![Thumbnail: [Volume 39, 1906 page 286]](/journals/rsnz/images/rsnz_39/thumbnails/rsnz_39_00_0316_0286_ac_02.gif)
The Kidney Theory.
It has always been supposed that the kea attacked the sheep for the sake of the kidneys, and the first man to dispute this, so far as I know, was Mr. F. F. C. Huddleston, of Nelson (M, N). Dr. Alfred Russell Wallace, in his book entitled “Darwinism” (G), after describing the method of the kea's attack, says, “Since then it is stated that the bird actually burrows into the living sheep, eating its way down to the kidneys, which form its special delicacy.” From the evidence of men who have seen many sheep killed and wounded by keas, this statement appears to be erroneous, and of the many correspondents that have communicated with me only one states that the bird eats the kidneys; and later on the same writer says, “I have shot many keas by the dead sheep, and they vomited up fat.” It appears as if, even in this instance, the bird eats the fat rather than kidneys.
Mr. T. Toms, of Richmond Station, Lake Tekapo, says, “I have not examined many sheep that have been killed by keas, but in the ones that I have examined I have always found the same result—the fat has been torn away and the kidneys left. Of course, the kidneys have been found mauled, but they were not sufficiently torn to give the impression that the kea had been eating them.
In three other accounts—namely, in those of Messrs. Donald Finlayson, H. E. Cameron, and C. W. Symonds—the fat was also eaten and the kidneys left exposed and untouched. Now, if the kidney itself was a special delicacy, as Dr. Wallace's book states, the keas, I think, would have eaten the kidneys as soon as they were exposed.
Mr. McKay, of Geraldine, had a kea which would not touch sheep's kidneys. He says, “I repeatedly tried him [the kea] with kidney - fat and the kidneys themselves, but he would scarcely deign to put his beak into them.”
One reason why people suppose the kea to be fond of kidneys is that the keas nearly always attack the sheep on the loin just near these organs, and, as they eat their way through the flesh and fat, people have jumped to the conclusion that they must be after the kidneys.
![Thumbnail: [Volume 39, 1906 page 287]](/journals/rsnz/images/rsnz_39/thumbnails/rsnz_39_00_0317_0287_ac_02.gif)
In looking through the authentic accounts of about fifty eye-witnesses, I cannot find any evidence to support the kidney theory. The reason for the keas always tearing open the sheep above the kidneys can be explained, I think, by the way the bird attacks sheep. All my correspondents with three exceptions say that, from what they have seen, the kea always settles on the rump. Mr. R. Guthrie thinks that they only settle on the shoulders when the sheep is stuck in the snow, but I have an instance where the shoulders were eaten and the sheep was not caught in the snow.
The reasons for the keas always settling on the hind quarters are as follows: Firstly, the rump of the sheep is its widest part, and so it makes a firm platform for the kea to settle on and to get a firm hold. Several witnesses say that it is almost impossible for the kea to keep on a sheep's back unless he perches on this part. Mr. Guthrie says, “It is almost impossible for a kea to stick on a sheep's back while pecking it in any other position than behind the kidneys, facing the head. I have seen them trying to hang on to a sheep's back, but unless they were in the position described they could not stick on for ten yards.” Secondly, when flying after a sheep, the rump is the nearest and handiest part to settle on, and as the birds often have to alight on the sheep while it is running, it is no wonder that the rump is that part chosen. Though keas seem fond of mutton-fat, I do not consider that this is the only reason why they make for the loin. It naturally follows that when perched on the sheep's hind quarters the bird will commence to pick the sheep's back at the handiest part: this, without doubt, will be the part that is under the kea's nose—namely, the loin. Again, the loin is very easy to tear open, owing to the absence of ribs, and this again would commend itself to the bird.
To me it seems that the preceding reasons do more to influence the kea when attacking than the presence of the kidney-fat. Even the first-recorded accounts of sheep-killing mention that the bird attacked the loin, and the only way to explain this is that the kea found the loin the easiest and handiest part to attack. I can hardly believe, as some people do, that by some kind of instinct the kea knew where the kidney-fat was to be found in the live sheep. This latter idea is somewhat upset by the fact that cases have been seen where the flesh around the backbone has been eaten, and the kidney and the kidney-fat left almost untouched.
The kea appears to eat whatever part of the sheep comes first—first the skin and flesh, then on to the kidney-fat. In some cases they do not even eat all the kidney-fat, but begin
![Thumbnail: [Volume 39, 1906 page 288]](/journals/rsnz/images/rsnz_39/thumbnails/rsnz_39_00_0318_0288_ac_02.gif)
to pull out the intestine, and several sheep have been found alive with these organs protruding. Mr. A. Wilson says, “One day I came suddenly upon two or three keas, busy picking at the loin of what I supposed to be a dead sheep. There was a hole right through the sheep's back, and the birds were putting their heads right through to the inside of the sheep and pulling out portions of the intestine, but I cannot say if they are them or not. I then went over, and to my surprise I found that the sheep was not dead, so I killed it to put it out of pain.”
It is evident that these birds do not mind what part they attack as long as they get something to eat, and when a sheep is buried in the snow they go for the handiest part. Mr. E. Cameron says, “A snow-slip carried some sheep with it. I found the sheep stuck in the snow, where it landed, still alive, with its hind leg eaten to the bone, and half a dozen keas tearing away at him.”
I think that the theory about the bird killing the sheep for the kidney alone is entirely wrong, and I doubt very much if the kidneys are in any way the source of attraction. The birds certainly do not leave the sheep to die a lingering death while their hunger is unappeased, unless they are disturbed.
As to the kidney-fat theory, though this has some evidence to support it, I think that it is mostly because these parts are easiest to get at. The very fact that the keas eat all parts of a carcase except the wool and bones rather weakens this theory.