The Kea: a New Zealand problem/Chapter 8
CHAPTER VIII.
GETTING INTO BAD HABITS.
I must be free as the wildest thing
. . . . . . . . . . . . . . . .
Free on the blast to be borne away.”
—William Pember Reeves.
I am almost certain that too much emphasis has been laid on the fact that the Kea, a member of the brush-tongued parrot family, has changed its ordinary diet and taken to eating meat and fat. When we consider the natural diet of the bird, the change seems more or less natural, for there seems to be very little difference between eating a large plump grub and a piece of fat.
The more interesting fact is that, in addition to this, it has changed its character, and, from being a harmless parrot, has become a bird of prey of no mean order.
Other birds, in confinement at all events, have been known to eat meat, though in nature they seem to content themselves with fruit and seeds. For example, many parrots and cockatoos seem thoroughly to enjoy cleaning up bones with particles of flesh on them. Again, in New Zealand, the little white-eye (Zosterops caerulescens), whose natural food is blight, small insects and fruit, can be easily trapped, in winter especially, by means of suet fat or meat bones, both of which it devours readily.
Therefore it seems to me that there is nothing very wonderful in the fact that the Kea enjoys a little meat and fat in addition to its ordinary food.
Another interesting case is that reported by Captain Hende, of British East Africa, and forwarded to “Nature” by Professor E. Ray Lankester, on 10th August, 1900. It runs as follows:—“The common rhinoceros bird (Buphaga erythrorhyncha) here formerly fed on ticks and other parasites which infest game and domestic animals; occasionally, if an animal had a sore, the bird would probe the sore to such an extent that sometimes it killed the animal. Since the cattle plague destroyed the immense herds in Ukamihani, and nearly all the sheep and goats were eaten during the late famine, the birds, deprived of their food, have become carnivorous, and now any domestic animal, not constantly watched, is killed by them. Perfectly healthy animals have their ears eaten down to the bone, holes torn in their backs and in the femoral region.”
It will thus be seen that at least three kinds of insectivorous and fruit-eating birds are known to eat fat and meat on special occasions.
When we look at the circumstances that forced the Kea to add to its diet, it would have been more wonderful if the bird had refused to touch the new food.
Unfortunately for science, as the Kea had learned to kill sheep before men were aware of it, we shall never be able now to decide finally what set of circumstances caused him to change; but I think that the truth is confined to the last two of the following three theories.
Whether the change of diet was influenced in the way explained by either one or both of those theories it is hard to say; but so far no other reason can be given to which it is worth while giving serious consideration.
THE VEGETABLE SHEEP THEORY.
This was the earliest and for many years the most popular; but, when further investigation brought to light many new facts, the theory lost favour, though even to-day some people adhere to it.
The vegetable sheep, after which I have named the theory, is one of the most interesting of our alpine plants. Owing to its cushiony appearance it is often erroneously termed a moss or fungus. The name includes two closely allied plants, which grow especially on the mountainous country of the northern half of the South Island, at an altitude of from 4,000 feet to 6,000 feet above sea-level.
Dr. L. Cockayne makes the following comment upon them: “The rocks of the alpine summits weathering away, and the rain not being sufficient to bear all the debris down into the valleys, an enormous quantity of angular stones collects on the mountain sides in many places, which may form steep slopes for thousands of feet. As the climber wearily ascends
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The vegetable sheep (Baoulia eximia), Mt. Torlesse, Canterbury.
these shingle slips, as they are called, progress is slow; the tones continually slip beneath his feet, and slide down the slope. No place could seem more unlikely to support vegetable life. It is in truth a veritable alpine desert. . . . . On these shingle slips the wonderful vegetable sheep are encountered. These grow, not on the shingle, but on the rocks which the stones have nearly buried. Large examples form great hummocks six feet long by three feet across, or even more. Really they are shrubs of the daisy family, and are provided with a thick, stout, woody main stem and strong roots, which pass far into the rock crevices. Above, the stems branch again and again, and towards their extremities are covered with small woolly leaves, packed as tightly as possible. Finally stems, branches and leaves are all pressed into a dense, hard, convex mass, making an excellent seat for a wearied botanist. Within the plant is a peat made of its rotting leaves and branches, which holds water like a sponge, and into which the final branchlets put their roots: thus the plant lives in a great measure on its own decay.”
There are two kinds; a finer one (Raoulia eximia) which is of a greyish blue colour, and is found over many mountains in Canterbury, and a coarser kind (Haastia pulvinaris) which is of a yellowish brown colour and is confined to the mountains just north of Canterbury.
At a distance a number of these plants do somewhat resemble a few sheep lying down; hence the name.
The supporters of the theory hold that the Kea was in the habit of tearing open these plants in order to get out the large white grubs, which were said to live in them; and that, when sheep first wandered into the birds’ domain, they were mistaken for the woolly vegetable sheep. The bird, with the intention of digging out the grubs, was supposed to tear open the animal’s skin, and, finding meat and fat even more appetising than the grubs, persisted in its efforts and so acquired the habit of sheep-killing.
All this sounds very reasonable, but unfortunately for the theorists it will not bear investigation.
The first objection is that, where the Kea was first known to attack sheep, the true vegetable sheep are unknown, and many mosses are just as conspicuous as the species of Raoulia that grows around Lake Wanaka. Raoulia eximia does not grow further south than Mt. Ida in Central Otago, at present its only known habitat in that province.
Secondly, no large white grubs, big enough to cause the Kea to tear up these tough plants, have ever (as far as I can ascertain) been found in such numbers as to attract the birds; and, though I have often torn the plants to pieces, I have never found any large insect larvae.
Thirdly, if the Kea feeds on the grubs that are said to live in these plants, one would expect to find the shrubs partly torn up; but I can find no evidence in favour of this. Though I have been upon the ranges where both Keas and vegetable sheep were numerous, I have always found the plants intact.
Lastly, when the Kea first attacked sheep, according to the first accounts, the shoulder or the rump, the latter in preference, was the part chosen. Now, if the bird were in the first instance looking for grubs, he would almost be certain to have worked right along the back: but the evidence disproves this.
It therefore seems to me that, unless some very strong new evidence is forthcoming in support of this theory, we have no alternative but to leave it in future out of consideration.
THE CURIOSITY THEORY.
The supporters of this theory say that it has been nothing but the Kea’s insatiable curiosity and love of investigation that has got it into the habit of sheep-killing.
As has been shown in a previous chapter, it is never happier than when it is pulling something to pieces, and anything with a strange appearance is always a temptation too strong for the Kea to resist. Now, the suggestion embodied in the theory is this—that, when sheep first wandered into the Kea’s domain, as the bird had very likely never before in its life seen anything that walked on four legs, this woolly animal at once aroused its curiosity. With the Kea, to wish to investigate is to do it, and the sheep became a centre of attraction.
The bird would no doubt walk round these strange animals and inspect them from all sides, and when satisfied with the view from the ground it would fly on to the sheep’s back.
This would naturally cause the sheep to move, and the Kea would soon tumble off, no doubt thoroughly enjoying the novelty.
In this way, by repeated failures, the bird would soon acquire the knack of holding on to a sheep while it was running.
Once on the back of a sheep, the bird would now want some other novelty to amuse itself with, and the woolly fleece would become the next object of investigation.
Soon the flesh and fat would be reached; and, the bird finding these new morsels much to its taste, the art of sheep-killing would soon be acquired.
In this country the heavy snow storms often bury or practically bury many sheep. The struggles of a half-buried beast would soon attract the Kea; and, finding the animal an easy prey, it would soon begin its depredations.
This theory has something in its favour, and no doubt does to some extent account for the bird’s change of character.
THE HUNGER THEORY.
This one appears to me to explain to a larger extent the cause of the Kea’s downfall, and as food is a necessity the fall was somewhat natural.
There is a good deal of evidence to show that lack of ordinary food greatly influenced the Kea towards sheep-killing.
As the Kea feeds on berries, grubs, roots, etc., there is no doubt that in winter and spring the excessive snow and heavy frost, so prevalent in Kea country, must often make the procuring of food very difficult. Again, as at this period the eggs are sometimes laid, and perhaps the young ones have to be fed, the lack of ordinary food must at times make the bird desperate.
If this did not in the first instance cause the parrot to kill sheep, it seems now to affect the number killed, for usually a severe winter, accompanied by heavy snow-falls, means a heavy death toll levied on the flocks by Keas.
The pastoral homesteads are scattered in the valleys of the foot-hills. The Kea, wandering about in quest of something to satisfy its intense hunger, would, on reaching the lower levels, come across the meat gallows, where very likely the carcase of a sheep would hang, or at least some skins with pieces of meat and fat still adhering to them would be thrown over the fence to dry.
In trying everything with its powerful beak to see if it were edible, it would soon taste the pieces on the skins or
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The meat gallows on which Sheep for home consumption are hung after they have been killed.
even from the carcase itself; and, finding them much to his taste and easily procurable, it would soon acquire a liking for them.
If the skins and carcase were absent, there would always be a number of sheep's heads scattered around the gallows, and the Keas could there always find something to eat.
It is said that, in the early days, miners prospecting for gold often killed a sheep for food, and, roughly skinning it, would leave the skin and much offal on the ground, thus giving the Kea ample opportunity to get the taste for meat.
Once having acquired the carnivorous taste, it would soon find out that the dead sheep lying about the station contained the same kind of food, and that by tearing off the wool a good meal was always to be had. Tearing at the half-dead sheep, buried in the snow, would be its next step on the downward course; and, finding a lack of dead sheep it would soon begin to attempt to eat the animal while it was running about. The wounds thus caused would soon mortify and cause the animal’s death, and so the Kea would find an ever accessible method of acquiring a meal.
Some early writers suggest that, as the bird formerly fed on insect larvae, the finding of a dead sheep in an advanced stage of decomposition gave them the taste for meat. In this way, the carcases being often full of maggots from the eggs of the ever-present blow-fly, as the Kea picked out the maggots it would at the same time eat pieces of meat and so acquire the taste for flesh.
This may in some measure have influenced the bird; at any rate, it would largely account for some Keas being fond of bad meat.
The following information, forwarded by Mr. James McDonald, adds weight to the hunger theory, especially as the killing first began on the station of which he speaks.
In a letter to me he says:—“I would like to say one thing in answer to the question why the Wanaka Station suffered first by the Kea. My opinion is that it was because this station was the first to send men out to the out-huts in winter where they had to kill their own mutton. The skin was hung up on a fence or a bush, and the birds, driven to lower levels by the heavy snow which covered everything, came down in numbers to pick at the skins and entrails. When deprived of this they began to kill sheep for themselves, after having acquired the taste from the food obtained at the huts.”
What particular group of facts covered by the Hunger Theory really caused the Kea to change I do not know; but I think that this theory indicates in what direction the true cause may be found.