THE EFFECTS OF INCREASING HUMAN ACTIVITY ON BROWN BEAR USE OF AN ALASKAN RIVER

We assessed the effects of increasing human activity on brown bear Urs us arctos use of a salmon spawning stream by comparing observations (8 65 h) collected 1988-1990 to those (293 h) from 1992 when human activi ties extended a week later into the fall feeding period (26 August-12 October). We classified individual adult bears according to their tole rance 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 t o an extended lodge season, by delaying their use of the river by 17 d ays. In contrast, habituated adult bear activity remained similar amon g years, and sub-adult activity increased >four-fold in 1992. We sugge st that the human-induced decrease in non-habituated adult activity ma y have allowed the increased levels of sub-adult activity. (C) 1997 El sevier Science Ltd.