Endozoochory by brown bears stimulates germination in bilberry

The understory vegetation of the Eurasian boreal forest is dominated by several ericaceous species (e.g. bilberry Vaccinium myrtillus). These species invest large amounts of energy in their sexual reproduction by producing seed-containing berries, which are apparent adaptations for endozoochory. Their seedlings are, however, almost never found in the wild, and they reproduce virtually exclusively through clones. Brown bears Ursus arctos consume enormous amounts of ericaceous berries (predominantly bilberry in central Scandinavia) during hyperphagia, and may facilitate sexual reproduction in such species. If ericaceous species would benefit from endozoochory by brown bears, one would predict that endozoochory would have no negative impacts on germination. We experimentally evaluated this prediction using germination trials under controlled conditions of bilberry seeds that were 1) extracted from brown bear feces, 2) extracted from ripe berries and 3) contained in berries. Using time-to-event analyses, we showed that passing the gut by itself did not stimulate or limit germination. However, seeds that were released from the berries germinated about one month earlier compared to seeds contained in berries. This implies that being released from a fruit, for example through endozoochory, can have a large temporal germination and growth advantage, especially in northern ecosystems a with short growing season.publishedVersio

The role of familial conflict in home range settlement and fitness of a solitary mammal

Journal of evolutionary biology Blackwell/wileyFamilial conflict, including parenteoffspring conflict (POC) and sibling competition (SC), occurs when an individual maximizes its access to a limiting resource at the expense of a related individual. The role of familial conflict for competition over space as a limited resource remains relatively unexplored. In this study, we examined how familial conflict affects natal dispersal and settlement decisions of a solitary mammal, the brown bear, Ursus arctos, and tested whether these settlement patterns covary with fitness. First, we tested whether the distance settled from the natal range was affected by aspects of POC (litter type: single versus multiple; mother's age; mother's living status) and SC (settled near versus far from the natal home range, body size). We then modelled how distance settled from the natal range influenced three measures of fitness: survival to reproduction, lifetime reproductive success and lifetime survival. In line with POC, we found that daughters settled twice as far from the natal range when their mother was alive than when she was dead. We found strong evidence for SC where in sibling pairs, the ‘near’ sister settled nearly three times closer to the natal range than her sibling. We found contradictory patterns in fitness outcomes based on settlement distance, such that females settling closer to the natal range had higher lifetime survival but were less likely to successfully wean at least one offspring. Despite survival advantages gained by settling closer to the natal range, there was no evidence that settlement distance influenced lifetime reproductive success. Fitness outcomes in this population may be influenced more by factors related to annual hunting than by familial conflict or proximity to the natal range. dispersal fitness parenteoffspring conflict reproductive success sibling competitionpublishedVersio

A human-induced landscape of fear influences foraging behavior of brown bears

Animals adapt their foraging behavior to variations in food availability and predation risk. In Sweden, brown bears (Ursus arctos) depend on a nearly continuous intake of berries, especially bilberries (Vaccinium myrtillus) during late summer and early autumn to fatten up prior to hibernation. This overlaps with the bear hunting season that starts on 21 August. Bilberry occurrence varies across space, as does human-induced mortality risk. Here, we hypothesize that brown bears select for areas with a high probability of bilberry occurrence across a boreal forest ecosystem in Sweden (H1), and that human-induced mortality risk reduces bear selection for bilberries (H2). In addition, we hypothesized that bears that survived the hunting season avoided bilberry areas associated with high risk, whereas bears that were later killed selected more strongly for berries and less against risk prior to the hunting season (H3). To evaluate our hypotheses, we used resource selection functions to contrast bear GPS relocation data (N = 35, 2012–2015) and random positions within the bearś home range with generalized linear mixed effect models against two focal variables: a map predicting bilberry occurrence and a map predicting human-induced mortality risk. We found that bears selected for areas with a high probability of bilberry occurrence (supporting H1), but avoided these areas if they were associated with and high risk of hunting mortality (supporting H2). The killed and surviving bears did not differ in their selection for bilberries, but they did differ in their selection against risk (partially supporting H3). Surviving bears strongly avoided high risk areas, whereas killed bears responded less to risk and selected for high-risk areas with a low probability of bilberry occurrence. This suggests that killed bears selected for other food sources than berries in high risk areas, which exposed them to human hunters. We conclude that bears respond to a landscape of fear during the berry season and that different foraging strategies may have a direct impact on individual mortality during the hunting season.acceptedVersio

Seasonality in Biological Rhythms in Scandinavian brown Bears

Biological rhythms, such as rhythms in activity and body temperature, are usually highly synchronized and entrained by environmental conditions, such as photoperiod. However, how the expression of these rhythms changes during hibernation, when the perception of environmental cues is limited, has not yet been fully understood for all hibernators, especially in the wild. The brown bear (Ursus arctos) in Scandinavia lives in a highly seasonal environment and adapts to harsh winter conditions by exhibiting hibernation, characterized by reduced metabolism and activity. In this study, we aimed to explore the expression of biological rhythms in activity, body temperature and heart rate of free-ranging brown bears over the annual cycle, including active, hibernation and the transition states around den entry and exit. We found that rhythms in physiology and activity are mostly synchronized and entrained by the light-dark cycle during the bears’ active state with predominantly diel and ultradian rhythms for body temperature, activity, and heart rate. However, during hibernation, rhythms in body temperature and heart rate were considerably slowed down to infradian rhythms, influenced by the amount of snow in the denning area, whereas rhythms in activity remained diel. Rhythms in the transition states when bears prepared for entering or coming out of hibernation state displayed a combination of infradian and diel rhythms, indicating the preparation of the body for the change in environmental conditions. These results reveal that brown bears adjust their biological rhythms to the seasonal environment they inhabit. Rhythms in physiology and activity show simultaneity during the active state but are partly disconnected from each other during hibernation, when bears are most sheltered from the environment.publishedVersio

Endozoochory by brown bears stimulates germination in bilberry

The understory vegetation of the Eurasian boreal forest is dominated by several ericaceous species (e.g. bilberry Vaccinium myrtillus). These species invest large amounts of energy in their sexual reproduction by producing seed-containing berries, which are apparent adaptations for endozoochory. Their seedlings are, however, almost never found in the wild, and they reproduce virtually exclusively through clones. Brown bears Ursus arctos consume enormous amounts of ericaceous berries (predominantly bilberry in central Scandinavia) during hyperphagia, and may facilitate sexual reproduction in such species. If ericaceous species would benefit from endozoochory by brown bears, one would predict that endozoochory would have no negative impacts on germination. We experimentally evaluated this prediction using germination trials under controlled conditions of bilberry seeds that were 1) extracted from brown bear feces, 2) extracted from ripe berries and 3) contained in berries. Using time-to-event analyses, we showed that passing the gut by itself did not stimulate or limit germination. However, seeds that were released from the berries germinated about one month earlier compared to seeds contained in berries. This implies that being released from a fruit, for example through endozoochory, can have a large temporal germination and growth advantage, especially in northern ecosystems a with short growing season

Endozoochory by brown bears stimulates germination in bilberry

The understory vegetation of the Eurasian boreal forest is dominated by several ericaceous species (e.g. bilberry Vaccinium myrtillus). These species invest large amounts of energy in their sexual reproduction by producing seed-containing berries, which are apparent adaptations for endozoochory. Their seedlings are, however, almost never found in the wild, and they reproduce virtually exclusively through clones. Brown bears Ursus arctos consume enormous amounts of ericaceous berries (predominantly bilberry in central Scandinavia) during hyperphagia, and may facilitate sexual reproduction in such species. If ericaceous species would benefit from endozoochory by brown bears, one would predict that endozoochory would have no negative impacts on germination. We experimentally evaluated this prediction using germination trials under controlled conditions of bilberry seeds that were 1) extracted from brown bear feces, 2) extracted from ripe berries and 3) contained in berries. Using time-to-event analyses, we showed that passing the gut by itself did not stimulate or limit germination. However, seeds that were released from the berries germinated about one month earlier compared to seeds contained in berries. This implies that being released from a fruit, for example through endozoochory, can have a large temporal germination and growth advantage, especially in northern ecosystems a with short growing season

Bears and berries: species-specific selective foraging on a patchily distributed food resource in a human-altered landscape

When animals are faced with extraordinary energyconsuming events, like hibernation, finding abundant, energy-rich food resources becomes particularly important. The profitability of food resources can vary spatially, depending on occurrence, quality, and local abundance. Here, we used the brown bear (Ursus arctos) as a model species to quantify selective foraging on berries in different habitats during hyperphagia in autumn prior to hibernation. During the peak berry season in August and September, we sampled berry occurrence, abundance, and sugar content, a proxy for quality, at locations selected by bears for foraging and at random locations in the landscape. The factors determining selection of berries were species specific across the different habitats. Compared to random locations, bears selected locations with a higher probability of occurrence and higher abundance of bilberries (Vaccinium myrtillus) and a higher probability of occurrence, but not abundance, of lingonberries (Vaccinium vitis-idaea). Crowberries (Empetrum hermaphroditum) were least available and least used. Sugar content affected the selection of lingonberries, but not of bilberries. Abundance of bilberries at random locations decreased and abundance of lingonberries increased during fall, but bears did not adjust their foraging strategy by increasing selection for lingonberries. Forestry practices had a large effect on berry occurrence and abundance, and brown bears responded by foraging most selectively in mature forests and on clearcuts. This study shows that bears are successful in navigating human-shaped forest landscapes by using areas of higher than average berry abundance in a period when abundant food intake is particularly important to increase body mass prior to hibernation. Significance statement Food resources heterogeneity, caused by spatial and temporal variation of specific foods, poses a challenge to foragers, particularly when faced with extraordinary energy-demanding events, like hibernation. Brown bears in Sweden inhabit a landscape shaped by forestry practices. Bilberries and lingonberries, the bears’ main food resources in autumn prior to hibernation, show different temporal and habitat-specific ripening patterns. We quantified the bears’ selective foraging on these berry species on clearcuts, bogs, young, and mature forests compared to random locations. Despite a temporal decline of ripe bilberries, bears used locations with a greater occurrence and abundance of bilberries, but not lingonberries. We conclude that bears successfully navigated in this heavily human-shaped landscape by selectively foraging in highreturn habitats for bilberries, but did not compensate for the decline in bilberries by eating more lingonberries.Bilberry . Brown bear . Lingonberry . Movement trajectories . Optimal foraging . Sugar contentpublishedVersio

Temporal effects of hunting on foraging behavior of an apex predator: Do bears forego foraging when risk is high?

Avoiding predators most often entails a food cost. For the Scandinavian brown bear (Ursus arctos), the hunting season coincides with the period of hyperphagia. Hunting mortality risk is not uniformly distributed throughout the day, but peaks in the early morning hours. As bears must increase mass for winter survival, they should be sensitive to temporal allocation of antipredator responses to periods of highest risk. We expected bears to reduce foraging activity at the expense of food intake in the morning hours when risk was high, but not in the afternoon, when risk was low. We used fine-scale GPS-derived activity patterns during the 2 weeks before and after the onset of the annual bear hunting season. At locations of probable foraging, we assessed abundance and sugar content, of bilberry (Vaccinium myrtillus), the most important autumn food resource for bears in this area. Bears decreased their foraging activity in the morning hours of the hunting season. Likewise, they foraged less efficiently and on poorer quality berries in the morning. Neither of our foraging measures were affected by hunting in the afternoon foraging bout, indicating that bears did not allocate antipredator behavior to times of comparably lower risk. Bears effectively responded to variation in risk on the scale of hours. This entailed a measurable foraging cost. The additive effect of reduced foraging activity, reduced forage intake, and lower quality food may result in poorer body condition upon den entry and may ultimately reduce reproductive success

Heritability of head size in a hunted large carnivore, the brown bear (Ursus arctos)

Wild animal populations experience selection pressures from both natural and anthropogenic sources. The availability of extensive pedigrees is increasing along with our ability to quantify the heritability and evolvability of phenotypic traits and thus the speed and potential for evolutionary change in wild populations. The environment may also affect gene expressions in individuals, which may in turn affect the potential of phenotypic traits to respond to selection. Knowledge about the relationship between the genetic and environmental components of phenotypic variation is particularly relevant, given ongoing anthropogenically driven global change. Using a quantitative genetic mixed model, we disentangled the genetic and environmental components of phenotypic variance in a large carnivore, the brown bear (Ursus arctos). We combined a pedigree covering ~1,500 individual bears over seven generations with location data from 413 bears, as well as data on bear density, habitat characteristics, and climatic conditions. We found a narrow‐sense heritability of 0.24 (95% CrI: 0.06–0.38) for brown bear head size, showing that the trait can respond to selection at a moderate speed. The environment contributed substantially to phenotypic variation, and we partitioned this into birth year (5.9%), nonadditive among‐individual genetic (15.0%), and residual (50.4%) environmental effects. Brown bear head circumference showed an evolvability of 0.2%, which can generate large changes in the trait mean over some hundreds of generations. Our study is among the first to quantify heritability of a trait in a hunted large carnivore population. Such knowledge about the degree to which species experiencing hunting can respond to selection is crucial for conservation and to make informed management decisions. We show that including important environmental variables when analyzing heritability is key to understanding the dynamics of the evolutionary potential of phenotypic traits.publishedVersio

Berry production drives bottom – up effects on body mass and reproductive success in an omnivore

Obligate herbivores dominate studies of the eff ects of climate change on mammals, however there is limited empirical evidence for how changes in the abundance or quality of plant food aff ect mammalian omnivores. Omnivores can exploit a range of diff erent 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 eff ect of temperature and snow on annual variation in berry abundance and how this variation aff ected 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. Th is eff ect 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 aff ects long-term population recruitment. Our fi ndings 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 aff ected crucial stages of berry phenology, preventing a clear prognosis of how climate change may aff ect long-term bilberry production