title: Bears and berries: species-specific selective foraging on a patchily distributed food resource in a human-altered landscape.
abstract: When animals are faced with extraordinary energy-consuming 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.
  
  
  CONCLUSIONS
  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 high-return habitats for bilberries, but did not compensate for the decline in bilberries by eating more lingonberries.
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, 1430 Ås, Norway.
authors.forename: Anne G
authors.initials: AG
authors.lastname: Hertel
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, 1430 Ås, Norway.
authors.forename: Sam M J G
authors.initials: SM
authors.lastname: Steyaert
authors.affiliation: Department of Environmental and Health Sciences, Telemark University College, 3901 Porsgrunn, Norway ; Institute for Wildlife Biology and Game Management, University for Natural Resources and Life Sciences, 1180 Vienna, Austria.
authors.forename: Andreas
authors.initials: A
authors.lastname: Zedrosser
authors.affiliation: Department of Biosciences, Centre for Ecological and Evolutionary Synthesis (CEES), University of Oslo, 0316 Oslo, Norway.
authors.forename: Atle
authors.initials: A
authors.lastname: Mysterud
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, 1430 Ås, Norway.
authors.forename: Hanna K
authors.initials: HK
authors.lastname: Lodberg-Holm
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, 1430 Ås, Norway.
authors.forename: Henriette Wathne
authors.initials: HW
authors.lastname: Gelink
authors.affiliation: Swedish University of Agricultural Sciences, 90183 Umeå, Sweden.
authors.forename: Jonas
authors.initials: J
authors.lastname: Kindberg
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, 1430 Ås, Norway ; Norwegian Institute for Nature Research, 7485 Trondheim, Norway.
authors.forename: Jon E
authors.initials: JE
authors.lastname: Swenson
keywords: Bilberry; Brown bear; Lingonberry; Movement trajectories; Optimal foraging; Sugar content