Social organization in woodchucks (Marmota monax) and its relationship to growing season

Among sciurids, delayed dispersal may result from slow rates of maturation associated with short growing seasons and large body mass. However, woodchucks (Marmota monax) experience a range of ecological conditions and display behavioral flexibility, often ignored in models of sociality. To investigate relationships between social organization and growing season, I collected data on interaction rates, timing of dispersal, and body mass of woodchucks in southern Maine, and I gathered comparative data from the literature. Interaction rates peaked in spring then declined, with agonistic interactions exceeding amicable interactions in adults and in yearling males. Adult males and females weighed comparable amounts early and late in the season, but female weights lagged behind those of males in early summer. Woodchucks did not attain adult mass until after their second hibernation period. Nearly 50% of juveniles postponed dispersal beyond their first summer, and nearly half of those individuals remained philopatric in the following year. Populations faced with longer growing seasons matured more slowly, but timing of dispersal did not correspond to growing season or maturation rate. Other ecological factors, including burrow density, or benefits associated with joint hibernation, may influence timing of dispersal and degree of sociality and deserve further study.