Long-term behavioral effects of social separation during early life in a social mammal, Octodon degus

Abstract

Social separation is thought to induce a strong stress response in social juvenile mammals, but little is known about how this response might vary throughout the development. The present study examines the long-term effects of early-life stress (ELS) induced by social separation on individual behaviors later in life using the social and precocious species Octodon degus. Four experimental groups were established a positive control group of mothers and siblings from three litters comprised the socially housed (SH) group, while pups from six litters were randomly assigned to three treatments: pups experiencing no separation (NS) treatment while their siblings did; repeated bouts of consecutive separation (CS); intermittent separation (IS). We analyzed the effects of separation treatment on the frequency and duration of freezing, rearing and grooming behaviors. ELS was correlated with higher hyperactivity later in life, especially in developed males, and hyperactivity increased with more frequent separation. The SH group containing siblings that did not experience parental separation gained more weight than the other groups. The findings suggest that the NS group was indirectly affected by ELS, especially females. In summary, the long-term effects of ELS are more direct in males while those are more indirect in females.