EFFECTS OF VEGETATIVE VARIATION ON WEANING SUCCESS, OVERWINTER SURVIVAL, AND SOCIAL GROUP DENSITY IN GOLDEN MARMOTS (MARMOTA-CAUDATA-AUREA)

We studied the effects of food resources on weaning success, overwinte r survival, and social group density in golden marmots (Marmota caudat a aurea), an Old World sciurid rodent. End-of-season standing crop, a measure of seasonal productivity, varied between marmot groups but see med repeatable between years. We adjusted some of our measurements of potential food availability by marmot preferences because faecal analy sis suggested that marmots foraged selectively. Some, but not all, mea sured fitness parameters were associated with variation in food availa bility. The probability of weaning young was associated with overall f ood availability the previous year, and there was a significant positi ve relationship between the early-season food resources and the propor tion of years in which a group reproduced. Weaning date, a correlate o f subsequent juvenile overwinter survival, was associated with overall food availability in the same year. Non-juvenile overwinter survival was weakly associated with food availability. Finally, marmot density was not associated with the availability of food resources. We suggest that obligate social behaviour may limit the degree to which demograp hic factors can track environmental variation.