Sex-biased dispersal in eastern chipmunks, Tamias striatus

I investigated the effect of male mate competition and inbreeding avoidance on natal dispersal of chipmunks by longitudinally monitoring known individ uals from 1986 to 1990. Natal males exhibited greater absolute and effectiv e dispersal distances but dispersed at the same proportion as natal females . Recruitment of juvenile males was negatively affected by density of resid ent males, but there was no evidence of local mate competition among male k in. Analysis of the spatial distribution of neighbors showed that natal mal es settled farther from their mothers than did their female siblings and fa rther than unrelated juvenile males. In addition, mothers apparently tolera ted daughters as close neighbors and occasionally shared den sites with gra ndprogeny. Sexually mature males were never neighbors of their mothers and were never observed at maternal mating bouts. Males may disperse to improve reproductive opportunities by avoiding competition with resident males, an d by increasing access to unrelated females. Maternal tolerance of daughter s but not sons may result in the close affiliation between mothers and daug hters, and indirectly contribute to dispersal of natal males. Hence male-bi ased dispersal could be a consequence of mate competition and maternal avoi dance of incestuous matings.