Cache protection strategies by western scrub-jays, Aphelocoma californica: implications for social cognition

Evidence for cache surveillance by a scatter-hoarding rodent

“…To reduce the likelihood of theft, scatter hoarders have been shown to space caches out in a manner that reduces theft (Galvez et al 2009), take seeds to areas of lower seed density (Hirsch et al 2012b), make false caches in the presence of potential thieves (Steele et al 2008) and deposit caches out of view of potential robbers (Dally et al 2005a). It is possible that the cache surveillance behaviours reported here could tip-off potential cache thieves to the location of caches, thus increasing theft rates (Dally et al 2005a(Dally et al , b, 2006Steele et al 2008;Pravosudov 2008;). On one occasion, our cameras observed a cache owner usurped by another agouti while in the process of retrieving a cache (Supplementary Video S1).…”

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

“…Thus, it seems like this interpretation predicts that scrub jays should not just re-cache, but also eat, more of the caches best seen by other birds. However, this prediction seems to be met only rarely (Emery and Clayton 2001;Dally et al 2005Dally et al , 2006. Taking only statistically significant results, scrub jays re-cached more of the 'high risk' worms in thirteen out of fourteen opportunities reported, but only recovered more of them in two out of nine cases.…”

“…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 .…”

“…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.…”

“…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.…”