REPRODUCTIVE SUCCESS OF COLONIAL AND NONCOLONIAL FEMALE YELLOW-BELLIED MARMOTS (MARMOTA-FLAVIVENTRIS)

Previous work comparing reproductive success of colonial and noncoloni al yellow-bellied marmots (Marmota flaviventris) indicated that noncol onial females had lower fitness; they reproduced less often and their offspring had a lower survival to age 1 year. This work, however, may have been affected by a bias in sampling effort. We initiated a new st udy and found no significant differences between colonial and noncolon ial females in litter size or frequency of reproduction. We did, howev er, recapture a lower percentage of noncolonial offspring as yearlings ; this may have resulted from early dispersal, higher mortality, or bo th. Further, survival of noncolonial offspring from age 1 to 2 years w as lower; the cause probably was a higher dispersal rate of noncolonia l versus colonial yearlings, coupled with lower survival of dispersers . We suggest that lower fitness of noncolonial females, as indicated b y the apparently lower survival of their offspring and their lower lik elihood of recruiting daughters to form matrilines, derives from lower quantity and quality of resources at localities of noncolonial female s.