Persistence of male/female social relationships in the Mongolian gerbil (Meriones unguiculatus)

Abstract

Undisturbed social relationships evident between pairs of male and female gerbils is little affected by the individuals' gonadal condition. In this study gerbils were caged in heterosexual pairs from the age of 3 months. All the females were ovariectomized; the males were castrated or not. More than a year later the animals were tested in paired encounters for agonistic behaviour, and then isolated. There was little agonistic behaviour between any pair 1 day after isolation. Former cagemates were re-tested 2, 4 and 8 weeks after isolation. On each occasion agonistic behaviour towards an unfamiliar animal of the opposite sex was also recorded. Although there was no increase in agonistic behaviour between cagemates until 8 weeks after isolation where the male was intact, increased aggression was evident after only 2 weeks of isolation if the male was castrated. Agonistic behaviour towards strangers was high in the first encounter, whatever the gonadal condition of the resident male, and did not increase on subsequent occasions. This suggests that the increase in aggression towards former cagemates could not be attributed to the effects of isolation itself.