Short-term social memory in the laboratory rat: its susceptibility to disturbance.

Adult rats presented with a juvenile conspecific for 5 min on two occasions, separated by a 15-min inter-exposure interval (IEI), investigated the reintroduced juvenile significantly less in the second encounter. It is suggested that this was because the adult rats remembered the identity of the juvenile, because when a novel juvenile was introduced for the second encounter, no such reduction in investigation was observed. When the rats were either handled, placed in a smaller, novel, cage, or introduced to a new juvenile midway through the IEI, investigation of the reintroduced juvenile did not decrease. This indicated that memory of that juvenile had been disrupted. However, a simple change of cage during the IEI had no disruptive effect on memory. These results suggest that routine husbandry procedures can disrupt short-term social memory, which may lead to an increase in aggression due to a failure of recognition. This has implications for the welfare of captive social animals.