Brown bear circadian behavior reveals human environmental encroachment

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 30 min. 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.