EFFECTS OF PREDATORY RISK AND RESOURCE RENEWAL ON THE TIMING OF FORAGING ACTIVITY IN A GERBIL COMMUNITY

The foraging decisions of animals are often influenced by risk of pred ation and by the renewal of resources. For example, seed-eating gerbil s on sand dunes in the Negev Desert of Israel prefer to forage in the bush microhabitat and during darker hours due to risk of predation. Al so, daily renewal of seed resource patches and timing of nightly forag ing activity in a depleting environment play important roles in specie s coexistence. We examined how these factors influence the timing of g erbil foraging by quantifying foraging activity in seed resource patch es that we experimentally renewed hourly during the night. As in previ ous work, gerbils showed strong preference for the safe bush microhabi tat and foraged less in response to high levels of illumination from n atural moon light and from artificial sources. We demonstrate here for the first time that gerbils also responded to temporal and spatial he terogeneity in predatory risk through their timing of activity over th e course of each night. Typically, gerbils concentrated their activity early in the night, but this changed with moon phase and in response to added illumination. These results can be understood in terms of the nature of patch exploitation by gerbils and the role played by the ma rginal value of energy in determining the cost of predation. They furt her show the dynamic nature of gerbil foraging decisions, with animals altering foraging efforts in response to time, microhabitat, moon pha se, illumination, and resource availability.