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Volume 17, 1884
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Art. XXII.—The Plague of Rats in Nelson and Marlborough.

[Read before the Nelson Philosophical Society, 6th December, 1884.]

The plague of rats from which we at present are and have been now for some months past suffering has features which merit more than a passing notice from a Society having for one of its principal objects the discovery, corroboration, and classification of fresh facts in natural history. The magnitude of the plague is the subject of ordinary conversation. Nelson and Marlborough—in other words, the whole of the extreme northern portion of the South Island of New Zealand—is enduring a perfect invasion. Living rats are sneaking in every corner, scuttling across every path; their dead bodies in various stages of decay, and in many cases more or less mutilated, strew the roads, fields, and gardens, pollute the wells and streams, in all directions. Whatever kills the animals does not succeed in materially diminishing their numbers. Fresh battalions take the place of those slaughtered. Young and succulent crops, as of wheat and peas, are so ravaged as to be unfit for and not worth the trouble of cutting and harvesting. A young farmer the other day killed with a stout stick two hundred of the little rodents in a couple of hours in his wheat field. Plainly, the settler, for this season at all events, in addition to parroquets

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and blackbirds amongst bis small fruit, the codlin moth, American blight, scale, etc., amongst his larger fruit, the difficulty of getting in his seed and of gathering his crops through disorganization in the central weather office, and the impossibility of getting a remunerative price for what he does succeed in bringing to market, may count upon another source of comfort and profit, in addition to all those he at present possesses, in the troublesome visitor which forms the subject of this notice.

Three questions in connection with the invasion seem deserving of consideration:—1. Whence do the animals come? 2. To what species do they belong? 3. What kills them off in such numbers?

Now, as to the first question, the local journals of the past six months seem to show that the Province of Marlborough, and in particular the district about Blenheim and Picton, first had the visitation. This was, I believe, about five months ago—that is to say, in the depth of the winter. Thence the rodents made their way in a westerly direction through the Wangamoa to Wakapuaka, Nelson, and the Waimeas. Thousands of them made a mistake while passing on the eastern coast of Blind Bay towards Nelson. They took to the Boulder Bank and travelled along that curious prong of land to its very extremity. To continue their course onwards they then boldly swam across the passage leading into the harbour, rather than lose time by retracing their steps. From the Waimeas the invading force journeyed onwards round Tasman Bay to the Motueka; took possession in countless myriads of the valley of the Motueka, spread round Golden Bay, passed Collingwood, and planted their outposts even as far as Cape Farewell. They have now completely overrun the southern shores of Cook Straits, and have even appeared in great force on D'Urville Island, which apparently they could only have reached by swimming the French Pass. How far southwards the invasion has extended there seems no means of immediately ascertaining, as a great part of the country between here and the Canterbury Plains is either very sparsely peopled or unoccupied altogether. On the Lyell Road, throughout the whole distance, they are in swarms. Probably ere this, if they have continued their disposition to travel in search of fresh fields and pastures new, they have made their way to Westland and Canterbury.

Now, this is the whole of what we know as to their march: the question “whence do they come?” still virtually remains unanswered. I think, however, if we consider where they first put in their appearance, we may fairly conclude that their previous abode was somewhere in the mountainous country around the valleys of the Wairau and Awatere,—midway, perhaps, as the bird flies, between Nelson and the little township of Kaikoura. My friend Mr. Conrad Saxton, who is very well acquainted with a

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great deal of the more remote country in this district, and has moreovor great natural aptitude and appetite for observing facts in natural history, tells me that he is pretty sure that these rats are the same as he used to see in large numbers many years ago round about Tarndale,—the very district that our secretary and his party of explorers visited recently. Here, or hereabouts, are the head waters of the Clarence, Awatere, and Wairau. Of course it would be absurd for me to pretend to fix the precise spot of the original habitat; but that it was somewhere at the head of the valleys mentioned, or on the western side of Mount Odin, in the Kaikoura Range, seems to me indisputable. What other supposition can be entertained? Consider the geography of the locality in question. It is the north-eastern corner of the island with the waters of Cook Straits and the Pacific washing its coasts on the entire east and north. To these shores trend great mountain chains, like the fingers of an enormous stony hand, slightly outstretched from a big central mass more in the interior. Between these chains lie the narrow valleys mentioned above. The rats first appeared on the shores in the north-eastern corner. How did they come there? No one will contend that they swam across Cook Straits from the North Island,—or that they came from the ocean, or that they journeyed from the middle of the island where, as far as we know, they have not even as yet been seen. Unless, therefore, we assume that they dropped from the skies, or form an illustration, like Van Helmont's mice, of the doctrine of abiogenesis, we are driven to the conclusion that their original habitat was somewhere in the high, rough, and secluded country on the western side of the Kaikoura Range, whence they descended by one of the narrow valleys that I have referred to.

They probably were driven out of their old haunts by the struggle for existence (or subsistence, if you prefer the word), even as in many cases human beings are driven to emigrate; and, if we enquire what it was that pressed so severely upon the rodents, we shall probably agree that the best explanation of the movement en masse is in some exceptional climatic condition. Let it be borne in mind that last summer was very wet, and last winter very cold, the amount of snow lying on the high lands in the interior having been reported from time to time to be exceptionally large. In the month of September 5,000 sheep were at one station alone, in the Kaikoura District, Kekerangu, lost through heavy snow. Under pressure of famine, therefore, the rats, though contented enough with their habitat under ordinary circumstances, naturally braved new dangers, and made their way to the more fertile and cultivated lower country in the valleys and along the coast, where food would be found more abundantly. Another supposition would be that the struggle for existence arises from excessive increase in numbers, rather than hard winters; and a third, that the animals are attracted by

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some particular species of food which, in this particular year, and at this particular season, their instinct or their keen sense tells them would be found hereabouts in abundance. In connection with this supposition, I have heard it suggested that, as this year the birch-trees have been seeding abundantly, and thus attracting the kakas, so perhaps the rats have been drawn down from their remote homes by the same seductive food. I incline to the opinion that the recent hard winter has procured this visitation for us.

A curious fact, if it be one, here comes in. I have examined many of these animals, and have not found a single female. One of my neighbours has examined two hundred of them; and a Maori, at the pa beyond Wakapuaka, one hundred, with the same negative result. I have not heard of many female specimens as yet being taken amongst the whole host. Some females have, however, been taken; and in one case, at Wakapuaka, they were found breeding. If it really be the case that nearly all these visitors of ours are males, we may safely prognosticate that, unless there be a fusion of this race with that of the Mus decumanus or Norwegian rat, which we have with us (a thing most unlikely to occur), the infliction under which we suffer will not be of long continuance. Arguing by analogy, we should say that the young males driven, or volunteering, on a dangerous foray, will not stay long from their old quarters if they be unaccompanied by the other sex. But is it possible that the weaker males have been driven out by the stronger through jealousy,—or that, through res augustæ domi, like drones from a hive of bees, they have decamped to escape the massacre with which they were threatened by a combination of the strongest males, and the whole body of females? It will not be safe to raise a theoretical superstructure as yet upon the evidence produced. More observation is wanted, so that we may have a foundation of fact, and then we may try to answer the above questions.

Invasions of rats, from whatever cause produced, are not by any means rare in the annals of natural history. They have occurred, I am told, from time to time in different parts of this colony; and it is quite certain that both the European species—Mus rattus and Mus decumanus—appeared in Europe quite suddenly in comparatively modern times—the black rat about the year 1500, and the brown one, stupidly called the Norwegian rat, about the year 1727; both came from Central Asia, and must therefore have travelled much further than our present troublesome little visitors here in Nelson; that is, if our supposition as to the whereabouts of their original home be accepted.

But what is this rat? Is it a complete stranger or an old acquaintance? Here is a full and particular description of the adult male.

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Length of body from the tip of snout to base of tail, 4.75–5.5 inches; length of tail, 4.75–5.5 inches; length of head, about 1.6 inch; length of hind foot, about 1.25 inch; length of fore foot, about .75 inch; measurement of ears, .75 × .625 inch; whisker hairs, numerous, of various lengths, largest 1.5 inch; colour of fur (which is long, very thick, soft, and glossy), except at tips, always iron or bluish-grey, intermingled with perfectly white hairs at tips; greyish-brown on back, white on belly. The ears are rounded and naked; tail long, scaly, covered with very short hairs; legs clothed in soft hair, which in the hind feet is long and covers the claws; toes, 4 in fore-feet and 5 in hind ones, each toe provided with nails which are sharp and white at tip. Dental formula, i 1-1/1-1, m 3-3/3-3 = 16; the lower incisors large, rounded, and yellow.

Now in turning over the pages of the Transactions and Proceedings of the N.Z. Institute, I see, passim, the following species of rats noticed as found in the colony and distinguished from one another. It is not by any means easy to gather from these scattered notices the information needful for writing a clear account. Those who have examined specimens and read papers or spoken thereon at the meetings of the Philosophical Societies have differed somewhat from one another, and in some cases later information seems to have led to the withdrawal of previously expressed opinions. This seems to have arisen partly from the fact that in most cases a solitary individual specimen has been the subject. Such an one was the rat, ochreous in colour, found in 1853 (Trans., vol. iii., p. 3), and placed in the Auckland Museum. This in size was about as big as our rat, but Dr. Hector considered that it was probably a Sydney species. Again a rat of large size, with a tail 8 inches long, was found in Tinakori Road, Wellington, in 1871 (Trans., vol. iv., p. 183). It was a female, is now in the Wellington Museum, and was regarded by Professor Hutton as a specimen of Mus rattus. Two or three rats, again, were found by Mr. Taylor White near Napier, in 1876 (Trans., vol. xi., p. 343), and a skin was also found at the Port, all of which Professor Hutton regards as being specimens of Mus rattus. Then, again, in 1870 (Trans., vol. iii., p. 1), Dr. Buller communicated a paper to the Transactions, on a specimen forwarded to him from Wangaehu, which he minutely describes, and regards as the true Maori rat—the Kiore Maori. This also is deposited in the Wellington Museum. Now some of these specimens, I submit, had in all probability been stowaways on board vessels arriving at the New Zealand ports from Europe or the Australian colonies, and the accounts given of them therefore increase the difficulty of arriving at a conclusion as to what species of rats are indigenous or acclimatized in New Zealand. However, I think these three species are and have been for some time in different parts of the colony.

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The Mus decumanus—Norwegian rat—which has driven away the Kiore Maori into remote districts, if it has not exterminated it altogether.


A species of Mus rattus, of which perhaps Dr. Buller's Mus novæzealandiæ was a specimen —as indeed, he himself seems to think.


A smaller species.—for which Professor Hutton proposes the name Mus maorium (Trans., vol. ix., p. 348).

Now let us first enquire if our rat is the Mus decumanus. I think certainly not. I have had a Norwegian rat and two of our present invaders stuffed and grouped together for exhibition in our museum. A moment's inspection suffices to show what different animals these are. The fur of the Norway rat is thinner, shorter, and different in undercolour at all events. The eyes, too, are smaller. Our new friend is more like a big field-mouse than a Norway rat; and besides being considerably smaller, he is slightly darker in colour and less malodorous. He differs also in his habits, climbs trees and flax plants, is phytophagous rather than carnivorous, prefers the field to the house, the garden to the sewer; is less sagacious and crafty in preserving himself against his enemies. Some may think him a degenerate form of his Norway congener, his degeneracy produced by bush life and scanty fare. I do not think so. The argument from difference in size is too important. Besides the Mus decumanus, when it takes to the bush, attains a size which is greater than that of the animal which haunts the abodes of man. Taking to the bush, for a rodent apparently does not by any means necessarily imply starvation of individuals and general deterioration of type.

In the next place we must ask,—Is our rat the same as that described by Dr. Buller and called by him Mus novæ-zealandiæ? Comparing the descriptions of the two animals it will be seen that although their characteristic features agree pretty well in other respects, yet in the matter of size one is a comparative pigmy. If Dr. Buller's rat was the true Kiore Maori, and there was only one species of that animal, ours can scarcely be said to be the Maori rat. But when the natives told Dr. Buller that the rat from Wangaehu was the true Kiore Maori were they right? At the discussion which took place on the subject in the Wellington Philosophical Society, (Trans., vol. iii., p. 3) the question arose “whether any native now living could really identify the native rat.” And truly the point is very doubtful. I have tried by means of an interpreter to get information on the matter from amongst the Maoris who have thronged into Nelson during the last week for Land Court business. But their stories and accounts are anything but consistent with one another. They do not by any means seem to be quite clear as to there having been in olden times only one kind of rat in the country, and in all cases their information seems to be traditional,

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although some of them are aged men.** About one thing they are perfectly agreed; the Kiore Maori was good to eat; “bettern rabbit.” As to all else pertaining to the native rodent, they are about as ignorant and indifferent as the average Englishman is to the facts of natural history in his own island.

But there is a third species of rat, for which Professor Hutton proposes the name Mus maorium. (Trans., vol. xi., p. 344; vol. ix., p. 348.) Does our animal belong to this species? I think it does, and I will, with your permission, give my reasons for saying so. The Professor found in Maori cooking places at Shag Point, on Mount Benger, and I think elsewhere, at various times and under circumstances which show that they had lain where gathered for many years, certain collections of bones, principally of birds, amongst which, however, were the remains and in some cases the complete skeletons of a species of rat. He has given us exact measurements of these skeletons, and his figures and accounts are extremely interesting; for after careful consideration he entertains no doubt that this animal was the true Maori rat, and perhaps identical with the black rat of Polynesia. Now in comparing Professor Hutton's measurements of the Shag Point and Mount Benger rat skeletons, with the figures that I have given above of the dimensions of our rats, it will be found that the two sets correspond marvellously closely. The animal recently killed gives dimensions slightly larger than the desiccated skeleton, and we should naturally expect that this would be the case. My opinion is that our rats and Professor Hutton's skeletons belong to the same species, which is that of the true and probably more ancient Kiore Maori. The question then arises, what of Dr. Buller's Mus novæ-zealandiæ? What was it? Are we right in supposing that there was only one species of Kiore Maori before the settlement of the British in New Zealand in 1839–41? I do not see why we should suppose so. It is possible that there are at least two species—both varieties of the Mus rattus, both frugivorous and dwelling in trees—but one of large size inhabiting the lower country and the other smaller occupying the highlands. It is in that case to the former that Dr. Buller's specimen, the one found in Tinakori Road and several others described—would belong; and to the latter, our visitor. Perhaps one rat was a Moriori animal, the other a genuine Maori, and if that supposition cannot be accepted—perhaps the larger variety of Mus rattus came over with Captain Cook in 1769, or with some earlier navigator. In that case the small rat Mus maorium must be accepted as the original Maori animal and of the Polynesian variety of

[Footnote] * One old Maori believes that in his youth there were three rats in New Zealand—the Maori, the Norwegian, and the English—whatever he may mean by the latter.

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black rat, while the larger animal would be simply the European black rat modified to some extent by climate and other differences during the course of perhaps a hundred years.

The statement is frequently made that the Maori rat is extinct. Surely this is a gratuitous assumption. It is at all events an assertion very difficult to prove, inasmuch as it virtually involves a universal negative. That one species of the so-called Maori rat may have disappeared before the invaders, I have no difficulty in granting. But there are wide tracts in New Zealand where there is room enough for millions of rats to disport themselves without let or hindrance of pakeha or pakeha rat. Old settlers in this province who knew the interior 40 years ago, and have known it ever since, tell me that during the whole of that period a small species of rat has been commonly met with in the bush at all altitudes. One of our members (Mr. Browning) has seen it when on his professional duties at a height of 4,500 feet. Mr. Saxton says it climbs trees. Some people say it lives in them. It certainly eats fruit and vegetation, and is a very clean wholesome animal compared with the brown rat of our civilization. It lives largely amongst the fern. Why not call it by way of distinction the Fern Rat. Understand me, I do not look upon this as another variety additional to those I have mentioned, I believe this is the true Maori rat—the Mus maorium of Professor Hutton—the Kiore Maori—the rat with whose presence we now are so largely favoured.

It is fair to say, per contra, that Professor Haast in his “Report of Exploration in the Western part of the Nelson Province, 1861,” states that although the native rat (which he calls “Mus rattus”) was said in some places still to exist in large numbers, he failed to find any; while, on the other hand, the Kiore Pakeha was found everywhere in large numbers and of large size.

It must also be said that mention has been made more than once of some species of rat living in communities—like rabbits living in their burrows, or ants on their hills. The deserted holes were frequently found on the Canterbury plains and in the Nelson interior some years ago, but there is no evidence to show what species of rat inhabited them.

Well then you see the opinion to which I incline is that our rat—whether the true Kiore Maori or not—is an indigenous rodent, the same which Professor Hutton calls the Mus maorium, and which we may familiarly name the Fern Rat, in reference to its usual habitat. So far from its being extinct, this rat, as Dr. Hector says (Trans., vol. xvi., p. 555), “is very common in the bush country,” feeding on the bark of the patete, and relishing the honey of the puriri, by which it is frequently stupefied and

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poisoned. It descends into Wellington during hard weather, and if the Empire City is not spared, we must look for a like visitation from time to time.

Some say that the colour of our rat is not dark enough to admit of the opinion that it is a “Kiore Maori.” But the Mus rattus is said by a distinguished naturalist to change from black to grey—very old individuals becoming decidedly hoary (Trans., vol. iv., p. 184). We should hesitate, therefore, before pronouncing positively as to the classification of a rat from colour alone. Anatomical structure, size, and habits seem to be more important elements to consider.

3. As to what it is that causes the death of so many of our visitors— for their corpses in various stages of decomposition lie about our properties everywhere—there need be no difficulty. Their enemies are numerous. Every man's hand is against them. Dogs and cats worry them about our houses. Native birds pounce upon them in the open fields. Their more powerful congeners—the brown rats—wage war against them à outrance. A survey party in Motueka the other day dug out a rat hole, and found therein a Norwegian female and her young, and by their side about twenty skins and other remains of the smaller rat. Besides these enemies they have to contend with disease, probably occasioned by change of food and surroundings. Moreover, they do not seem to have the experience or cunning of the brown rat as to the avoidance of danger; and as their numbers are so great, their slaughter is proportionately wholesale. Between them and the brown rats there will of course be a war of races. But the black rat, neither in Europe nor here, has ever been a match for the other rodent. We shall not have these interesting strangers amongst us long—already they are diminishing in numbers, and soon they will probably retire to their mountain fastnesses as mysteriously as they descended upon us. If we did not welcome their coming, I think without doubt we shall speed the parting guests.