Eurasian Jays are known for caching food and remembering its location for later. They're also known for their tendency to pilfer the caches of other jays. To protect their caches against potential thieves, jays take efforts to conceal both visual and auditory information about their cache location. For instance, individuals will cache at a distance from other jays or cache behind barriers. If jays have been observed during caching, they often recover and move items to new locations once the potential thief is no longer in view. And in terms of concealing auditory information, jays prefer to bury their food in quieter substrates (like sand, rather than noisier gravel) when another bird can hear but cannot see them.
In a new study, Rachael Shaw, of Victoria University of Wellington, and Nicola Clayton, of the University of Cambridge, tested whether Eurasian jays can recall and use both visual and auditory information when stealing other birds' caches. Shaw and Clayton tested the jays when they had no information about the location of another bird's cache, after the jays had observed and heard another bird caching, and after the jays had heard but not seen the caching. The birds cached in two substrates: noisy gravel and silent sand.
When jays had neither visual nor acoustic information about caching, their pilfering performance was poor; essentially, they searched at random. When jays were able to see and hear another bird caching in the noisy gravel or quiet sand, they located more caches, focused their searches on the correct substrate type, and searched in fewer empty locations to find the first cache. Jays who listened to caching in gravel and sand, but were unable to see the caching, also found more caches and searched in the correct substrate more often.
"Our study suggests that jays possess observational spatial memory — when a jay had seen another bird caching, they were subsequently able to find the caches more accurately and more frequently than if they had relied on a random search strategy," says Shaw.
The results also raise the possibility that jays can recall and use auditory cues to locate caches, even in the absence of any visual information. Listening to another bird caching in either gravel or sand may have helped pilfering jays identify the substrate in which the caches were made.
Shaw says that in the Eurasian jays' forest habitat, it can be hard to see everything that's going on through the trees. "To be an effective thief, it may well pay for the jays to use auditory cues to figure out that another individual is caching nearby," she says.
By eavesdropping on the sound of other birds caching, jays can figure out where to search for their next stolen meal.
Reference:
Shaw, R. C. and Clayton, N. S. (2014). Pilfering Eurasian jays use visual and acoustic information to locate caches. Animal Cognition. doi: 10.1017/s10071-014-0763-y.
