Social organization and group formation of raccoons at the edge of their distribution

Abstract

We examined spatial arid temporal relationships of 104 raccoons (Procyon lotor) at the northern edge of their distribution to report social organization and to test hypotheses regarding the formation of coalition groups among adult male carnivores. Social tolerance among females varied among years, but adults maintained relatively exclusive home ranges (overlap ranged from 2.2% to 12.5%) that were dispersed in a uniform pattern throughout the duration of the study (Clark-Evans ratios ranging from 1.32 to 1.87, P < 0.001-0.08). Social interactions among males were more complex than previously described for low-density populations of raccoons, with most adults (approximately 80%) forming coalition groups. We identified 9 unique coalitions that had extensively overlapping home ranges and positively associated nightly movements within group members (overlap indices ranging from 85.3% to 97.3%). Coalitions maintained exclusive territories between groups (overlap indices ranging from 0% to 3.2%) and formed distinct spatial boundaries that were highly correlated with home-range boundaries of females. Male coalition groups in the order Carnivora are hypothesized to form in response to aggregations of females, but examination of our data suggests that this is not a prerequisite for their formation. We propose a dominance hierarchy where subordinate males benefit through increased likelihood of inheritance of territories, whereas dominant males benefit through increased efficiency of territorial defense. © 2008 American Society of Mammalogists.