The Small Mammals of Little Nourlangie Rock, N. T IV.* Ecology of Zyzomys woodwardi, the Large Rock-rat, and Z.argurus, the Common Rock-rat, (Rodentia : Muridae)

Abstract

A capture-mark-release program was conducted on Zyzomys woodwardi and Z. argurus at Little Nourlangie Rock, N.T. From February 1977 to June 1979, 34,800 trap-nights were set for a total catch of 205 male and 148 female Z. woodwardi, and 152 male and 118 female Z. argurus. Breeding peaked in March-May, but some young were born in most other months. Rats were classed as adults on the basis of body weight (Z. woodwardi adults >70 g; Z. argurus adults >29 g). Testes became scrota1 around this weight and remained so. Significantly more males than females were caught for both species, due to the greater mobility of males, as evidenced by their high transiency rates and greater mean distances between captures. Trappability dropped to almost zero around March-April, just before the breeding season, but this was not a result of mortality or emigration. There was a clear spatial separation between species. Z. woodwardi were caught most often in the Closed Forest and no Z. argurus were resident there. The latter were most common on the Scree Slope.