Social transmission of food preferences among norway rats by marking of food sites and by gustatory contact

Three experiments were conducted to investigate the social learning and transmission of food preferences by excretory marking among adult male Norway rats. The experiments extend our earlier findings that rats prefer to eat from a food bowl marked by the excretory deposits of conspecifics and that this mechanism can result in the communication and social learning of food preferences (Laland & Plotkin, 1991). Here we investigate whether a tradition of food and food site preferences can become established by these means. Experiment 1 established that the residual cues deposited by rats lose their powers of communication as "markers" of food sites over a 72-h period. Experiment 2 showed that while a socially enhanced preference for one flavored diet could be transmitted from one animal to the next along a chain, it was unstable for an alternative diet. This suggests that social transmission may be more stable when it reinforces a prior preference than when it conflicts with one. In Experiment 3, the stability of socially transmitted food preferences was bolstered by the addition of a second process for the communication of diet preferences-namely, gustatory cues on the demonstrator's breath. This finding suggests that when a socially transmitted trait is mediated by more than one process, the processes may interact, and the diffusion is likely to be more stable.