to greater potential for overlap between industrial activities and denning bears. Responses of denning bears to human disturbance could result in costly reproductive outcomes, although observation of these responses is logistically challenging and expensive. We developed a method to standardize the process of classifying the response of denning polar bears to disturbance using decision rules based on polar bear biology and denning chronology. We applied this method to 46 maternal polar bear dens exposed to human activity (e.g. vehicle traffic, ground-based monitoring). Because the timing of disturbance influences the response and subsequent fitness consequences, we determined outcomes specific to 4 denning periods: (1) den establishment (excavation to cub birth); (2) early denning (cub birth to 60 d old); (3) late denning (60 d old to emergence); and (4) post-emergence (emergence to den site departure). We classified the outcomes of 79 exposures as 37 having ‘no documented effect’ (no observed response), 7 as ‘behavioral’ (observed behavioral disruption), 17 as ‘early emergence’ (den emergence occurring earlier than an undisturbed emergence), 14 as ‘early departure’ (den site abandonment post-emergence earlier than if undisturbed), and 4 as ‘cub mortality’ (death or abandonment of ≥1 cub). Outcomes with potential fitness consequences occurred in every denning period. Our classification method facilitated a standardized approach that can be used to classify the outcome of den disturbance. Determining outcomes in relation to a specific denning period may facilitate improved implementation of mitigation strategies to reduce disturbance to denning bears.

Climate and behaviour influence thermal suitability of artificial hollows for a critically endangered mammal

AbstractArtificial hollows are commonly used to mitigate the scarcity of den and nest sites that threatens fauna species globally, but there is a risk that these do not provide suitable microclimates for the populations they are intended to support. We monitored temperature, humidity and occupancy in artificial dens (nest boxes and chainsaw‐carved cavities) provided for the critically endangered Leadbeater’s possum (Gymnobelideus leadbeateri) in south‐eastern Australian forests. Monitoring occurred over both winter and summer in five habitat types spanning a broad elevational gradient (110–1580 m asl). We then used a biophysical model to explore the physiological consequences of the den temperatures recorded, and the potential effectiveness of behavioural strategies in reducing thermoregulatory costs. Monitoring revealed that nest box temperatures tracked ambient over both seasons, ranging from −5.5°C to 48.5°C, while chainsaw hollows provided more stable internal conditions. However, we found that inferences regarding the thermal suitability of artificial dens were site‐specific, and dependent upon habitat type, season and assumptions around behavioural strategies. During winter, behaviours such as the construction of large, insulative nests and huddling are likely critical in overcoming high energy costs associated with poorly insulated artificial dens. In contrast, during summer high thermoregulatory costs were predicted for the warmest (lowland) site and coincided with low nest box occupancy. Our study reinforces the importance of factoring in local climates, and behavioural and physiological strategies employed by target taxa, when implementing artificial den programs to support fauna populations.

Decreased attractivity in female garter snakes treated with an aromatase inhibitor.

Most experimental studies on sexual signal regulation via hormone manipulation have focused on male signals, yet female signals demonstrate substantial phenotypic variation and hormone-dependent expression. Female red-sided garter snakes (Thamnophis sirtalis parietalis) produce a skin-based sex pheromone used by males in mate selection. The principle female sex steroid, 17 β-estradiol, controls pheromone production in snakes, but studies manipulating female garter snakes have produced conflicting results, relied on behavioral tests with males in the laboratory, and did not quantify pheromone expression. Because aromatase is the terminal enzyme in estradiol biosynthesis, we hypothesized that female garter snakes rely on aromatase to ultimately control pheromone production during the annual cycle of this species. To test this, we used a known pharmacological inhibitor of aromatase, fadrozole (FAD). Wild-caught female garter snakes were chronically treated via subcutaneous injections of either FAD (1.0 mg kg-1 ) or saline (control) for six months in the laboratory during the active period of the annual cycle then hibernated. In two separate field bioassays the next spring at the den site, FAD females received approximately 50% less courtship from wild, sexually active male garter snakes compared to SHAM females. Pheromone analysis revealed that four of the largest, unsaturated methyl ketones were specifically downregulated in FAD females, indicating that aromatase action is a crucial, permissive step in the maintenance of female attractivity.

Den-Site Selection by Eastern Spotted Skunks in the Central Appalachian Mountains of West Virginia

We assessed den-site selection of Spilogale putorius (Eastern Spotted Skunk) in the Appalachian Mountains of West Virginia by radio-tracking 8 individuals to 83 dens from January 2018 to October 2019. We measured local habitat characteristics at den sites and nearby, presumed unused paired sites and compared the habitat predictors via binary logistic regression. Results from the averaged model indicated greater understory cover from stems of Kalmia latifolia (Mountain Laurel) and Vaccinium spp. (Blueberry) and Gaylussacia spp. (Huckleberry), as well as medium to large rocks, and coarse woody debris increased the odds of a den site being used. Medium to large rocks were the most influential predictor of a den site. Our results suggest Eastern Spotted Skunks in this region would likely benefit from management practices that increase density of understory cover and coarse woody debris and preserve rocky outcroppings.

First Documentation of Two Types of Aboveground Den Structures in the Eastern Spotted Skunk (Spilogale putorius)

Spilogale putorius (Eastern Spotted Skunk) is a small, nocturnal carnivore that typically spends daylight hours resting in underground den sites. During a study on the den-site selection of S. p. ambarvalis (Florida Spotted Skunk) in the dry prairie of south-central Florida in 2016 and 2017, we tracked individuals to discernible aboveground structures composed of vegetation on 25 occasions. These structures were 1 of 2 easily distinguishable types: large mounds of vegetation primarily composed of shredded Serenoa repens (Saw Palmetto), or smaller cup-like structures with a horizontal entrance that resembled a ground-nesting bird's nest. These sites were occasionally reused by individual skunks, and on 1 occasion we observed 2 female spotted skunks occupying a site at the same time. Due to the absence of other wildlife species in the study area capable of making such structures, we believe that these structures were created by the skunks themselves. While Eastern Spotted Skunks are known to pull vegetation into their underground burrows, and have been documented occupying man-made structures (e.g., haystacks) as den sites, our observations represent the first documentation of aboveground, self-constructed structures being repeatedly used by this species. Use of these structures might be unique to Florida Spotted Skunk due to reduced predation risk or occasional flooding in the region that temporarily reduces availability of underground den sites.

Burrow Excavation by an Eastern Spotted Skunk and Visitation by a Long-Tailed Weasel

In this field note, we detail video evidence of Spilogale putorius (Eastern Spotted Skunk) further excavating a den site that was subsequently visited by Mustela frenata (Long-tailed Weasel). In October 2019 in Burke County, NC, we tracked a radio-collared Eastern Spotted Skunk to a small ground burrow. A camera trap was set outside the den entrance for 7 days. During this period, we observed that the burrow was occupied by 1 or more individual spotted skunks, and concurrently occupied by 2 spotted skunks on at least 1 occasion. The burrow was further excavated by 1 of the spotted skunks, representing the first recorded footage of this behavior in the Eastern Spotted Skunk. On 1 occasion, between visits to the den by the spotted skunks, a Long-tailed Weasel investigated the burrow. This observation represents one of the first close associations between these cryptic species.

Unicorn “holotype” skeleton from the Late Pleistocene spotted hyena den site Sewecken‐Berge (Germany)

AbstractLate Pleistocene Ice Age spotted hyena remains are described from the “Unicorn holotype skeleton” gypsum karst site Quedlinburg‐Sewecken‐Berge, Germany (Central Europe). The hyena population consists of adolescent to late adult individuals (96% of hyena NISP; 15% of megafauna NISP) indicating a commuting den site type. The comparisons to other European bone assemblages support hunting specialization on woolly rhinoceros (19% of NISP) and horses (27% of NISP). Specialization on bovids (Bison/Bos) can be added for this site. The megafauna contain few Eemian warm period remains of a large horse Equus ferus fossilis. Most (95%) of the megafauna is attributed to the Late Pleistocene glacial (Weichselian/Wuermian). Horse bones are dominated by distal leg elements from the smaller Przewalski horses Equus ferus przewalskii (26% of NISP). The Unicorn “holotype” skeleton originates from a composed horse skull, vertebrae and front legs, whereas the elephant remains added to this biologically not valid species must have been a straight‐tusked elephant tusk.

Habitat use by Long-tailed Weasels in a Fragmented Agricultural Landscape

Long-tailed weasels (Mustela frenata) have an extensive North American geographic range and tolerate a wide range of life zones, excluding some desert ecosystems. However, little is known of their habitat use in landscapes fragmented by agriculture, despite the fact that long-tailed weasel populations may be declining in these landscapes. During late winter-spring and late summer-autumn 1998–2000, we monitored 11 long-tailed weasels (seven males, four females) via radio telemetry to examine patterns of habitat use in an Indiana landscape fragmented by agriculture. Long-tailed weasels exhibited scale-dependent patterns of habitat selection (i.e., habitat selection within a landscape and selection of habitats within home ranges). Weasels selected forest patches, fencerows, and drainage ditches, whereas agricultural fields were avoided. Forest patches and fencerows provided suitable den sites and refuge cover from other predators and exhibited an abundant and diverse prey community. Drainage ditches provided movement corridors and access to free-standing, drinking water. The resource selection patterns and limited dispersal ability of long-tailed weasels compared to other carnivores are consistent with the notion that long-tailed weasels appear sensitive to agriculturally induced fragmentation of habitat.

The characteristics and consequences of African wild dog (Lycaon pictus) den site selection

The characteristics and consequences of African wild dog (Lycaon pictus) den site selection

Temporal activity shift in arctic foxes (Vulpes lagopus) in response to human disturbance

The rapidly growing interest for nature-based recreational activities threaten biodiversity values and increases the disturbance caused to wildlife. Several studies have demonstrated spatial and temporal activity shifts of animals in response to human disturbance. However, most studies investigate effects on how animals use an area of high tourism disturbance, such as a tourist resort or hiking trail, and not the effects of human disturbance at a key site for the animal, such as a denning or breeding site. In this study, we use photos from remote camera monitoring of arctic fox (Vulpes lagopus) dens with the aim to investigate the effects of various levels of tourism disturbance on the diurnal activity pattern and vigilance of breeding adult arctic foxes at the den site. We find a temporal shift towards a higher daytime activity at the den in response to high intensity tourism (71 ± 3.9% in disturbed areas compared with 53 ± 6.2% in undisturbed areas), which stands in contrast to an increased nocturnality seen in studies of many other species, including another study of arctic foxes. We suggest that the difference could be explained by the higher cost of avoiding a key site for the animal, as in this study, compared with avoiding a more general human disturbance in an area within the distribution range of the animal, as in most other studies. Increased time spent avoiding the perceived threat of humans could compromise other important activities and have potential negative effects on e.g. hunting or provisioning for the juveniles. Human disturbance focused at a key site, such as a denning or breeding site, can thereby be expected to have larger consequences than what is observed in most studies of disturbance effects on wildlife. Based on observations of both tourists and arctic foxes during close encounters in an area of high intensity tourism, we also find that they both respond behaviorally to each other. The potential for positive or negative feedback mechanisms in such relationships between tourists and wildlife highlights the importance of considering both sides of the complex interaction to find a balance between preserving biodiversity and ensuring continued possibilities for recreation.