Social behaviour of black bears at a garbage dump in Jasper National Park

by Stephen Herrero, faculty of environmental design, Univ. of Calgary, Calgary, Alberta

A minimum population of 34 black bears (Ursus americanus) visiting and feeding at the town dump in Jasper National Park, Alberta, were observed for over 750 hours on 141 days in 1968. Females with young of the year visited the dump more than any other group. Their average litter size of 2.67 for regular dump visitors suggests that food from the dump contributed
to reproductives uccess. Social interactions between bears were characterized by tolerance, avoidance and spacing, but we did observe 141 intraspecifica gonistici nteractions. In 89 out of 91 agonistici nteractions,f emales with young of the year dominated all other age/sex classes, including adult males. These females, even when not with their young, used agonistic behaviour to maintain an individuald istanceo f 3 to 30 m. Twelve posturala nd 4 vocal componentso f the agonistic repertoires are described and frequency of use is given for each identifiedb ear. Agonistics ignalsw ere stereotypedb ut not invariant;p hysicalc ontact was rare. Agonistic interactions were more frequente arly in the season than later. The dump was visited by 7,500 to 10,000 tourists; despite hundreds of close approaches, including 57 situations in which people threw rocks or chased bears, a bear never struck, bit, or
touched a person. Bears on 15 such occasions directed agonistic signals toward people; these were similar to signals used in intraspecific encounters. Subadults and females with their young climbed trees, where they appeared to find safety from harassment.Bears in trees were seen nursing, playing, sleeping, sheltering, relaxing, or cooling. The dump offered a food source which was concentrated high-quality predictable, and prolonged in time. Bearse xploitedt his resourceb y formings ocial aggregationst, olerating
other bears at shorter distances when at the dump than when away.

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