Handling and isolation in three strains of rats affect open field, exploration, hoarding and predation

Male albino (Al), brown hooded (Br) and black hooded (Bl) rats were raised in social isolation or in pairs, with or without systematic handling. At 90 and 180 days of age, the animals were individually tested for activity in an open field (Of), exploratory behavior in a complex environment, food hoarding (Hd) and insect predation (Pd). Multivariate analysis of the results showed significant influences of all three factors (strain, handling and social isolation) and interactions among them. Strain affected Of, Hd and Pd, with contrastingly high performances of Br in Of, Al in Hd and Bl in Pd. Handling increased Of and exploration scores in both test series. Isolation induced higher performances in all the four behaviors in the second test series. Accentuated and stable individual differences occurred in the performances off all the behaviors. The results emphasize the subtleness and complexity of the interplay of genetic and environmental influences and stress the independence of the regulatory processes of different behaviors.