Vigilance during food handling in grey squirrels, Sciurus carolinensis

Foraging and vigilance conflict in animals that lower their head during food search and handling, but it is less clear whether these activities conflict in animals that handle food with the head raised. In these species, at least part of the foraging process is physically compatible with vigilance. Nevertheless, both vigilance and food handling require cognitive resources, so animals may not be vigilant whenever their head is raised. We tested whether grey squirrels are vigilant when they are handling food items held in their forepaws while in a semiupright posture. If vigilance occurs during handling, we predicted that squirrels finding food in a location with a partially blocked view would change location before handling to improve visibility. Because this test assumes that the benefit of vigilance during handling is greater than the cost of moving, we tested small food items (sunflower seeds) in which the temporal cost of changing position on the rate of food intake was relatively high and large items (crackers with peanut butter) in which the cost of changing position was relatively low. When handling crackers, squirrels that had their lateral view obstructed at the food presentation site changed to a position with a better view more often than controls or squirrels that had their overhead view obstructed. When handling sunflower seeds, squirrels never changed their position. These results support the view that squirrels are vigilant during semiupright handling, but that vigilance may be sacrificed if it leads to high foraging costs. (C) 2007 The Association for the Study of Animal Behaviour Published by Elsevier Ltd. All rights reserved.