Animal distribution is strongly controlled by climate, especially at higher altitudes where harsher conditions favour fewer vertebrate species. A predicted consequence of climate change is increased pressure on these higher-altitude faunal communities by invasion of lower-altitude species more suited to warmer conditions. The distribution of two such species, the broad-toothed rat (Mastacomys fuscus) and swamp rat (Rattus lutreolus) (with the former generally occurring at higher altitude except in Tasmania), were examined using BIOCLIM. Modelled climate change with a 20% reduction in precipitation and a warming of 2.9°C at latitude 36°S (Snowy Mountains) and 3.4°C at 42°S (central Tasmania) suggests that M. fuscus will retreat to higher altitudes. The core areas of R. lutreolus will also contract, but significantly they will also move so that they overlap current core areas of M. fuscus on the mainland. Barrington Tops is the northernmost known location for M. fuscus and is climatically marginal. The recent invasion of Barrington Tops by R. lutreolus and decline of M. fuscus raises the question as to whether the modelled broader range changes will result in greater competition between the invading R. lutreolus and the cool-climate specialist M. fuscus, resulting in the further loss of the latter.