Foraging Behaviour of Japanese Monkeys: a viewpoint of optimal foraging strategy

Most of the situations to which optimal foraging theory has been applied can be divided into the following four categories: (1) optimal food choice; (2) optimal food patch choice; (3) optimal time allocation to different food patches; (4) optimal patterns and speed of movements (Pyke et al., 1977). I have reviewed the ways in which the first three problems have been tackled thus far in primate feeding ecology. I have also reconsidered the foraging behaviour of the wild Japanese monkeys that inhabit Kinkazan Island, Miyagi Prefecture, in terms of net rate of energy intake which is usually employed as a measure in analyses of optimal foraging theory. I found that there was no significant tendency for the monkeys to spend more time in feeding on food items that are associated with more rapid energy intake. Furthermore, monkeys chose the higher-quality food patch (i. e., where the feeding speed was higher) and fed there, but showed no significant tendency to feed for a longer time in the higher-quality patch. I have discussed ecological factors other than the net rate of energy intake and social factors that influence these results. Finally, I have presented a summary of the general foraging strategies of Japanese monkeys that I have studied thus far.