The social organisation and mating system of an Australian subalpine rodent, the broad-toothed rat, Mastacomys fuscus Thomas

Abstract

Mastacomys fuscus is a grass-eating rodent of south-eastern Australia that lives mainly in subalpine habitats where snow covers the ground for about four months of the year. Radiotelemetry revealed that in summer the females were territorial. Home ranges of males were larger than those of females and overlapped extensively with the home ranges of other males and with the home ranges of up to three females. In winter, males and females huddled together in communal nests. The locations of nest sites, cover, water and grass also determined the spatial organisation of individuals. The evidence suggests that M. fuscus is not monogamous, but there were insufficient data to determine whether polygyny or promiscuity is the preferred mating system. The social organisation of this species, solitary in summer and communal in winter, is a response to the cold snowy winters and the limited time for reproduction in summer. The social organisation of M, fuscus is different from that of the other conilurine rodents of Australia, but similar to that of rodents that live in other alpine regions of the world.