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

Previous work comparing reproductive success of colonial and noncolonial yellow-bellied marmots (Marmota flaviventris) indicated that noncolonial 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 study and found no significant differences between colonial and noncolonial females in litter size or frequency of reproduction. We did, however, recapture a lower percentage of noncolonial offspring as yearlings; this may have resulted from early dispersal, higher mortality, or both. Further, survival of noncolonial offspring from age 1 to 2 years was lower; the cause probably was a higher dispersal rate of noncolonial versus colonial yearlings, coupled with lower survival of dispersers. We suggest that lower fitness of noncolonial females, as indicated by the apparently lower survival of their offspring and their lower likelihood of recruiting daughters to form matrilines, derives from lower quantity and quality of resources at localities of noncolonial females.