Multistage Scatter-Hoarding Decisions in the Gray Jay (Perisoreus canadensis)
Animals storing food in scattered sites are assumed to accrue greater fitness gains if their decisions ultimately lead to higher net rates of energy intake during cache retrieval. However, because cache survival is density dependent, maximizing the gross rate of hoarding will fail to
meet this criterion. Storing all items near a point source will yield a high hoarding rate but loss due to theft may be quite high as well. Conversely, storing all items at distant, widely scattered sites will yield a low theft rate but also a low hoarding rate. Scatter-hoarders are thus expected
to balance these conflicting forces. We investigated the behavior of gray jays (Perisoreus canadensis) exploiting experimental food sources at some distance from the forest (where all hoarding occurs). Contrary to the prediction of a rate-maximization model, the jays spaced their caches
less widely when they exploited a distant source than when they exploited a source on the edge of the forest. Redistribution of caches by the hoarders may account for this contradiction of the model, which implicitly assumes no such recaching. Jays exploiting distant ephemeral sources could
achieve a high rate of storage by temporarily concentrating their caches in trees along the edge of the forest. Later, they could reduce the vulnerability of the caches by moving some of them to widely scattered sites. A follow-up study showed that gray jays hoard in this two-stage manner
when they exploit distant sources. Rapid sequestering and subsequent recaching thus appear to be key components of a dynamic scatter-hoarding strategy.
Keywords: CACHING; DECISION MAKING; HOARDING; RATE MAXIMIZING
Document Type: Research Article
Publication date: 01 April 1997
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