A new study suggests that in the case of pilfering scrub jays, the old adage "it takes one to know one" rings true. The report, published in the current issue of Nature, reveals that birds with a history of helping themselves to others' food stores are more likely than their honest counterparts to move their cache if another bird knows its location.

Nathan J. Emery and Nicola S. Clayton of the University of Cambridge observed 21 jays in a variety of food-storing situations. The birds received a supply of worms and were given access to sand-filled caching trays both under the watchful eye of another bird and while the other bird's view was obstructed. The researchers later allowed the birds access to their stored food in private. They found that the birds re-cached significantly more items if they had been observed during their first hiding foray. What is more, birds with no experience stealing from hidden reserves belonging to other birds moved their food supply significantly less often than did thieving birds, regardless of whether they were watched. These findings, the scientists report, "suggest that jays relate information about their previous experience as a pilferer to the possibility of future stealing by another bird, and modify their caching strategy accordingly."

Additional study of cache recovery, the authors note, provides an opportunity to further examine whether mental time travel and mental attributiontraits thought to be unique to humansare in fact shared by other animals. "To our knowledge," they conclude, "this is the first experimental demonstration that a non-human animal can remember the social context of specific past events, and adjust their present behavior to avoid potentially detrimental consequences in the future, in this case pilfering."