Rodent Altruism - Lending an Anonymous Paw

Krista Zala writes a nice summary of work by Rutte and Taborsky. Some clips:

Rats given a helping paw are more prone to helping others--even complete strangers. This suggests that the animals' social life may be richer than we thought...Many animals, including rats, demonstrate direct reciprocity--described as "I'll help you if you help me." But generalized reciprocity, in which individuals remember how they were treated in the recent past and apply it to others, including strangers, has been thought to be a uniquely human trait...However, previous studies haven't specifically looked for generalized reciprocity in other animals.



To find out if rats have this capacity, Rutte and Michael Taborsky of the University of Bern in Switzerland trained rats to pull a lever that would deliver an oat flake reward to another rat on the other side of a wire mesh wall in a shared cage. Some of these rats were then put on the receiving side, paired for several days with either other rats trained to be helpful—-three different ones over the span--or with untrained rats that didn't pull the lever and provide food. After several days of living with such generous or not-so-generous neighbors, these test rats were then switched back to the lever side of the cage, paired with a new neighbor rat, and watched to see if they would provide food for it. Rats who had been paired with food-providing neighbors helped their new partner more often than those who had had unhelpful neighbors. Rutte's team also found that when a test rat was paired with one of the rats that had earlier provided it with oak flakes, it pulled the food lever even more--showing direct reciprocity. When the cage was empty of any neighbor rat, it barely pulled the food lever at all.

In a pack of 200 rats, where it's hard to remember who's been helpful and who hasn't, a general willingness to help others makes sense as a strategy...It may be a mechanism for how cooperation can evolve when you cannot recognize your partner...rats are notoriously bad at remembering other individuals.

Looking into the prevalence of generalized reciprocity among social and nonsocial animals may help our understanding of the evolution of cooperation.

The New York Times Science section has now also done a popular summary of this work (PDF here), and the graphic above is from that review.