The MENACE of the RAT

Cue (NZERS), Issue 27, 15 July 1945, Page 24

The MENACE of the RAT

p EMEMBER the rat that got away before you entered the Army the one you discovered in the shed and prompt y chased with a pick handle, only to see it scuttle through a hole in the floorhoard and escape just when you thought you had it cornered? Beyond a momentary twinge of regret -you probably dismissed the matter from your mind. But barring accidents, such as a chance encounter with the neighbour’s terrier, a trap, poison or a more nimble pick handle than yours, the progeny of that rat -and its mate while you have been overseas .may well have totalled over 20,000,000.

- Yes, 20,000,000 rats. And that figure is based upon moderate and conservative scientific estimates. The rat family is one of Nature’s biggest mass production efforts, and many attempts have been made to calculate its reproductive potential. It is patently impossible, of course, to arrive at an estimate with any degree of accuracy, and all calculations are purely theoretical, while the additional qualification must be made that the results, in ordinary circumstances, will never be approached by Nature. But the calculations advanced by various authorities are illuminating, and, incidentally, lay further emphasis on the menace in New Zealand, where it has been found necessary to conduct rat drives in Auckland, Wellington and other •centres from time to time.

One authority, Zuschlag, assumed a pair of rats to have six litters cf eight in a year; that the young would breed when three and a-half months old; and that, with equal sexes and no deaths, the progeny at the end of the first year would be 880 rats. Another, Lantz, for the purposes of his calculations assumed the rats to breed only three times a year, and to have average litters of ten. Breeding at this rate uninterrupted for throe years, producing sexes in equal numbers, and with no deaths, the progeny of a single pair at the ninth generation would be 20,155,392 rats.

M. A. C. Hinton of the British Museum, in his book ’’Rats and Mice as Enemieis 1 of Mankind”, published in 1918, says: ’’There have been many attempts to calculate the reproductive potential of rats. For instance, F. von Fischer, in 1872, concluded that the progeny of a single pair might in ten years amount to no less than 48,319,698,843,030, 3^4,720 individuals. Rucker, more recently, has computed the increase of a pair in five years at 940,369,969,152 rats.” . ~o

The, Maoris claim to have brought the-Maori rat (kiore) with them fro® the Pacific when they migrated to New Zealand, but the ami mail is now believed to be extinct. - This species of rat was one of the four land mammals found in New Zealand when Captain Cook made his first visit, the others being a dog and two species of bats.

Of the black rat and Norway (brown) rat, familiar to present-day New Zealanders, it isieems likely that the former first invaded the country from Cook’s ’’Endeavour” while she was lying at anchor in Queen Charlotte Sound for some days in January and February, 1770. Certain it was that when Cock and Furneaux arrived at Queen Charlotte Sound three years ■later they found the rats to be extraordinarily abundant. On the other hand, the Maoris are credited with having said that rats were introduced by Tasman, but whether this is true or not it is impossible, of course, to ascertain.

The early days of New Zealand settlement found the black rat enormously abundant and moving about the country in what are described as ’’vast armies.” The settlers, bush-fellers and sawmill hands have recorded how invasions of them in countless swarms used to move through their district®, climbing everywhere and eating everything that was of a vegetable nature. It appears to be fairly certain that a good deal of the damage to orchards which has in the past been attributed to opossums has in fact been caused by the black rat.

For a long time great confusion existed in the minds cf most of thos<who observed and.- wrote of rats in New Zealand between the black, rar and the native or Maori rat. The latter was in general size about onethird that of the Norway (brown) rat' The Maoris, who prized them greatly as food and also extracted much oil from them, ma do. elaborate precautions to catch them, and hundreds would bp caught at one hunting. The animal invariably ran in a straight line and the Maoris made special lanes in order to lead them into their traps which were baited with miro and other berries ; if these lanes wore crooked, they said, the rats ran into the bush at th* bends. The native rat, which fed entirely on vegetable matter, quickly disappeared before other rats and imported cats. It was extremely rare sixty or seventy years ago, and is now. as far as is known, extinct.

Of the two principal species, the black and brown rats, the brown rat is the fiercer and more cunning- and overcomes all allied species with which it is brought in contact." Its original home would seem to have been some part of Central Asia, from where it has -spread to all parts of the world, driving cut the house-haunting species everywhere. In England it has all but exterminated the black rat, while in New Zealand it has asserted a similar dominance. The brown rat migrated westwards from Central Asia early in the eighteenth century and iis believed to have first reached Great Britain about 1730. Its already evil reputation has been increased by the fact that it is a disseminator of bubonic plague. .

The b’ack rat is distinguishable fro® the brown rat by its smaller size, longer ears and tail, and glossy black colour. It shares the roving habits of the brown rat, frequenting ships and by this means reaching all parts of the world, for which reason it is common in many places,, to which the brown

species has not yet penetrated—for instance, in South America. . This long-tailed rat, originally a native of India, would seem to have first penetrated to all part® of the world and to have nearly exterminated the indigenous rats. After this followed the. advance of the more powerful brown rat. The black rat first reached Europe in the thirteenth century.

In New Zealand the rat menace has been recognised and efforts have been made, with varied success, towards

facing up' to tire problem. Especially ils this so in the main centres, where, warehouses, factories, wharf-sheds and other large industrial buildings give domicile and sustenance to rats: Undoubtedly substantial (strides have been made in the direction of checking their progress, but the menace is one which requires constant attention, especially in a country which offers the pest ideal conditions for survival ano increase. There pre few greater threats to a nation’s well-being than the rat.