The effects of increasing human activity on brown bear use of an Alaskan river Original Research Article

We assessed the effects of increasing human activity on brown bear Ursus arctos use of a salmon spawning stream by comparing observations (865 h) collected 1988–1990 to those (293 h) from 1992 when human activities extended a week later into the fall feeding period (26 August–12 October). We classified individual adult bears according to their tolerance of people as ‘habituated’, or ‘non-habituated’; sub-adults were considered a third behavioural class. In 1992, non-habituated adults (n = 14 of 22 total adults) reduced their activity in apparent response to an extended lodge season, by delaying their use of the river by 17 days. In contrast, habituated adult bear activity remained similar among years, and sub-adult activity increased > four-fold in 1992. We suggest that the human-induced decrease in non-habituated adult activity may have allowed the increased levels of sub-adult activity.