Foraging and Predation Risk in Yellow-Bellied Marmots

Yellow-bellied marmots (Marmota fiaviventris) in the White Mountains of eastern California spent 10.2% of their foraging time on vigilance (looking up), a behavior which is necessary for predator avoidance but which reduces the rate of food intake. More time was spent looking up when alarm calls were emitted by conspecifics than in the absence of calls. Vigilance time was reduced when marmots fed in groups and in areas with many safety burrows and low vegetation. These observations suggest that the cost of antipredator behavior, expressed as a reduction in feeding rates, may be minimized by adjusting the time spent on vigilance in response to the risk of predation. Juveniles and yearlings spent more time looking up while feeding than did adults. Juveniles were also more responsive to the factors that influenced vigilance than were older animals. This may be due to the greater nutritional demands of young animals together with their higher susceptibility to predation.