Summary: Bowen et al. (2012)

Individuals of a species, such as rats, may show defensive responses (hiding, fleeing, reduction in foraging) when exposed to predators or to predator-related cues. While individuals are also known to aggregate together, it is not yet known whether individuals with show these same responses in the presence of conspecifics. Bowen et al. (2012) investigated the defensive responses of rat dyads (two familiar individuals) and quads (four familiar individuals) to two stressors (bright ambient light and cat odour). They found that quads of rats responded to negative stimuli by huddling together (increased social proximity), but dyads did not show an increase in social proximity. Exposure to cat odour caused rats in both dyads and quads to decrease locomotor activity and increase defecation (signs of stress). Bowen et al. (2012) suggested that huddling is a defensive strategy for rats when they occur in larger groups, but not necessarily when they occur in pairs.