RODENTIA—MICE AND GUINEA-PIGS.
The Mouse (Mus musculus).
It is probable that the mouse was introduced into New Zealand early in last century, yet the first notice of the appearance of this familiar little animal in the North Island is recorded by Dieffenbach, who wrote as late as 1839. Pastor Wohlers, long a missionary working among the Natives on Ruapuke, in Foveaux Strait, states that mice were first brought to that island in the “Elizabeth Henrietta,” which was wrecked there in 1824, and that even as late as 1873 they continued to be known as “henriettas.” The late Mr. Robert Gillies, who arrived in Otago in 1848, writing in 1872, says that it is quite certain there were no mice in Otago in 1852; but a year or perhaps two years after they were noticed, in Dunedin first. They quickly travelled south, but the Molyneux stopped their migration for a time, and it was considerably later before Molyneux Island (Inch-Clutha) was touched by them. Taylor White speaks of mice appearing in the Canterbury Plains in the early days of settlement (from 1855 onwards) “suddenly in thousands.” In 1866, during a discussion which arose at a meeting of the Canterbury Acclimatization Society as to the reported destruction of small birds by hawks, Mr. W. T. L. Travers reported “that he had opened a large number of hawks, and in all cases found their food to consist entirely of mice and grasshoppers.”
The mouse has never been found very far from the haunts of men, either in this country or elsewhere. It is abundant in all settled parts, and is also common on the Auckland, Antipodes, and Campbell Islands. Though it follows man so closely, it frequently stays in localities where men have been and have left, and there it is apt to have a bad time. Mr. Philpott, writing to me on the 2nd January, 1918, said, “There is a plague of mice in the district west of the Waiau. From Bluecliff to the Knife and Steel, near the Big River and beyond, each hut [the Government huts on the now abandoned telephone track to Puysegur Point] was overrun with them. And not only at the huts, but on the beach and in the dense bush, wherever we went, they were plentiful. At the Hump, near Lake Hauroto, they were as numerous as elsewhere. This prevalence of mice is certainly not usual; I have been on the Hump four or five times since 1911, and last year tramped along to the Knife and Steel, but, apart from an odd one or two, no mice were in evidence on former trips. One noticeable thing about these little creatures was their boldness: they were evidently very hungry. The wekas caught many of them, swallowing them whole, head first.”
How terrible a pest these rodents can be is shown by the state of affairs which has prevailed in the wheat-growing districts of Australia during the past season or two. The following note, taken from the Melbourne Age of the 17th July, 1917, gives some idea of the dimensions the pest has reached: “At Brooklyn there are nearly seven million bags of wheat, forming three and a half miles of stacks, and it is estimated that close on two million bags have yet to be railed thither from country stations. At Spotswood three million bags, most from the 1915–16 crop, are stacked.... The mouse plague in its myriads has attacked the Brooklyn stacks. The very air reeks with the smell of the mice, dead and alive. Daily to Brooklyn roll from seven hundred to eight hundred railway-trucks, loaded at the country stations mainly in the mouse-riddled areas of the Wimmera and the Mallee. From the Goulburn Valley the trucks bring with them, it is observed, mice that are few in comparison with those from the Wimmera and the Mallee. Every truck from these two regions contributes its mice to the swarming community at Brooklyn. And of the manner of the reception of these mice the instances afforded on an inspection on a week-day are at least suggestive. The average truck, when rolled alongside the wheat-stacks, is received by a handful of labourers. The bags are hauled up by tackle from truck to stack. When the last bag is lifted the doors of the truck are thrown open, and the chaff and the spoilt wheat broomed out. With the waste come flying out the mice—no great number in some trucks, but, clearly, on the average delivery of trucks a day, adding hundreds of mice to the pest, which has bitten deeply into the stacks at Brooklyn. Scattering, scampering, the mice race down the rails. A fox-terrier or two, wearing a blasé demeanour, condescend to catch a couple of mice as an example to the others. The rest of the new arrivals find shelter in the base of the wheat-stacks, or the low pile of damp, reeking bags of wheat awaiting reconditioning. Little if any effort seems to be made by the labourers to check the pest in an ordinary truck; and, indeed, a great deal of effort would be needed to be effective, and the reception and despatch of trucks must be inevitably delayed. Only when a badly infested truck, smeared with the flour of mouse-gnawn wheat, announces its contents by a vile reek of rotting mouse—an announcement beyond all risk of contradiction—it is detached, hauled off to another track, and left loaded to await special treatment.”
Two methods are adopted in Victoria to cope with the pest in the wheat-trains. One is to plug all the holes in the truck, place a sack in each corner with its mouth propped open with an iron hoop, and then proceed to lift the bags of wheat out of the truck on to the stack. The escaping mice jump into the sacks until they are nearly half-full. But if the mice are too numerous to be dealt with in this way, then they are gassed in the truck. I am not sure whether carbon disulphide or carbon dioxide is employed—probably the former. This takes at least an hour, and perhaps ten thousand mice are afterwards shovelled out of each truck; and, as hundreds of trucks full of wheat were arriving at Brooklyn each day, it is easily seen that the plague certainly was not stayed. What happens at Brooklyn has been happening in other parts of Australia, and we may be thankful that in New Zealand we have no such gigantic pests to cope with.
As the mouse breeds all the year round and produces five or six young at a birth, its rapid increase under favourable circumstances is easily understood.
The Guinea-pig (Cavia porcellus).
On the banks of the Rio de la Plata, and in the country lying to the northwards, a little animal, considered by many naturalists to be the wild form from which our domesticated guinea-pig is derived, is found in thousands. It is known as the “restless cavy.” It generally lives in moist situations, usually near the border of the forest, but never in the forest itself or in the open fields. Other authorities consider that the name “guinea-pig” is a corruption of Guiana-pig, and that the first specimens may have come from that part of America. The prevalent colours of the guinea-pig, as is well known, are white, black, and yellow, and in this respect it differs a good deal from the “restless cavy.”
It is hardly correct to include the guinea-pig among the wild animals of New Zealand, as, although it has been frequently liberated, it has never succeeded in establishing itself. At one time I had a number of guinea-pigs running wild in my garden in Maori Hill, and noticed that violets growing among the grass increased remarkably all the time they were about. The guinea-pigs kept the grass very closely nibbled, but would not touch the violets. These animals had a well-sheltered run under a thick mass of periwinkle which grew along a raised bank. They throve remarkably till a host of little ones, not much bigger than the end of one’s thumb, began to appear. This was too much for the cats in the neighbourhood. These creatures began to haunt the garden day and night. They soon ate all the little ones, and, having acquired a taste for this kind of game, they never stopped till they had destroyed all the stock but a few old bucks. There is no reason why guinea-pigs should not become wild in this country, except for the prevalence of cats.