Behavioural differences between locally recruiting and dispersing gray squirrels, Sciurus carolinensis

Abstract

We tested the hypothesis that recruitment into a resident population involved the selection of an independently defined behavioural type of animal. Gray squirrels were captured in or shortly after leaving their nests, held in the laboratory in a similar manner, and their behavioural profiles and other properties were determined. The following spring, they were released into the area where most were captured and which we virtually emptied of residents prior to the release. Sixty days following the release, 64% (18/28) of the squirrels had dispersed, most before 10 days, and the remainder recruited and became residents. From the laboratory tests, local recruits compared with dispersers were on average more aggressive. There were no clear differences between the two types in mass, tail length, and sex ratio. All were sexually immature. Recruits were more active than dispersers in December, and activity of both appeared to decline from November to April. Proportionately more of the pepper morph recruited than of the black and gray morphs. There appear to be genetic behavioural and colour morph differences among squirrels that affect or are linked to their local recruitment or dispersal and population regulation.