NATURE NOTES

New Zealand Herald, Volume LXIX, Issue 21344, 19 November 1932, Page 1 (Supplement)

NATURE NOTES

TIRESOME RODENTS

BY J. DBUMMOND, F.L.S., F.Z.S.

The house rat, English rat, or black rat, with its bluish-black coat, has by no means disappeared from New Zealand. Although plentiful in and near Christchurch, its numbers in New Zealand have decreased, while the numbers of the larger brown rat, Norway rat, or common rat, have increased. These movements of rat populations have been noted in other countries, the black rat steadily giving way before the brown rat, in some cases almost suffering local extermination. The black rat's plight, and its rival's success, are more marked, perhaps, in England than anywhere else. A theory to explain the position has been put forth by an English investigator, Mr. M. A. C. Hinton, in a scheme to control destructive animals.

Both these rats were accidentally introduced into England in the same way as, later, they were introduced into New Zealand, the black rat arriving first. The black rat's original home, it is believed, was in the forests of India and of the Malay Peninsula. Probably about the time of the Norman Conquest, or of the First Crusade, it appeared in England. For hundreds of years, until the beginning of the eighteenth century, Mr. Hinton states, it was the only rat that infested English houses and shipping. It is blamed primarily for the outbreak of bubonic plague, called the Black Death, 267 years ago. It is primarily responsible for outbreaks of plague in India and in other warm countries at present.

The brown rat's original home was on the open plains of Central Asia, where the conditions are severer than in the black rat's old home. The brown rat appeared in England early in the eighteenth century. It soon spread over the whole country, using rivers and canals as its chief highways. From the sides of streams it entered drains From the drains it entered the basements of houses. From the basements it went, floor by floor, up to the garrets. For about a century it had a triumphal march. Hardy and vigorous, it almost exterminated the weak and delicate black rat. At the end of the nineteenth century the black rat was found only on vessels and on the top floors of some solidly-built granaries and breweries in some of the large ports. Small and temporary colonies of black rats were formed there occasionally. Mr. Hinton remembers the interest created at the Essex Field Club, 43" years ago, when a specimen was exhibited as an old English black rat. It proved to be a dark form of the brown rat.

His theory, simply, is that environment and breeding have favoured the brown rat. Coming from a hardy stock, inured to hardships, it does not depend on human shelter, while the black rat cannot getthrough a single English winter without seeking shelter in houses and other buildings. The theory seems reasonable as far as England is concerned, but it hardly explains the black rat's retreat before its rival in the mild climate of New Zealand. The experience in this Dominion seems to show that the more vigorous and larger species actively and directly wars on the smaller species and partly wipes it out.

Tracing the history of the browir rat in London, Mr. Hinton states that in big rebuilding operations in the present century the people built a series of palaces. They were somewhat disgusted with the brown rat. They began to realise then that a large sum was spent in* keeping the millions of brown rats which infested the city, and that it was not hygienic to have droves of them in the kitchen of every restaurant. In the new buildings a successful effort was made to have ratproof basements and ground floors. All the new buildings in one important street now are free from rats. From an old building adjoining no fewer than 5000 brown rats were taken recently in six months.

While England is shutting out the brown rat, this policy is having an unexpected result. The black rat is returning. " This poor creature," Mr.- Hinton reports, " has been clamouring to deaf ears for re-admittance to our country for a century. In the face of its rival it could do nothing without our help. At last we have done the handsome thing. We ha\ e shut out the black rat's rival; we have made attractive kitchens on the roofs and have fitted them with convenient open skylights; we have linked up roof and roof; we have bridged the horrid streets with' a network of telephone wires and cables. An arboreal species of rat hardly could imagine a nearer approach to pai'adise. There is a procession of black rats every night along the cables and over the roofs. New colonies are established in every possible place. Once more the black rat, in many parts of our great city, is the common rat. We are quickly getting back to the same state of affairs as existed in the seventeenth century."

Many years have passed since brown rats pioneered New Zealand. They annoyed Mr. A. Reischek, an early naturalist when he camped in Chalky Inlet, in the Southern Sounds. " The first night we camped on the mountains the grass country was swarming with rats. They gnawed our boots, which we kept with us in the tent. When we had supper near the fire they came behind us and nibbled the bones wo placed for the dogs. In the hut they made so much noise at night that 1 could hardly sleep. They ran over us in bed, knocked articles from the shelves and gnawed provision cases. They dug up and carried away potatoes planted in the garden. I had bird skins in a drying hut, hung on thin wires and well poisoned. Eats climbed the rafters, jumped ddwn on the skins and spoilt several."

Tho black rat may have been brought to New Zealand on Captain Cook's vessels 162 years ago. In any case, in the early days of settlement, before tho brown rat spread widely in the colony, it was very plentiful, much more so than at present. The Hon. G. M. Thomson records that it moved about the country in vast armies. Settlers, bushfellers and sawmill hands described invasions by countless swarms of black rats, which "climbed everywhere and devoured everything of a vegetable nature. Ninety-two years ago Messrs. Dodd and Davis, of Sydney, raised crops on thirty acres at Riccarton, near Christchurch. Black rats attacked the stores so vigorously that the farm was abandoned.

The Maori rat, kiore, seems to "be identical with the native rat of Polynesia. There is a belief that originally New Zealand was a ratless country, and that the Maoris brought their kiore with them at tho time of their migration from Tahiti, 500 or 600 years ago, using it for food. It is rarer than the black rat, but there is not sufficient evidence to report that it is extinct in New Zealand. Its coat is greyish-white on top, paler below. It is smaller than the brown rat, but it has a longer tail, which is the same length as its head and body, and its ears are large and round. Before Europeans came to New Zealand, Maoris caught their rats in traps and snares and roasted, steamed or potted them. The rat-catching season was opened ceremoniously, and the expert ratcatchers were subjected temporarily to strict tapu rites. For a long time the black rat, in zoological literature, was Mus rattus the brown rat was Mus decumanus and the Maori rat was Mus Maorium. Changes in zoological nomenclature give the black rat the title Rattus rattus, the brown rat is Rattus norvegicus, and the Maori rat is Rattus exulans. The mouse, which came . from the Old Country, is Mus musculua.