Research On Ferrets, Stoats, And Weasels

Press, Volume CIV, Issue 30855, 14 September 1965, Page 15

Research On Ferrets, Stoats, And Weasels

Differences in the distribution of ferrets, stoats, and weasels in New Zealand can be accounted for by their food habits and the availability of food, says a progress report issued by Mr M. Fitzgerald on research being conducted by the Animal Ecology Division of the Department of Scientific and Industrial Research.

The project began in 1960 when a Fulbright research scholar, Dr. W. H. Marshall, of the University of Minnesota, was assigned to the D.S.I.R. for the purpose. On his return to the United States in 1961, the research was continued by specialist officers of the D.S.I.R.

Stoats are widespread in New Zealand in all habitats—including high-rainfall bush, alpine tussock land, arable and other farmland, swamps, and sand dunes. Ferrets are more restricted in distribution, being absent from Northland, Taranaki, Gisborne-East Coast, and Westland (although common enough in North Canterbury). These are areas where rabbits are largely absent.

Weasels are rare—and although they have been collected in Northland, Bay of Plenty, Wairoa, Taranaki, Wellington Province, Kaikoura, Canterbury, and Westland, the records are scattered. It is likely that this description of their distribution is incomplete. Food Rabbits are the most important food of ferrets, says the report, but ferrets also eat birds, and to a lesser extent frogs and fish. Stoats take a wide range of food, of which the most important items are birds, mice, rats, insects, and rabbits, the report says. “When gut contents of stoats from farmland and forest were compared, it was found that rabbits and mice were taken more often in farmland, but rats, fish, fresh-water crayfish, and insects were more often eaten in forests," says the report. “Large numbers of wetas were eaten in forest areas, but most other insects recorded were small ones, probably eaten Incidentally.” Birds are an important food for stoats in all habitats, the report says. Nest material and droppings from several stoat dens in bush areas (particularly one from Takahe Valley, in the Murchison range west of Lake Te Anau, and one from the Nelson . Lakes National Park) contained remains of both native and introduced birds, mice, and wetas. “The proportion of mice to other prey in these dens has varied, and is most probably related to changes in the number of mice,” says the report. Mice, although rarely taken by ferrets, are the most important food of weasels, which are so small that they can rarely catch rabbits, the report says. Weasels also feed

on small birds and lizards to a large extent

Stoats and weasels in the Northern Hemisphere feed mainly on mice and voles. New Zealand has very few mice in comparison with the Northern Hemisphere countries.

“In New Zealand, stoats have adapted successfully to the very different food supply, and can live largely on birds,” the report says. "Weasels, however, do not appear to have been able to modify their feeding habits, and are dependent on mice. “This may account for their rarity in New Zealand—and for the fact that they are most often taken in farmland, where mouse populations are possibly higher and more permanent than elsewhere," says the report Liberation In 1897 Ferrets, stoats, and weasels were liberated in New Zealand in 1897, according to the report, large numbers being released in both islands in areas of dense rabbit populations. However, they soon spread to the remoter parts of the country. For many years, they were protected by law as the “natural enemy” of the rabbit However, this protection was removed in 1936, by which time it had been realised that their benefit in rabbit control was outweighed by their depredations on native birds, game, and poultry.