NATURE NOTES

New Zealand Herald, Volume LXXIII, Issue 22356, 29 February 1936, Page 1 (Supplement)

NATURE NOTES

STOATS AND WEASELS

BY B. A. FALLA

" I am sending you a specimen of one of our worst imported pests," wrote a correspondent from the Bay of Islands. The parcel duly arrived and was found to contain a stoat. She was a pretty little beast, with a long sinuous body about thirteen inches long, including a three-inch tail. The fur of the upper parts was dull mahogany brown and the tail the same, except for its black tip; the underparts were pale sulphur yellow clearly defined from the brown above. With her flat snake-like head and small ears the animal looked every inch a hunter. The stoat and its relations typify the success that has been attained by a group of small carnivorous mammals related to the larger badgers and even to the bears, and depending not on strength or staying power, but on stealth and cunning in the chase.

It is too late to bewail the importation of stoats into New Zealand as one of the major blunders of what has been called acclimatisation, except perhaps by way of repeated warning against future commissions. It may be left to etymologists to find or coin some more appropriate word than " acclimatisation " to describe this curious mania for which New Zealand has become notorious, while field biologists must busy themselves in taking stock, without bias, of the situation as it is. For if there is one thing worse than the importation of new plants and animals without full inquiry it is the attempt to control those we have, both native and introduced, without due research. This remark is not intended as a defence of stoats and weasels, but is prompted by the fact that we have no exact record of how these animals behaved when liberated, nor of their present distribution and habits.

It is well known that the original reason for importing them was the serious emergency of a plague of rabbits. Acting on the advice of " practical " men the farmers concerned imported ferrets in considerable numbers between 1882 and 1884. These animals are a domestic albino strain of the wild polecat, but are themselves not sufficiently hardy to support themselves in a wild state, nor survive hard winters. There are exceptions to this rule, but it is generally true that wild ferrets are comparatively rare in New Zealand at the present time. With the importation of the hardier stoats and weasels in thousands from 1884 onwards, a new factor was introduced into the natural balance of the fauna of the country. They both became established and the stoat, at any rate, spread rapidly.

At this stage in the chronicle it becomes nepessary to distinguish the stoat from the weasel. It is typical of the slipshod way in which we deal with our questions of wild life in New Zealand that discussion on both sides of the question so often refers to " stoats and weasels." The latter are smaller animals distinguished by white underparts and the fact that .the tail is not dark at the tip. As a rabbit control they are probably negligible, preferring rats, mice and small birds. It is even possible that they may have saved the country from a plague of small rodents, but this is ai matter on which we have absolutely no evidence; and the extent of their effect on bird life is also conjectural. Their exact distribution here is not recorded, but they are not found in many forest districts and remote parts of the country where stoats abound.

The effect of the importation on the rabbits has been considered by the late Hon. G. M. Thomson in his great work on the introduced animals and plants. The evidence considered is in the form of opinions from landholders, and although somewhat conflicting is in the main indicative that the rabbit pest began to decrease shortly after the release of stoats in the areas concerned. We now know that several factors have contributed to the final reduction of rabbits in the country to a state when they can be controlled, but it would be of value to have some information as to which of those factors are the most important. Stoats-and weasels are still legally protected in what are called Rabbit Board Districts, and in the face of possible injury to poultry, game and native birds, this should be justified by published data bearing on the stoat population of such districts and what they are actually living on.

The extent to which the spread of stoats has affected the native birds has also been recorded only in the form of opinions expressed. Allowing for the fact that stoats destroy large numbers of rats, which are themselves enemies of birds, and also that they attack many of the introduced bird species which are numerically strong and can well stand thinning, they must be accounted among the worst enemies of the flightless and ground-nesting native birds. Soon after their introduction stoats spread from the rabbit country into the wilds of south-western Otago, which was a stronghold of the kiwi, weka, kakapo and the notornis, which is now possibly extinct. With the exception of the weka these birds and many of the smaller bush birds are now rare in a region where the forest and the food supply have remained unchanged. The only possible destructive factors there have been disease, which is unlikely, rats, cats and stoats. The evidence of many observers indicates that the stoat has played a very large part in the slaughter.

North Auckland, from which district the dead stoat was sent, is a region into which the animal has penetrated in comparatively recent years. Kiwis and wekas are still more plentiful north of Whangarei than in any other part of the North Island, but they appear to be fighting a losing battle for existence. The weka is not now found, to my knowledge, in any other part of the North Island except perhaps parts of Hawke's Bay, and its range in the north is shrinking every year. About 1918 the weka disappeared from the lower Waikuto; about 1922 from the neighbourhood of Auckland; roughly four years later its southern limit was Warkworth, now it is about Maungaturoto. Residents of what is still weka country have recently petitioned the Minister of Internal Affairs to permit the destruction of wekas on the grounds that they are a menace to pheasant eggs and poultry. The parochial problem in this case is not as serious as that which stampeded South Island runholders to import the stoat and the weasel, and it is to be hoped that North Auckland residents who are the custodians of the last of the North Island wekas can be persuaded to put some extra wire netting on their poultry runs and devote attention to the many more dangerous enemies of the pheasant, if they must have pheasants.