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SOME OBSERVATIONS ON THE ECOLOGY OF RODENTS IN ORONGORONGO VALLEY (NEW ZEALAND)

New Zealand seems to be an ideal ecological laboratory for studying small mammals. There are relatively few mammalian species, most of them being introduced. These include four species of rodents—the "native" Rattus exulans (introduced by the Maori perhaps 100 years ago) and Mus musculus, Rattus rattus and Rattus norvegicus, introduced in the 19th century. In Orongorongo, where this study was made, only M. musculus and Rattus rattus occur. The small number of species and the wide variety of ecological niches available have an important impact on the ecology of the rodents resulting in a much wider distribution than in their native environments. In Europe both species are generally restricted to human habitats and their surroundings. In New Zealand they are distributed in almost all available biotopes and Rattus rattus is largely arboreal (Watson, 1959; Daniel, 1972). There is quite abundant literature on the ecology and general distribution of jR. rattus in New Zealand (Best, 1968 ; Beweridge and Daniel, 1965; Daniel, 1972; Daniel, 1972; Daniel and Karl, 1973 ; Watson, 1953 ; Watson, 1959 ; Wodzicki, 1950) but very little on M. musculus. This research was carried out, during my study leave from the University of Zambia, Lusaka, at the DSIR Ecology Division Field Station in Orongorongo Valley.