Ultimate and proximate mechanisms underlying the occurrence of bears close to human settlements: review and management implications

Large carnivores (LCs), such as bears (Ursidae), are commonly believed to occur near human settlements because they have a learned tolerance of humans (human habituation) and because they associate humans with accessible high-quality foods (food conditioning). Young bears and females with cubs are often overrepresented among problem' bears near settlements. We review the mechanisms underlying the occurrence of brown and black bears (Ursus arctos, Ursus americanus, Ursus thibetanus) near settlements, and consider four hypotheses designed to separate ultimate and proximate mechanisms. Increased occurrence of bears near people or settlements can be explained by (i) the human habituation hypothesis; increased use of human-derived foods can be explained by (ii) the food-conditioning hypothesis. However, both mechanisms are proximate, because they can only apply if bears have earlier experience of people and/or human-derived food. A lack of human experience can explain the increased occurrence of younger bears near people or settlements: (iii) the naivety hypothesis. This is a proximate mechanism, because movements of naive bears are typically triggered by aggression and/or competition among conspecifics. We conclude that the disproportionate occurrence of bears in certain sex, age and reproductive classes near people or settlements can only be explained by predation avoidance and/or interference competition, i.e. by (iv) the despotic distribution hypothesis. Therefore, a despotic distribution must be an ultimate mechanism causing the proximate mechanisms of habituation or conditioning. Thus, bears using settlements as predation refuges should not be considered unnatural', but rather as exhibiting an adaptive behaviour, because of the despotic distribution among conspecifics. Management of LCs includes attractant management, to counteract food conditioning, but failure to consider despotic behaviour among conspecifics may lead to treating only the symptom, e.g. habituation or conditioning. The ultimate cause of attraction to specific settlements may be identified by considering the type of bear involved; the occurrence of large solitary bears near settlements suggests attractive habitat or food shortage in remote areas, whereas subadults and females with cubs suggest lower-quality habitat.