The density of indigenous invertebrates on three islands in Breaksea Sound, Fiordland, in relation to the distribution of introduced mammals

Abstract

The density of indigenous invertebrates was sampled on three islands in Fiordland which have similar soils, vegetation and climate, and presumably also originally had similar invertebrate faunas. Resolution Island (20,860 ha) now supports stoats and deer, and Breaksea Island (150 ha) has Norway rats; Gilbert Island No.6 (20 ha) is still completely free of mammals. Compared with Gilbert No. 6, the densities of 13 groups of invertebrates were lower on Breaksea, and the densities of 2 groups were lower on Resolution. We interpret these differences to be the result of disturbance and predation by mammals introduced within the last 200 years.

Keywords:

• Rattus norvegicus
• Mustela erminea
• predation
• Fiordland
• invertebrates
• islands