Staying cool in a changing landscape: the influence of maximum daily ambient temperature on grizzly bear habitat selection

Pigeon, Karine E.; Cardinal, Étienne; Stenhouse, Gordon B.; Côté, Steeve D.

doi:10.1007/s00442-016-3630-5

Cited by 39 publications

(37 citation statements)

References 74 publications

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“…Fine‐scale climatic measurements can help identify thermal refuges overlooked by large‐scale modelling approaches, but an organism's size, mobility and perceptions will influence the scale or scales at which individuals respond to the thermal landscape (Hannah et al., ; Kotliar & Wiens, ). For example, Landsat imagery (30‐m resolution) has been used to estimate values of habitat structure in evaluations of thermal quality for moose Alces alces (Olson, Windels, Fulton, & Moen, ) and grizzly bears Ursos arctos (Pigeon, Cardinal, Stenhouse, & Cȏté, ), but such large‐bodied and mobile organisms perceive thermal heterogeneity differently than smaller species. Our results reveal that even modest changes in habitat structure can result in attenuated thermal environments across small spatial scales.…”

Section: Discussionmentioning

confidence: 99%

“…Fine-scale climatic measurements can help identify thermal refuges overlooked by largescale modelling approaches, but an organism's size, mobility and perceptions will influence the scale or scales at which individuals respond to the thermal landscape (Hannah et al, 2014;Kotliar & Wiens, 1990). For example, Landsat imagery (30-m resolution) has been used to estimate values of habitat structure in evaluations of thermal quality for moose Alces alces (Olson, Windels, Fulton, & Moen, 2014) and grizzly bears Ursos arctos (Pigeon, Cardinal, Stenhouse, & Cȏté, 2016) (Kearney et al, 2011;Porter & Kearney, 2009). For small mammals at both of our sites, T max during summer frequently exceeded the likely upper critical temperature in all three habitat types, but it was colder than the expected thermoneutral zone during winter (Araujo et al, 2013).…”

Section: Discussionmentioning

confidence: 99%

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Habitat structure modifies microclimate: An approach for mapping fine‐scale thermal refuge

et al. 2018

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Contemporary techniques predicting habitat suitability under climate change projections often underestimate availability of thermal refuges. Habitat structure contributes to thermal heterogeneity at a variety of spatial scales, but quantifying microclimates at organism‐relevant resolutions remains a challenge. Landscapes that appear homogeneous at large scales may offer patchily distributed thermal refuges at finer scales. We quantified the relationship between vegetation structure and the thermal environment at a scale relevant to small, terrestrial animals using a new approach for mapping fine‐scale thermal heterogeneity. We expected that vegetation would create attenuated microclimates and that the influence of vegetation structure would vary seasonally. We measured shrub volume, horizontal cover and operative temperature (Te) in a sagebrush‐steppe habitat in Idaho, USA, at 534 microsites across two study sites of c. 1 km2 each. We modelled relationships between habitat structure and both mean daily maximum temperature (T¯max) and mean diurnal temperature range (italicDTR¯) for each study site during summer and winter. Aerial imagery from unmanned aerial systems was used to estimate shrub volume and canopy cover at 1‐m resolution, and we applied the best fit model to map thermal heterogeneity across broader extents. Increasing shrub volume and cover was associated with lower T¯max and italicDTR¯, but strengths of the relationships differed between study sites. There was considerable heterogeneity in availability of thermal refuges across sagebrush‐steppe rangelands that have traditionally been considered relatively homogeneous. This technique can help ecologists and land managers identify critical thermal refuges that large‐scale climate modelling can overlook and thus contribute to an understanding of animal–habitat relationships under changing climates and land uses.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Habitat structure modifies microclimate: An approach for mapping fine‐scale thermal refuge

et al. 2018

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“…For example, neither our findings, nor studies by Selås () and Selås et al () explicitly tested interactive effects between weather covariates and forest stand characteristics (Kardell , Hertel et al ). Older forests buffer temperature variation more than more open habitats, like clearcuts, where temperature amplitudes are higher (Pigeon et al , Supplementary material Appendix 2 Fig. A10).…”

Section: Discussionmentioning

confidence: 99%

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

Hertel

Bischof

Langval

et al. 2017

Oikos

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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 longterm 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.

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“…Similarly, brown bears in British Columbia, Canada, did not reduce their general or diurnal activity in response to increasing maximum daily temperature (McLellan and McLellan ), even though temperatures were warmer (20.4–40.1°C) than in our study area (17.4–21°C). Conversely, Pigeon et al () reported that brown bears in Alberta, Canada, where temperatures are similar to Sweden, adjusted their habitat selection and avoided clearcuts, a habitat with potentially high food availability, during the hottest part of the days. For our study area, Ordiz et al () suggested that bears primarily adjust their habitat use to avoid humans, rather than in response to warm temperatures.…”

Section: Discussionmentioning

confidence: 99%

Fluctuating mast production does not drive Scandinavian brown bear behavior

et al. 2018

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Bears often rely on soft or hard mast during fall hyperphagia when they increase body mass in preparation for winter hibernation. Studies of North American and Japanese bear populations suggest they respond to years of mast crop failure by increasing movement rates and roaming farther, with an increase in human–wildlife conflicts. In southcentral Sweden, brown bears (Ursus arctos) primarily feed on bilberry (Vaccinium myrtillus) and lingonberry (V. vitis‐idaea) during hyperphagia. We hypothesized that berry production affects movement, activity, and space use behaviors of bears in Sweden, which have the potential to increase human–bear encounters. We tested whether seasonal activity patterns, human settlement visits, and clearcut selection ratios were affected by bilberry and lingonberry productivity between 2007 and 2017 with linear and generalized linear mixed effect models. Contrary to our expectations, we did not find that bears moved more or maintained larger home ranges in years of low berry production. Bears were slightly more active in years of higher bilberry production, but variation in behavior was primarily explained by demographic group and individual differences. Bears rarely visited human settlements and the number of visits did not increase in relation to shortage of natural foods. Likewise, population‐level selection for clearcuts was unrelated to berry production but reflected a differential food search behavior in the 2 peak berry seasons, with higher clearcut selection ratios during the lingonberry season. Only 12 bears regularly used agricultural fields, which were too few to relate field visits to berry production, but all bears visited fields more often during the later lingonberry season. We suggest that weaker fluctuations in berry production, a continuous spatial distribution of berries, and an apparent absence of forage‐limiting exploitative intra‐ or interspecific competition contribute to brown bears in Scandinavia being less food limited than bears in North America or Japan, which might help to explain the low number of human–bear conflicts in Sweden. Factors potentially influencing encounters and actual or perceived conflict between bears and humans differ among populations because of a different distribution of natural and non‐natural food resources or differences in the magnitude of variation in food abundance among years. These data are important to consider when communicating causes of human‐wildlife conflicts to the public. © 2018 The Wildlife Society.

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Staying cool in a changing landscape: the influence of maximum daily ambient temperature on grizzly bear habitat selection

Cited by 39 publications

References 74 publications

Habitat structure modifies microclimate: An approach for mapping fine‐scale thermal refuge

Habitat structure modifies microclimate: An approach for mapping fine‐scale thermal refuge

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

Fluctuating mast production does not drive Scandinavian brown bear behavior

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