Foraging currencies and the load-size decision of scatter-hoarding grey jays

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Food-hoarding animals are assumed to maximize total storage while meeting their own energetic requirements. To maintain energetic balance, a hoarder must also devote some time to feeding. The predicted choice of hoarding strategy depends on the net rate at which a hoarder is able to feed itself. Rate-maximizing hoarding is favoured when the net self-feeding rate is high, as it was during our experiment. (At lower net self-feeding rates, the hoarder should behave more efficiently.) To evaluate the expectation of rate maximization, we examined load-size decisions (number of raisins collected for storage) made by hoarding grey jays, Perisoreus canadensis. During each visit to an experimental food source, the subject was forced to wait for access to the food. Following this delay, the jay collected a load, transported it for storage, and returned to the source. The predicted size of rate- and efficiency-maximizing loads diverged with increases in the delay. As predicted by both currencies, the jays collected larger loads following longer delays. The magnitude of the observed adjustments indicates that the jays closely approached the maximal rate of hoarding. © 1996 The Association for the Study of Animal Behaviour.

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Animal Behaviour