Resources that animals need are usually distributed patchily within their home range, and many animals learn where they are and how to reach them. Stuart Altman describes how one troop of baboons responded to ripe berries on an isolated bush in the center of their home range as a sign of their availability elsewhere and trekked to a remote patch of bushes bearing the same fruit.

Some animals cache food when it is abundant, remember the precise locations of the caches for long periods, and return to empty the caches when food is scarce. Clark's nutcracker provides a dramatic example. The birds collect tens of thousands of pine seeds in the autumn for recovery during the subsequent winter and spring. Scrub jays caching food in the laboratory remember not only where they have cached it but also which items they have stored in which...