The Use of Foraging Areas by Yellow-Bellied Marmots

This study examines the use of foraging areas by a colony of yellow-bellied marmots (Marmota flaviventris) in the White Mountains of California. Usage indices that represent the amount of time 26 marmots fed in each of 11 foraging areas were obtained through scan-sampling of the colony's movements and correlated with habitat variables using univariate and multivariate techniques. Marmots preferred to forage in certain areas over others; of the 11 areas, five were preferred (used more often than expected based on relative size), three were less preferred and the remainder were used in proportion to their availability. Preference for foraging areas was positively correlated with food plant biomass and negatively correlated with dense, high vegetation. I interpret these results as adaptive behavior integrating the simultaneous demands of food ingestion and predator avoidance. Ageclass similarity in foraging patterns was greatest between yearlings and adults and least between juveniles and yearlings. The behavior of juveniles reflected most clearly the relationships between foraging area preferences and habitat characteristics, whereas yearlings appeared to use foraging areas largely in response to variables not measured in the study. Agespecific variations in foraging patterns may reflect the risks associated with predation and inadequate nutrition, which vary with age.