Norway rats (Rattus norvegicus)

Norway rats reward helpful companions. Credit: Manon Schweinfurth

Animal behaviour

Fair-minded rats pay helpers with food

If you give a rat a treat, it might reciprocate the favour.

‘Rub my back and I’ll give you a sweet’ — even rats engage in this kind of trade, suggesting that cooperation among animals is more widespread than previously thought.

Common rodents called Norway rats (Rattus norvegicus) are known to exchange food with each other, and to exchange grooming sessions, too. But Manon Schweinfurth and Michael Taborsky at the University of Bern wanted to know whether the animals would swap dissimilar resources, such as food in exchange for a bout of grooming.

The researchers paired test rats with partner rats that, as a result of training and experimental prompting, could provide tasty treats, grooming or nothing at all. Test animals were generally eager to groom the partners who had gifted them food, and vice versa. But test animals tended to be stingy with favours towards a partner that had given them nothing.