Hibernation is an adaptation that helps many animals to conserve energy during food shortage in winter. Brown bears double their fat depots during summer and use these stored lipids during ...hibernation. Although bears seasonally become obese, they remain metabolically healthy. We analyzed the microbiota of free-ranging brown bears during their active phase and hibernation. Compared to the active phase, hibernation microbiota had reduced diversity, reduced levels of Firmicutes and Actinobacteria, and increased levels of Bacteroidetes. Several metabolites involved in lipid metabolism, including triglycerides, cholesterol, and bile acids, were also affected by hibernation. Transplantation of the bear microbiota from summer and winter to germ-free mice transferred some of the seasonal metabolic features and demonstrated that the summer microbiota promoted adiposity without impairing glucose tolerance, suggesting that seasonal variation in the microbiota may contribute to host energy metabolism in the hibernating brown bear.
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•Bear microbiota composition differs seasonally between hibernation and active phase•Blood metabolites differ seasonally in the brown bear•The bear gut microbiota promote energy storage during summer
Sommer et al. show that the microbiota and serum metabolites in brown bears differ seasonally between hibernation and active phase. Colonization of mice with a bear microbiota promoted increased adiposity. These findings suggest that seasonal microbiota variation may contribute to metabolism of the hibernating brown bear.
Abstract
Brown bears (
Ursus arctos
) hibernate for 5–6 months during winter, but despite kidney insufficiency, dyslipidemia and inactivity they do not seem to develop atherosclerosis or ...cardiovascular disease (CVD). IgM antibodies against phosphorylcholine (anti-PC) and malondialdehyde (anti-MDA) are associated with less atherosclerosis, CVD and mortality in uremia in humans and have anti-inflammatory and other potentially protective properties. PC but not MDA is exposed on different types of microorganisms. We determine anti-PC and anti-MDA in brown bears in summer and winter. Paired serum samples from 12 free ranging Swedish brown bears were collected during hibernation in winter and during active state in summer and analyzed for IgM, IgG, IgG1/2 and IgA anti-PC and anti-MDA by enzyme linked immunosorbent assay (ELISA). When determined as arbitrary units (median set at 100 for summer samples), significantly raised levels were observed in winter for anti-PC subclasses and isotypes, and for IgA anti-PC the difference was striking; 100 IQR (85.9–107.9) vs 782.3, IQR (422.8–1586.0; p < 0.001). In contrast, subclasses and isotypes of anti-MDA were significantly lower in winter except IgA anti-MDA, which was not detectable. Anti-PCs are significantly raised during hibernation in brown bears; especially IgA anti-PC was strikingly high. In contrast, anti-MDA titers was decreased during hibernation. Our observation may represent natural immunization with microorganisms during a vulnerable period and could have therapeutic implications for prevention of atherosclerosis.
The ongoing recovery of terrestrial large carnivores in North America and Europe is accompanied by intense controversy. On the one hand, reestablishment of large carnivores entails a recovery of ...their most important ecological role, predation. On the other hand, societies are struggling to relearn how to live with apex predators that kill livestock, compete for game species, and occasionally injure or kill people. Those responsible for managing these species and mitigating conflict often lack fundamental information due to a long-standing challenge in ecology: How do we draw robust population-level inferences for elusive animals spread over immense areas? Here we showcase the application of an effective tool for spatially explicit tracking and forecasting of wildlife population dynamics at scales that are relevant to management and conservation. We analyzed the world’s largest dataset on carnivores comprising more than 35,000 noninvasively obtained DNA samples from over 6,000 individual brown bears (Ursus arctos), gray wolves (Canis lupus), and wolverines (Gulo gulo). Our analyses took into account that not all individuals are detected and, even if detected, their fates are not always known. We show unequivocal quantitative evidence of large carnivore recovery in northern Europe, juxtaposed with the finding that humans are the single-most important factor driving the dynamics of these apex predators. We present maps and forecasts of the spatiotemporal dynamics of large carnivore populations, transcending national boundaries and management regimes.
Harvest regulations commonly attenuate the consequences of hunting on specific segments of a population. However, regulations may not protect individuals from non‐lethal effects of hunting and their ...consequences remain poorly understood. In this study, we compared the movement rates of Scandinavian brown bears (Ursus arctos, n = 47) across spatiotemporal variations in risk in relation to the onset of bear hunting. We tested two alternative hypotheses based on whether behavioural responses to hunting involve hiding or escaping. If bears try to reduce risk exposure by avoiding being detected by hunters, we expect individuals from all demographic groups to reduce their movement rate during the hunting season. On the other hand, if bears avoid hunters by escaping, we expect them to increase their movement rate in order to leave high‐risk areas faster. We found an increased movement rate in females accompanied by dependent offspring during the morning hours of the bear hunting season, a general decrease in movement rate in adult lone females, and no changes in males and subadult females. The increased movement rate that we observed in females with dependant offspring during the hunting season was likely an antipredator response because it only occurred in areas located closer to roads, whereas the decreased movement rate in lone females could be either part of seasonal activity patterns or be associated with an increased selection for better concealment. Our study suggests that female brown bears accompanied by offspring likely move faster in high‐risk areas to minimize risk exposure as well as the costly trade‐offs (i.e. time spent foraging vs. time spent hiding) typically associated with anti‐predator tactics that involve changes in resource selection. Our study also highlights the importance of modelling fine‐scale spatiotemporal variations in risk to adequately capture the complexity in behavioural responses caused by human activities in wildlife.
In this study, we investigated the movement behaviour of brown bears in response to roads and human disturbances by using linear mixed‐effect models. We found that females with dependant offspring increase their movement speed when located close to roads during the bear hunting season.
Factors for initiating hibernation are unknown, but the condition shares some metabolic similarities with consciousness/sleep, which has been associated with n-3 fatty acids in humans. We ...investigated plasma phospholipid fatty acid profiles during hibernation and summer in free-ranging brown bears (Ursus arctos) and in captive garden dormice (Eliomys quercinus) contrasting in their hibernation patterns. The dormice received three different dietary fatty acid concentrations of linoleic acid (LA) (19%, 36% and 53%), with correspondingly decreased alpha-linolenic acid (ALA) (32%, 17% and 1.4%). Saturated and monounsaturated fatty acids showed small differences between summer and hibernation in both species. The dormice diet influenced n-6 fatty acids and eicosapentaenoic acid (EPA) concentrations in plasma phospholipids. Consistent differences between summer and hibernation in bears and dormice were decreased ALA and EPA and marked increase of n-3 docosapentaenoic acid and a minor increase of docosahexaenoic acid in parallel with several hundred percent increase of the activity index of elongase ELOVL2 transforming C20-22 fatty acids. The highest LA supply was unexpectantly associated with the highest transformation of the n-3 fatty acids. Similar fatty acid patterns in two contrasting hibernating species indicates a link to the hibernation phenotype and requires further studies in relation to consciousness and metabolism.
Obligate herbivores dominate studies of the effects of climate change on mammals, however there is limited empirical evidence for how changes in the abundance or quality of plant food affect ...mammalian omnivores. Omnivores can exploit a range of different food resources over the course of a year, but they often rely on seasonally restricted highly nutritious fruiting bodies during critical life stages. Brown bears Ursus arctos in Sweden are dependent on berries for fattening before entering hibernation. We used a ten‐year time series to evaluate the effect of temperature and snow on annual variation in berry abundance and how this variation affected bears. We found marked interannual variation in berry production of bilberry Vaccinium myrtillus and lingonberry V. vitis‐idaea, that we could attribute in part to temperature during plant dormancy and flowering and precipitation during fruit ripening. Both, autumn weights of female bears and spring weights of yearling bears increased linearly with bilberry abundance. When bilberry abundance was low, lightweight female bears had a lower reproductive success than females in better condition. This effect vanished when food abundance was above average, indicating that lightweight females could compensate for their initial weight during good bilberry years. Our study highlights the importance of considering individuals’ dynamic responses to variation in food availability, which leave some more vulnerable to food shortage than others. Individual life‐history heterogeneity in response to resource variation likely affects long‐term population recruitment. Our findings emphasize that Scandinavian bears can be dependent on a single food resource during a critical period of the year and are therefore less resilient to environmental change than expected for an omnivore. Future climate scenarios predict ambiguous trends for weather covariates that affected crucial stages of berry phenology, preventing a clear prognosis of how climate change may affect long‐term bilberry production.
Obtaining reliable species observations is of great importance in animal ecology and wildlife conservation. An increasing number of studies use camera traps (CTs) to study wildlife communities, and ...an increasing effort is made to make better use and reuse of the large amounts of data that are produced. It is in these circumstances that it becomes paramount to correct for the species‐ and study‐specific variation in imperfect detection within CTs. We reviewed the literature and used our own experience to compile a list of factors that affect CT detection of animals. We did this within a conceptual framework of six distinct scales separating out the influences of (a) animal characteristics, (b) CT specifications, (c) CT set‐up protocols, and (d) environmental variables. We identified 40 factors that can potentially influence the detection of animals by CTs at these six scales. Many of these factors were related to only a few overarching parameters. Most of the animal characteristics scale with body mass and diet type, and most environmental characteristics differ with season or latitude such that remote sensing products like NDVI could be used as a proxy index to capture this variation. Factors that influence detection at the microsite and camera scales are probably the most important in determining CT detection of animals. The type of study and specific research question will determine which factors should be corrected. Corrections can be done by directly adjusting the CT metric of interest or by using covariates in a statistical framework. Our conceptual framework can be used to design better CT studies and help when analyzing CT data. Furthermore, it provides an overview of which factors should be reported in CT studies to make them repeatable, comparable, and their data reusable. This should greatly improve the possibilities for global scale analyses of (reused) CT data.
Detection of animals by camera traps is determined by processes at different scales. These need to be included in study design and analysis of camera trapping data. Camera trapping data can only be reused for future studies when factors influencing detection are properly reported.
Abstract Background The wild boar ( Sus scrofa ) was extinct in Sweden when a few animals established in the 1970s. Over the past 35 years, the species has made a substantial comeback. In this paper, ...we analyse wild boar population growth using three indices of population size. We also map the legislative decisions and research prompted by the expanding population. We discuss to what extent, in the eyes of the state, the view of wild boar and the management focus has shifted over time, from a perceived pest (eradication) to scarce (conservation), overabundant (reduction/control) or somewhere in between (sustainable management). Results Wild boar harvest started in the early 1990s with a few hundred animals annually and peaked at 161,000 in 2020/2021. The distribution now comprises most of southern Sweden. Analyses of harvest and traffic accidents involving wild boar showed that the population grew exponentially until 2010/2011, after which the increase levelled off. Thus, logistic growth models showed the best fit for the full study period. We recorded 38 legislative decisions or commissions to government agencies regarding wild boar. The first decision in 1981 was to eradicate the free-ranging population. In 1987 however, the parliament decided that wild boar is native to Sweden and should be allowed in restricted extent. Later decisions mainly concerned hunting regulations and hunting methods as direct means to increase harvest and regulate the population. Another topic, increasing in importance over time, was to facilitate the use of wild boar meat to indirectly stimulate harvest. A local outbreak of African swine fever in 2023 necessitated a stamping out strategy in the affected area. We found 44 scientific papers regarding the present free-ranging population. Topics include movements and feeding patterns, hunting, reproduction, and population development. Conclusions The state historically regarded wild boar as a pest to be eradicated. This changed with the decision that wild boar should be allowed in restricted extent, suggesting a conservation approach. In response to population growth, the focus shifted to means facilitating sustainable management and, lately, reducing growth. The story of wild boar in Sweden illustrates attempts to mitigate conflicts and balance interests in wildlife management.
•Many large carnivores show behavioral plasticity in their daily movement patterns.•Whether environmental or anthropogenic cues cause such variation is not clear yet.•Brown bears moved more in the ...nocturnal and twilight hours in areas with higher road density.•Human proximity, a proxy of human density around bears, had no effect on their behavior.•Minimizing disturbance on carnivore behavior should be included in management plans.
Large carnivores adjust their daily movement patterns in response to environmental factors and/or human disturbance, and often respond differently across their distribution range. Whether such behavioral plasticity is due to environmental or anthropogenic factors has not yet been fully clarified. Beyond large carnivore conservation and management, understanding behavioral changes in the movement patterns of these elusive species may prove useful to evaluate anthropogenic influences on ecosystems. We used 696 318 GPS locations from 105 radio-collared brown bears in 3 study areas in Sweden to construct daily bear movement patterns, calculating the distance traveled by the bears every 30min. We used a Bayesian approach to analyze whether human and/or road density around bear locations could explain observed differences in bear movement patterns among the areas. Proximity to settlements, a proxy of the generally low human density in Scandinavian bear range, did not influence circadian bear movements. However, bears moved most in the nocturnal and twilight hours and less during daytime in areas with higher road density, compared to roadless areas. Human-caused behavioral changes in large carnivores may have potential ecosystem-level consequences, given the key ecological role that these species can play in ecosystems. Limiting the creation and use of roads is necessary to maintain large carnivore distribution ranges and movement corridors, reduce human-caused mortality, and minimize human-induced disturbance that modifies carnivore behavior.
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