“Optimal foraging”    [page 15 of handout]

Animals are often assumed to behave in ways which maximize their net rate of energy intake (Davey, 1989, p.237).. Other models of optimality are possible. In many cases species must used learning and memory in order conform to the rules of optimality models. They must also use judgements about the relative merits of various goal objects, which is different from just controlling behaviour by Thorndikean changes in the strength of motor response outputs.

Choice between better and worse prey items

It is deduced that the choice should be influenced by the availability of the most preferred item, but not by the availability of the least preferred item. (Davey, 1989; p. 241)

This has been checked with shorebirds in the field (redshank) choosing large or small worms (Goss-Custard, 1977) and pigeons choosing immediate or delayed rewards in the laboratory (Lea, 1979)

Choosing where to forage (“Patch selection”)

One theory (the “marginal value theorem”) says that an animal should leave a particular patch when its energy intake drops to the average level for the surrounding habitat. This involves the concept of an “expected rate of return”. (Davey, 1989; p245).

 

 

(see also the experiment by Harper, 1982, showing rapid judgement of amounts–graph shown on the handout | detailed text)