Den Use Research Articles

High energetic cost of color change in octopuses

For many animals, color change is a critical adaptive mechanism believed to carry a substantial energetic cost. Yet, no study to date has directly measured the energy expenditure associated with this process. We examined the metabolic cost of color change in octopuses by measuring oxygen consumption in samples of excised octopus skin during periods of chromatophore expansion and contraction and then modeled metabolic demand over the whole octopus as a function of octopus mass. The metabolic demand of the fully activated chromatophore system is nearly as great as an octopus’s resting metabolic rate. This high metabolic cost carries ecological and evolutionary implications, including selective pressures in octopuses that may influence the adoption of nocturnal lifestyles, the use of dens, the reduction of the chromatophore system in deep-sea species, and metabolic trade-offs associated with foraging.

Selection of den sites and chronology of denning by black bears in the eastern Sierra Nevada and western Great Basin.

Use of dens during winter is an important strategy for American black bears (Ursus americanus) for both energy conservation and reproduction; and occupancy of suitable den sites has implications for reproductive fitness. Denning strategies may change as a result of changing climatic conditions and habitat loss. Black bears occupy arid environments in the eastern Sierra Nevada and the western ranges of the Great Basin Ecosystem. Our objectives were to identify: (1) which physical characteristics of habitat influenced selection of den sites at multiple spatial scales and (2) which environmental factors influenced timing of entrance and exit of dens by females and males. We evaluated selection of den sites by black bears at three spatial scales (300, 1000, and 4000 m) from 2011 to 2022. Terrain ruggedness was important for selection of den sites at all spatial scales. Within a 300-m buffer from the den, bears selected den sites with rugged terrain, lower horizontal visibility, and greater canopy cover, resulting in more concealment and protection than that of the surrounding environment. Within 1000- and 4000-m buffers around each den, bears selected den sites with rugged terrain, northern aspects, and steep slopes. At the 4000-m scale, we observed interactions between sex with slope and distance to roads; females selected den sites on steeper slopes and closer to roads than did males. Females remained in the dens longer than males by entering earlier in the autumn and exiting later in the spring. Male bears exited their dens earlier with increasing consecutive days above freezing temperatures, but that relationship was weak for females. Knowing what characteristics are important for selection of den sites, and influence timing of denning, will be important for understanding how shifting climatic patterns will affect bears, particularly in arid environments that may be prone to wider fluctuations in climatic drivers of denning in the future.

Influencia del uso de refugios por las presas en el modelo de depredación de Volterra

In various previous works, different predation models have been analyzed considering the use of refuge by the prey population, without carrying out an exhaustive analysis of its dynamics. In some of them it is stated that the use of shelters or dens by a fraction of the prey population has a stabilizing effect on predator-prey interaction. One of the objectives of this work is to show that some of these new systems considering refuge may have the same topological portrait in the phase plane as the original; but in others the dynamics change strongly. In our research we will introduce modifications to the well-known Volterra model, considering various ways to express the number of prey in refuge. In several of them, local dynamics equivalent to the original model are obtained, confirming that results reported as new were previously known based on the original system, without taking into account the refuge of the prey. We conclude that the behavior of the systems depends on the mathematical expression to describe the number of sheltered prey.

Carnivore coexistence without competition: giant otters are more nocturnal around dens than sympatric neotropical otters.

Nocturnal activity of tropical otters is rarely reported. To date no studies have documented den use by sympatric giant (Pteronura brasiliensis) and neotropical otters (Lontra longicaudis). We used camera-traps to monitor den use by sympatric otters along an equatorial Amazonian river. Camera-traps provided evidence that giant otters were more nocturnal around dens than sympatric neotropical otters. Nocturnal activity was recorded in 11% of giant otter photos (n = 14 of 125 photos), but was recorded only once for neotropical otters. Den use by giant and neotropical otters overlapped spatially and temporally but not concurrently. We hypothesize that previously reported nocturnal activity in neotropical otters is facilitated by the absence or low density of giant otters. Our results also underscore the need to use complementary techniques together with den counts for monitoring otters as sympatric species can use the same dens.

Fission-fusion dynamics in the social networks of a North American pitviper.

Many animal species exist in fission-fusion societies, where the size and composition of conspecific groups change spatially and temporally. To help investigate such phenomena, social network analysis (SNA) has emerged as a powerful conceptual and analytical framework for assessing patterns of interconnectedness and quantifying group-level interactions. We leveraged behavioral observations via radiotelemetry and genotypic data from a long-term (>10 years) study on the pitviper Crotalus atrox (western diamondback rattlesnake) and used SNA to quantify the first robust demonstration of social network structures for any free-living snake. Group-level interactions among adults in this population resulted in structurally modular networks (i.e., distinct clusters of interacting individuals) for fidelis use of communal winter dens (denning network), mating behaviors (pairing network), and offspring production (parentage network). Although the structure of each network was similar, the size and composition of groups varied among them. Specifically, adults associated with moderately sized social groups at winter dens but often engaged in reproductive behaviors-both at and away from dens-with different and fewer partners. Additionally, modules formed by individuals in the pairing network were frequently different from those in the parentage network, likely due to multiple mating, long-term sperm storage by females, and resultant multiple paternity. Further evidence for fission-fusion dynamics exhibited by this population-interactions were rare when snakes were dispersing to and traversing their spring-summer home ranges (to which individuals show high fidelity), despite ample opportunities to associate with numerous conspecifics that had highly overlapping ranges. Taken together, we show that long-term datasets incorporating SNA with spatial and genetic information provide robust and unique insights to understanding the social structure of cryptic taxa that are understudied.

Use of dens by the desert fox in the desertic environment

The study was carried out on the use of dens by the desert fox in the desertic environment at Jajiwal Dhora and Guda Bhakri study sites in Jodhpur district of Rajasthan. Dens played a vital role in protecting desert fox and their pups from adverse environmental conditions. During study period total 104 dens were recorded out of them, 42 were resting dens and 62 were breeding dens. At Jajiwal Dhora study site 72 dens were observed and at Guda Bhakari study site 32 dens were noted. The desert fox used the dens for pup rearing, resting and saving themselves from different climatic factors such as heavy rain, dust storms, warm air and coldness. Desert fox use the den according to the seasonal changes. Northern-facing dens were mainly used during summer, while southern-facing dens were used in winter. The rodents, birds and bushes dominated areas and agricultural fields were mainly preferred by the desert fox for digging the dens. Direct observation, questionnaire and interview methods were used for the investigation.

MOVEMENTS BY SAN JOAQUIN KIT FOXES (VULPES MACROTIS MUTICA) BETWEEN URBAN AND NONURBAN HABITATS: IMPLICATIONS FOR INTERPOPULATION DISEASE TRANSFER.

Sarcoptic mange epidemics erupted in two of the remaining populations of endangered San Joaquin kit foxes (Vulpes macrotis mutica). Both populations are in urban habitats in the cities of Bakersfield and Taft, California, USA. The risk of disease spread from the two urban populations to nearby nonurban populations, and then throughout the species range, is of considerable conservation concern. To date, mange has not been detected in any nonurban populations despite considerable surveillance effort. The reasons for the lack of detections of mange among nonurban foxes are unknown. We monitored urban kit fox movements using geographic positioning system (GPS) collars to test the hypothesis that urban foxes were not venturing into nonurban habitats. Of 24 foxes monitored December 2018 to November 2019, 19 (79%) made excursions from urban into nonurban habitats from 1-124 times. The mean number of excursions per 30 d was 5.5 (range 0.1-13.9 d). The mean proportion of locations in nonurban habitats was 29.0% (range 0.6-99.7%). The mean maximum distance that foxes traveled into nonurban areas from the urban-nonurban interface was 1.1 km (range 0.1-2.9 km). Mean number of excursions, proportion of nonurban locations, and maximum distance into nonurban habitats were similar between Bakersfield and Taft, females and males, and adults and juveniles. At least eight foxes apparently used dens in nonurban habitats; shared use of dens may be an important mode of mange mite transmission between conspecifics. Two of the collared foxes died of mange during the study and two others had mange when captured at the end of the study. Three of these four foxes had made excursions into nonurban habitats. These results confirm a significant potential for mange to spread from urban to nonurban kit fox populations. We recommend continued surveillance in nonurban populations and continued treatment efforts in the affected urban populations.

Sloth Bear (Melursus ursinus) Maternity Denning Behavior Observations at Indira Gandhi Zoological Park, Visakhapatnam, India

The Sloth bear is an average-sized black bear with a long, shaggy coat. a long ruff of hair around the back, and a white V- or Y-shaped mark on the breast. Males that are considered to be "large" often top out around 145 kg and 170 centimeters. An endangered species, the sloth bear (Melursus ursinus) is extensively spread over the Indian subcontinent, including India, Nepal, Bhutan, Sri Lanka, and perhaps Bangladesh. It is found in wooded regions from the Indian peninsula to the foothills of the Himalayas. Despite the species' widespread occurrence, nothing is known about its ecology or behavior. We studied den characteristics and maternity denning behavior in captivity. The den use was more from June to August, possibly to take shelter against heavy rains from the southwest monsoon. (June - September). Breeding observed based on the association of adult females and males as well as the birth of cubs revealed that mating is likely to occur during late summer or early monsoon and cubs are born mostly during November-December. This study presents observations on den site characteristics and maternal denning behavior patterns of sloth bears in captivity at Indira Gandhi Zoological Park, Visakhapatnam.

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.

Zoo Closure Does Not Affect Behavior and Activity Patterns of Palawan Binturong (Arctictis binturong whitei)

Exploring the interaction between humans and animals has become increasingly important in the evaluation of well-being for species housed in zoos and aquaria. The COVID-19 pandemic saw the global closure of zoos and aquaria to visitors. Chester Zoo, U.K., was no exception, with the charity shutting its doors for the longest period in its 90-year history. Whilst access to site was strictly limited to essential animal care staff, recent investment in networked infrared CCTV camera systems allowed some species to be monitored remotely during this extraordinary period of zoo closure. Here, we used this equipment to investigate whether zoo closure influenced activity patterns and behavior of two adult Palawan binturong, Arctictis binturong whitei. The cameras facilitated behavioral monitoring over 24 h enabling the collection of a full activity budget, which revealed a natural crepuscular activity pattern. Overall, visitor presence was found to have a neutral effect on this species, with no significant difference observed in time spent engaging in den use, vigilance or travel behaviors during zoo open and zoo closed conditions. A neutral visitor effect was found when evaluating behavior over a 24 h period and during hours which the zoo would normally be open to visitors (10:00–16:30). This research presents new information on this elusive and understudied species in captivity, and promotes investment in monitoring equipment which enables more comprehensive behavioral sampling than traditional visitor-effect methods.

Redundancy analysis reveals complex den use patterns by eastern spotted skunks, a conditional specialist

AbstractWildlife managers tasked with understanding habitat and resource selection at the population level attempt to characterize patterns in nature that aid and inform conservation. Resource selection functions (RSFs), such as discrete choice analyses, are the standard convention to characterize the effects of habitat attributes on resource selection patterns. These tools are invaluable for wildlife management and conservation and have proven successful in numerous studies. However, the analysis of small datasets using RSF becomes problematic when attempting to account for complex sources of variation, and the inclusion of factors such as weather or intrinsic variation on target species' response may produce models with poor predictive ability. We compared the application of generalized linear mixed‐effects modeling (GLMM) and redundancy analysis (RDA) on Appalachian spotted skunk (Spilogale putorius putorius) den selection data at four study sites within the George Washington, Jefferson, and Monongahela National Forests, and surrounding private lands in the Appalachian Mountains of western Virginia and northeastern West Virginia. We assessed the need for the inclusion of alternative sources of variation (i.e., weather conditions and individual intrinsic variation) in addition to standard habitat attributes to better identify sources of variation in den selection. The RDA elucidated complex and opposing relationships, whereby den type use was based on reproductive status or weather condition, which were not evident in the GLMM model that relied solely on habitat measures. Our results demonstrated the importance of examining resource selection data using multivariate techniques in addition to conventional discrete choice analyses to better understand intricate habitat–species relationships, especially for small datasets. Furthermore, from our analyses, we proposed that spotted skunks are neither a true generalist nor specialist species. We introduced and define the term “conditional specialist” to represent a species that is conditionally selective of a given resource in response to one or more current environmental or intrinsic conditions.

Use of track and field training aids

High competition in athletics in theinternational sports arena stimulated theconduct of fundamental works, which addresscurrent issues of modern sport and theintroduction of various achievements ofscientific and technological progress in thetraining of athletes. But, despite the significantamount of research on the development oftheoretical and methodological foundations forthe training of athletes with the use of aids, theproblem remains largely unresolved. Thepurpose. Rationally integrate aids to optimizeand stimulate the recovery process afterexercise through targeted effects on therespiratory system, adaptation processes andspine functions in athletes involved inathletics. Material and research methods.The study was conducted on the basis of theVinnytsia Youth Sports School №1 and theVinnytsia Athletics School during thepreparatory period of 2022. The followingresearch methods were used: analysis,generalization of scientific-methodical andspecial literature, pedagogical experiment.Results. The reviewed scientific publicationsreveal sufficient arguments for thedifferentiated use of EMC, DENS and dosedtraction of the spine in the training process.After conducting a pedagogical experiment,we determined the feasibility of using athleteswho specialize in athletics training aids,depending on the period of the annual cycleand the specific tasks of the training process.Conclusions. The analysis of scientificmethodicaland special literature allowed tostudy the aspects of the use of training aids in athletics and their direct or indirect impact onimproving the skills of athletes and thedevelopment of physical and functionalfitness.

Sett Use, Density and Breeding Phenology of Badgers in Mediterranean Agro-Sylvo-Pastoral Systems.

Simple SummaryUnderstanding carnivores social structure variation is pivotal for properly addressing conservation challenges and solutions. The European badgers is a social carnivore for which most of the available information regarding how this species is socially organized derives from central west populations. This article describes the group composition, den use patterns and breeding phenology of a Mediterranean population of badgers. We showed that badger live in low density, in relatively small groups, composed by 2–4 adult animals and ca. 2 cubs, born in winter. These patterns, representing a variation of what was described for other populations, show that badgers take advantage of the landscape context, where human-related resources and mild environmental conditions allow badger to reach higher densities than in many southern populations, and to reproduce earlier than their northern counterparts.Carnivores social organization varies widely, from strongly social to solitary predators. European badgers are facultative social carnivores that also shows a geographical variation in social structure. These patterns derive mainly from central/west European regions, with an under-representation of Mediterranean populations that face different conservation challenges, especially regarding group composition, sett use patterns and breeding phenology. We addressed these traits topics for a population inhabiting a Portuguese agro-silvo-pastoral system. Based on monthly monitoring of 34 setts and continuous camera-trapping surveys of 12, we showed that setts surrounded by diversified vegetation and located in sandy sites are more used, a pattern probably linked to food availability and ease of sett excavation and maintenance, respectively. Badgers followed a general pattern regarding group size (2–4 adults), but showed an intermediate population density (0.49–0.73 badgers/km2), with values higher than those estimated for other Mediterranean environments, but lower than for central-western populations. This, together with the breeding (November/January) and cub emergence (1.8 cubs/sett; March/April) periods, indicates an ecological adaptation to the landscape context, where human-related resources and mild environmental conditions allow badger to reach higher densities than in many southern populations, and to reproduce earlier than their northern counterparts.

An experimental assessment of social tolerance and den ecology in a high-density octopus population

Long held notions of the universally asocial octopus are being challenged due to the identification of high-density and interacting octopus populations in Australia, Indonesia, Japan and the deep sea. This study experimentally assessed the social tolerance and presence of potential prey items of Caribbean reef octopus, Octopus briareus, in a tropical marine lake (25°21′40″N, 76°30′40″W) on the island of Eleuthera, The Bahamas, by deploying artificial dens in multi-den groups or ‘units’ in the months of May and June 2019. Fifteen octopus were observed occupying dens (n = 100), resulting in 13 den units being occupied (n = 40). Two examples of adjacent occupation within a single den unit were identified but with zero examples of cohabitation/den sharing. Ecological models showed den and den unit occupation was predicted to increase with depth and differ between sites. Octopus also displayed no preference for isolated or communal units but preferred isolated dens over dens adjacent to others. Additionally, 47 % of occupied dens contained bivalve or crustacean items with no epifauna on their interior surface. The lack of epifauna suggests that these items have been recently ‘cleaned’ by occupying octopus and so represent likely prey. This study presents evidence of possible antisocial den use by O. briareus, a modification of the default ‘asocial’ ignoring of conspecifics typically attributed to octopus. This is likely in response to the high population density and may imply behavioural plasticity, making this system appropriate for further scrutiny as a research location on the influence of large, insular environments on marine species.

All forests are not equal: population demographics and denning behaviour of a recovering small carnivore in human modified landscapes

Landscapes occupied by recovering carnivore populations in Europe are highly modified by human activity. It is unclear how recovering predators will adapt and sustain populations in highly altered landscapes, with most existing research focused on large carnivores. To address this we contrast population demographics and denning behaviour of a small carnivore, the pine marten Martes martes, in a semi‐natural wooded landscape and a human‐modified landscape with limited forest cover composed of conifer plantation, using radio‐telemetry on 20 free‐ranging individuals in Northern Ireland. In the semi‐natural landscape, martens selected old growth, native forest making almost exclusive use of arboreal dens in living trees and standing deadwood. Martens persisted in the human‐modified landscape but with lower population density and recruitment, with a male‐biased sex ratio. In the human‐modified landscape martens denned in marginal habitats such as scrub, heath and property boundaries, while making use of subterranean or man‐made structures for dens in response to a lack of above ground denning opportunities. We demonstrate landscape change‐induced differences in behaviour and population structure in a recovering carnivore. The results highlight the importance of evaluating the availability of denning sites in carnivore conservation and provide valuable management considerations, key to mitigating human–wildlife conflict as carnivores continue to recover and recolonise Europe.

Room without a view-Den excavation in relation to body size in brown bears.

Hibernation is an adaptive strategy to survive harsh winter conditions and food shortage. The use of well‐insulated winter dens helps animals minimize energy loss during hibernation. Brown bears (Ursus arctos) commonly use excavated dens for hibernation. Physical attributes of excavated dens are expected to impact the bear's heat retention and energy conservation. The objective of this study was to examine the determinants of cavity size of excavated dens and the impact of physical attributes of excavated dens on energy conservation in hibernating bears, hypothesizing that bears excavate dens in a way to minimize heat loss and optimize energy conservation during hibernation. We predicted that den cavity size would be determined by the bear's body size and that older bears would excavate better‐fitting cavities to minimize heat loss, due to their previous experience. We further predicted that physical attributes of excavated dens would affect the bears’ posthibernation body condition. Our results revealed that bears excavated a den cavity in relation to their body size, regardless of sex, and that older bears tended to excavate better‐fitting den cavities compared to young bears, as we expected. Older bears excavated better‐fitting den cavities, suggesting a potentially experience‐based shift with age in den‐excavation behavior and an optimum cavity size relative to a bear's body size. Our key finding is that insulation of excavated dens provided by wall/rood thickness and bedding materials had a significant positive effect on bears’ posthibernation body condition. We believe that our study provides new insight into how not only the quality of denning habitat, but also the quality of dens may affect hibernating animals, by presenting a potential adaptive aspect of den preparation (age effect on efficiency in den excavation) and effect of den attributes on the posthibernation body condition of brown bears.

Personality in Zoo-Hatched Blanding’s Turtles Affects Behavior and Survival After Reintroduction Into the Wild

Reintroduction programs in which captive-bred or reared animals are released into natural habitats are considered a key approach for conservation; however, success rates have generally been low. Accounting for factors that enable individual animals to have a greater chance of survival can not only improve overall conservation outcomes but can also impact the welfare of the individual animals involved. One such factor may be individual personality, and personality research is a growing field. We designed a project to ascertain the presence of personality traits in Blanding’s turtles (Emydoidea blandingii), a species of special concern in the state of Michigan, and to assess potential links between traits and post-release success. As hypothesized, the Blanding’s turtles in this study displayed behavioral responses to modified open field tests indicative of distinct personality traits: exploration, boldness, and aggression. Additionally, the personality traits were correlated differently with survival and behavior patterns when the turtles were released into the Shiawassee National Wildlife Refuge. More exploratory turtles had higher survival rates, while neither boldness nor aggression was related to survival. Exploratory turtles were also more likely to travel longer distances after release. The use of muskrat dens was related to increased survival, and both bolder and more exploratory turtles made higher use of this feature. Exploratory and aggressive turtles were found basking outside of water more often, while bold turtles were more likely to be found at the water surface. Both these basking behaviors may increase the risk of predation and may be reflective of a trade-off between the risk and behaviors related to physiological health. Understanding how personality affects behavior and survival post-release can be a critical tool for improving reintroduction success. Zoo animal welfare scientists and practitioners can implement approaches that improve the welfare of individuals within the context of conservation initiatives.

Den‐site characteristics and selection by brown bears (Ursus arctos) in the central Brooks Range of Alaska

AbstractSelection and use of dens is a critical behavioral adaption of bears (Ursus spp.) to survive extended periods of resource limitation. We analyzed selection of den sites by brown bears (Ursus arctos) in an arctic montane environment from 2014 to 2017. We used GPS data from 51 instrumented bears to physically locate, identify, and describe den sites (n = 33) and to quantitatively model the selection of denning habitat (n = 65 dens over 3 yr). We conducted an analysis of den‐site selection at the home range (third order) scale using variables describing topographic, vegetative, and spatially‐explicit fish and wildlife models. We hypothesized four main factors influence den‐site selection by brown bears: (1) physiography, (2) proximity to food resources, (3) thermal insulation, and (4) den‐area fidelity. We used kernel density estimates to define space use and conditional logistic regression to estimate den selection within individual home ranges. Brown bears selected den sites on steep slopes (>31°) with high snow load potential near their previously used den site. Our results supported our hypothesis that den selection by brown bears was related to thermal insulation, structural stability, drainage, and den‐area fidelity.

Dynamic electroneurostimulation in the prevention of broncho-pulmonary complications with children of the first year of life suffering from congenital heart diseases in the early post-operating period

The purpose of the study is to substantiate the use of dynamic electronic neurostimulation as a means of preventing broncho-pulmonary complications with children of the first year of life with congenital heart disease in the early postoperative period.
 Material and methods. There have been observed 82 children operated on congenital heart disease at an average age of 7.6 2.0 months old. By simple randomization, the patients were divided into two groups. Children who received the dynamic electronic neurostimulation procedure from the first day against the background of basic drug therapy were in the 1st group (40 people). The 2nd group (42 people) included patients who were treated only with basic medication.
 Results. The result analysis of the study showed a statistically significant effect in the use of dynamic electronic neurostimulation compared to the control group. By evaluating the length of the patients stay in hospital after the operative treatment, significant differences have also been obtained. Thus, the patients in the control group stayed in the unit for an average of 14.6 0.3 days, while the patients in the group where dynamic electronic neurostimulation was used in combination with basic therapy had a hospitalization period of 13.4 0.4 days (p 0.05). The use of DENS allowed to reduce the frequency of complications associated with the bronchopulmonary system starting from 34 days of the postoperative period. Thus, in the control group, 5 (11%) children showed pneumonia, 13 (30%) showed atelectasis or dystelectasis, 23 (55%) showed tracheobronchitis, while in the main group 2 (5%), 6 (15%) and 11 (27.5%) children, respectively.
 Conclusion. The obtained results of the work show the expediency of including dynamic electronic neurostimulation in the complex of medical and rehabilitation measures in early post-operative period with infants suffering from congenital heart disease.

Badger setts provide thermal refugia, buffering changeable surface weather conditions

Den use can be crucial in buffering environmental conditions and especially to provide an insulated environment for raising altricial young. Through Sept-Dec 2016 we monitored temperature and humidity at 11 badger setts (burrow systems), using thermal probes inserted over 4–13 sett entrances to a depth of ca. 2 m, supplemented by continuous daily logging at one entrance per sett. Setts were cooler than exterior conditions Sept-Oct, and warmer than exterior conditions Nov-Dec. Setts cooled down when badgers left them to forage by night, and warmed up when badgers occupied them by day. Soil type and aspect also influenced sett temperature. Sett temperature did not affect the weight or body-condition of either adults or maturing cubs in autumn. However, cubs born into setts that were relatively warmer through the preceding autumn-winter were heavier in the following spring than contemporaries born in cooler setts (badgers exhibit delayed implantation), and so warmer setts might benefit early cub growth. We posit that sett quality may be important in providing badgers with a stable thermal refuge from variable weather conditions. More broadly, den use may buffer climate change effects for many fossorial carnivore species.