Intraspecific and Seasonal Differences in the Diet of Feral Ferrets (mustela Furo) in a Pastoral Habitat, East Otago, New Zealand

New Zealand Journal of Ecology (1998) 22(2): 113-119 ©New Zealand Ecological Society Alterio and Moller, 1997) and it is commonly thought that rabbits are the main determinant of ferret distribution and abundance in New Zealand. Ferrets have been described as opportunistic predators (Smith et al., 1995) and differences between diet studies are thought to be related to the availability of prey and carrion items in the different habitats sampled. A greater understanding of the underlying dietary processes may aid in the prediction of functional and numerical responses of ferret populations to manipulations of prey, especially rabbit populations. Ferrets show a large size sexual dimorphism which is a common feature of the family Mustelidae (Moors, 1980). One hypothesis claims that sexual dimorphism is a strategy for avoiding intraspecific competition by enabling the sexes to exploit different food resources (Dayan et al., 1989). Ferret diet studies have found trends that suggest that there are dietary differences between male and female ferrets (see Smith et al., 1995). Roser and Lavers (1976) found that female ferrets ate more mice (Mus musculus L.) in winter compared to males and Pierce (1987) found that adult males ate more lagomorphs and less skinks (Oligosoma spp) and insects than adult female ferrets. However, rabbit control Introduction