Spatial and temporal interactions between female American black bears in mixed forests of eastern Canada

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Few studies have examined in detail the spacing patterns of American black bears (Ursus americanus), especially populations protected from hunting. We radio-tracked bears between 1990 and 1992 in La Mauricie National Park in southern Quebec to study their social interactions. We measured the zone of overlap between home-range core areas and evaluated the spatial and temporal use of the overlap zones for 12 adult females radio-tracked during 1992. The proportion of overlap between the core areas used by 22 pairs of females was variable but low (14.2 ± 17.6% (mean ± SD)). This proportion did not differ (p > 0.05) from that obtained from a random distribution of home ranges (17.1 ± 17.1%). For 12 (55%) of 22 pairs with overlapping core areas, at least one of the females was significantly attracted by the overlap zone, whereas one of the females of another pair significantly avoided it. Significant simultaneous use of the overlap zone was observed for 7 pairs and significant temporal avoidance of the overlap zone was noted for 1 pair. The overlap zone contained a significantly higher proportion of food-producing cover types (maple–beech and early-successional stands) than the overall study area. Our results indicate that although most females did not share a large proportion of their core area with their neighbours, the overlap zone was used intensively for foraging by more than one bear, often simultaneously. Some aggressive behaviours were noted when bears were seen foraging simultaneously in the same area. We discuss the influence of spatial and temporal interactions on the regulation of this unhunted population.