Foraging Strategy of a Deposit Feeding Crab

Abstract

Animals living in complex natural habitats commonly exhibit simple, stereotyped behavior that is highly efficient in acquiring resources (e.g. Breck, 1978; Waage, 1979; Hanski, 1980; Ydenburg, 1984; Zimmer-Faust, 1987). Such behavior reduces central nervous system processing and simplifies decision making (Oaten, 1977; Iwasa et al., 1981; Anderson, 1983). Bookstaber and Langsam (1985) have demonstrated that stereotyped behavior can evolve under conditions of extended uncertainty, where high costs in neural investment or energetic expenditures may make it optimal for an animal not to be fully responsive to fine-grain environmental cues. Given these findings, it is important for investigators to consider the temporal and spatial scales over which foragers integrate sensory information in discriminating food resources. By sampling distributions of food on an inappropriately large scale, or by averaging measurements over time or space, investigators may conclude that one habitat yields higher payoffs than another, even though on a finer scale, there may be significant overlap in distributions of food that obscure a forager’s discrimination ability. The time and energy that a forager needs to discriminate high quality patches in complex natural habitats can become so large that the most efficient response is simply to harvest each patch encountered. Patches may then be harvested at random with respect to quality, though it might be expected that forager movements between patches will not be random in order to minimize travel and to avoid patches already visited.