offshore islands

On three island groups off the northeast coast of New Zealand, fewer lizard species and markedly fewer individuals occurred on islands inhabited by Polynesian rats or kiore than on other islands without rats. Nocturnal, ground-dwelling lizards that forage in the open were most affected, which suggests that predation by kiore is the cause. The generally low densities and disjunct distributions of some lizards on the New Zealand mainland may have resulted from the introduction of kiore at least 600 years ago

Adele (87 ha) and Fisherman (3.6 ha) Islands lie 800 m and 1100 m, respectively, offshore in Tasman Bay, Nelson. Both are covered predominantly in native forest and scrub. There are mice (Mus musculus) on Adele Island but no rodents on Fisherman Island. Both islands are within swimming range of stoats (Mustela erminea) which have colonised Adele Island and occasionally visit Fisherman Island, 700 m distant.

Kiore (Rattus exulans) carry food to husking stations to feed, where they are sheltered from predators, competitors and rain. On four northern offshore islands of New Zealand remains of plant foods left in husking stations and in the open included seeds, leaf laminae, shoots, bark, flowers and root bases. A wide variety of animal remains were identified in husking station material, from habitats as diverse as tree tops and below the ground. All stages of both small social and large solitary insects were eaten.

New Zealand’s managed offshore islands provide sanctuary to endangered and rare fauna but also benefit common native species. These productive islands may facilitate the expansion of mobile species back to the mainland. In northern New Zealand, many mainland protected sites are located on coastal headlands within short distances of these offshore islands. Bellbirds (Anthornis melanura), locally extinct on the mainland of this region for >100 years, are capable of dispersing these distances and are occasionally sighted along the coast.