‘Rub my back and I’ll give you a sweet’ — rats engage in this kind of trade, suggesting that cooperation among animals is more widespread than thought.
Norway rats are known to exchange food and grooming sessions. But investigators wanted to know whether the animals would swap dissimilar resources, such as food in exchange for grooming.
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 favors towards a partner that had given them nothing.