Social Organisation in the Rufous Bettong, Aepyprymnus Rufescens

Abstract

This study examined association patterns and reproductive behaviour in a sexually monomorphic potoroid marsupial, the rufous bettong, Aepyprymnus rufescens. A total of 29 individuals was marked, and 22 of these were observed regularly over a six-month period; these 22 individuals accounted for almost all the animals using the study area. Rufous bettongs at this site were predominantly solitary (71% of sightings were of single animals) and groups, when they formed, were generally small (maximum of six individuals). Most groups of two were male-female pairs, and unisex groups occurred significantly less often than expected. These male-female groups formed as a result of sexual investigations of females by males, and were shore-lived. Analysis of the frequency with which particular males and females were seen together (excluding occasions when females were in oestrus) showed that most males did not persistently associate with any particular female. Instead, they appeared to maintain transitory contact with as many females as possible. However, three pairs were regularly seen together, suggesting that some males may maintain especially close contact with particular females. Females as they approached oestrus were followed continually by several males, with one male following very closely and preventing others from approaching. In two well-studied cases, the male who defended priority of access to the female was the same individual who had most often associated with that female when not in oestrus. These males demonstrated intimate knowledge of the nesting locations of the females and were able to join them very early each evening, and defended them against other males with little overt aggression. The mating system in this population appears to be promiscuous, but with a hint of monogamy arising from the tendency of some males to persistently investigate and ultimately to guard sexual access to certain individual females.