Disruption of pairs produces pair-bond disruption in male but not female Mongolian gerbils

Previous studies have shown that separating gerbils from established male/f emale pairs has consequences for subsequent social behaviour. In males, thi s is characterized by decreased initiation of social contact, social invest igation, and either decreased aggressive behaviour or increased defense. In females, there is an increase in immobile-in-contact, which serves to term inate social encounters initiated by another animal. Although these data sh ow the effects of disrupting established pairs, they do not, per se, demons trate the existence of male/female pair-bonds. Three studies were performed to address this issue in more detail. In the first study, separating femal es from single-sex groups was found to produce similar effects to those see n following separation from male/female pairs. Generally, opposite effects were seen in males. In the second study, the effects of separating females from male/female pairs were not seen when the original cagemate was replace d with a different animal. These effects persisted in males. The third stud y revealed that the presence of a female until immediately prior to testing was crucial in producing high levels of social investigation and aggressio n in males and that the observation of decreases in these behaviours follow ing separation from male/female pairs was dependent on this. Together, thes e data show that, in males, individual housing is not a critical variable, that effects seen following the breaking of male/female pairs are not atten uated by the presence of a new female, and that these effects are not seen following separation from male/male pairs. It is concluded, therefore, that the behavioural consequences of removing males from established male/femal e pairs are due to separation from a specific female and that this is highl y indicative of the existence of a bonding mechanism in male but not female , gerbils. (C) 1998 Elsevier Science Inc.