Food-Caching Western Scrub-Jays Keep Track of Who Was Watching When

Abstract

Western scrub-jays (Aphelocoma californica) hide food caches for future consumption, steal others' caches, and engage in tactics to minimize the chance that their own caches will be stolen. We show that scrub-jays remember which individual watched them during particular caching events and alter their recaching behavior accordingly. We found no evidence to suggest that a storer's use of cache protection tactics is cued by the observer's behavior.

Evidence for cache surveillance by a scatter-hoarding rodent

“…First, agoutis might revisit seed caches to monitor rates of seed theft. Previous studies have shown that seed-caching birds and rodents respond to an increase in cache theft rates by increasing their rate of food caching (Vander Wall & Jenkins 2003;Dally et al 2006;Huang et al 2011; but see Dally et al 2006 for alternate responses to cache theft), suggesting that this information is important to hoarders. It is possible that the agoutis in our study surveyed their caches to assess theft risk, which would allow them to recover caches and move them to safer places if necessary (Hirsch et al 2012a, b;Jansen et al 2012), but whether these activities are a response to perceived theft risk is not known.…”

“…An important factor that influences behaviour in seed-caching animals is the presence of cache thieves (Dally et al 2006). Unlike larder hoarders, scatter-hoarding animals are not able to effectively guard their cached seeds (Vander Wall & Jenkins 2003).…”

‘Theory of mind’ in animals: ways to make progress

“…If the subjects could see this competitor, they re-cached their worms in new sites once they were alone, but only if they had previous experience being pilferers themselves; conversely, if their view of the competitor was blocked, they re-cached less frequently (Emery and Clayton 2001). Furthermore, when the birds cached in one tray in front of one competitor, and in another tray in front of another competitor, they later re-cached more of the worms cached in front of the competitor that was present at that time (Dally et al 2006). Finally, if one of the two trays was less visible to the competitor-because it was behind a barrier, or further away, or in shadow-the birds not only cached more worms in this tray, they also re-cached less from it later (Dally et al , 2005.…”

“…That is, they dig up their worms and re-bury them in new locations. Furthermore, if they are given two trays to cache in, of which one is better visible to a competitor than the other, they later re-cache more from the tray that was better visible (Emery and Clayton 2001;Dally et al 2005Dally et al , 2006. A common interpretation of this behavior is that scrub jays somehow appreciate which caches are most likely to be pilfered, and then protect those specific caches by moving them to new sites .…”

“…As another example, in the 'caching paradigm', it has repeatedly been shown that when scrub jays are forced to cache in front of a competitor, they re-cache more often afterwards (Emery and Clayton 2001;Dally et al 2005Dally et al , 2006. That is, they dig up their worms and re-bury them in new locations.…”