New Zealand Journal of Ecology (1984) 7: 139- 145

Stoats (Mustela erminea) on Adele and Fisherman Islands, Abel- Tasman-National-Park, and Other Offshore Islands in New Zealand

Research Article
R. H. Taylor  
J. A. V. Tilley  
  1. Ecology Division, DSIR, Nelson, New Zealand

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.
Fourteen stoats were trapped on Adele Island between August 1980 and February 1981. Continued trapping (12637 additional trap-nights) up to August 1983 caught only four more, but stoat tracks were still occasionally being found on the islands' sandy beaches. At their original density of about one per 9 ha stoats were readily reduced to low numbers by trapping, but on Adele Island colonisation apparently continued at the rate of one or two stoats per year.
Twenty-six New Zealand offshore islands are now known to have been colonised or visited by stoats, and many others closer than 1200 m from a stoat-infested shore are considered likely to have stoats or to be within reach of them.