Postweaning mass gain in juvenile alpine marmots Marmota marmota [Gain de masse après sevrage chez les jeunes marmotttes alpines, Marmota marmota].

Résumé

The effects of several environmental factors on the postweaning growth of wild Alpine marmots were investigated. Factors considered were years of birth, sun exposure in the home range, litter size, and sex of young. Components of growth were juvenile pass at emergence from the natal burrow (as a result of preweaning growth) and postweaning growth rate. We also considered the length of the active season during which growth occurs. Mass at emergence and postweaning growth rate varied according to year of birth, were higher in south-facing than in north-facing home ranges, and were higher in small litters. Mass at emergence was higher for males than for females. We suggest that environmental factors affected the juvenile growth pattern through influences on maternal body condition. Our results support Trombulak’s hypothesis that mothers maitian as many young as physiollogically possible. We suggest that mothers in poor condition sacrificed the mass of their offspring rather than their number. A body mass sexual dimorphism of juveniles occured at emergence, suggesting that mothers may provide more care for their male than their female offspring.