TIME-DEPENDENT AVERAGING OF FORAGING INFORMATION IN LEAST CHIPMUNKS AND GOLDEN-MANTLED GROUND-SQUIRRELS

Behavioural adaptations to resource variability were examined in field experiments with least chipmunks, Tamias minimus' and golden-mantled ground squirrels, Spermophilus lateralis. Artificial patches of unhullcd sunflower seeds were held stable or varied in quality. The rate at which the unstable patches changed and the length of time elapsing before animals could choose between them were systematically varied. When their foraging information grew older and lost its reliability, the animals depended less on recent experience and more on patch averages in making their choices. The rate at which the transition occurred was related to the rate of patch change. These adaptations were predicted by a dynamic patch assessment model that weights patch information according to its reliability. © 1993 The Association for the Study of Animal Behaviour.