The social organization and breeding system of Brants' whistling rat (Parotomys brantsii)

Brants' whistling rat Parotomys brantsii is a gregarious rodent that underg oes marked population fluctuations every few years. Previous studies have v ariously described them as solitary or social. In this field study, based o n direct observations, the social structure and breeding system of a popula tion that almost quadrupled over 7 months was investigated. At the onset of the breeding season, the animals were solitary, each occupying a separate warren. By the end of the breeding season, there was multiple occupancy of some warrens. Each individual maintained a discrete territory within the wa rren, and exhibited no apparent social behaviour. Outside the breeding seas on the behaviour of males and females did not differ and both remained at t heir resident warrens. During the breeding season male P. brantsii visited more neighbouring warrens than did the females, and their visits were to un occupied warrens or to those occupied by females. Females tended to remain within their own warren. Both sexes avoided warrens occupied by males and f ew male-male interactions were observed. Females were solicited at their wa rrens by males, who were frequently chased away. There was, however, eviden ce that reproductively receptive females were more tolerant of males, who m ay guard females following mating. This breeding system, based on competiti ve mate searching by males, and not overt aggression between males, paralle ls the scramble competition polygyny described for a number of other specie s, including North American ground squirrels.