Art. LXXI.—Red Gats and Disease.
[Read before the Wellington. Philosophical Society, 14th March, 1899.]
In 1881, at Manapouri Station, there were a good many wild cats out on the run; red ones were also common, but I heard that they were always males. I found several nests of tabby kittens during my two years there, but most of them were half-blind and sickly, so that I thought the disease would prevent them being of any great use among the rabbits. I also saw several half-grown dead ones that had apparently died of distemper. However, the reddish ones always looked big and healthy, but it took me ten years to realise that there might be some relationship between that colour and the liability to disease, which was very hard on dogs up there at that time.
I tried to rear some pups then, but they all died except two red ones that hardly got sick at all, and grew into fine
dogs. This might have given me the hint, but I did not see it until 1891, at Te Anau Downs Station, when there was a half-wild tabby cat that had a litter of kittens not far from the house. As the kittens grew, up I noticed there was one red one, and that some of the others were sick. I thought no more of them till one day the red one happened right in my path, and, as it was too weak to run away, I took it up and found it was very light, just skin and bones, but healthy-looking in the eyes, so I took it to the house and fed it, and it soon got all right, and playful Then I formed a theory—viz., that if such a starved thing as that was had taken the disease it could not have survived, and that possibly red cats were proof against distemper. This one was reared in a nest where I knew there was sickness, and I think all the rest of the family died; so that this survivor must have been proof against it, for it quickly grew into a fine cat.
I had read in “The Origin of Species” that there was some ailment in Virginia that killed white pigs while black ones were exempt; and we know that something of the same kind happens with the men in fever countries. I also remembered a pet dingo in Victoria—quite a young thing—that never took sick though tied in an infected kennel where some other pups, had died—and dingoes are about the same colour as those red cats, except the brindle markings. Perhaps it is immunity from this disease that controls the colour of the dingoes, and the immunity from the most fatal disease in a country may be the cause of uniformity of colour in the animals.
The colour of the zebras cannot be called protective, but I have heard they are proof against a poisonous fly that kills horses, though their widest difference from some ponies would be in their colours. There are no great varieties among zebras, and the variety of colour in our cattle may be due to our ignorance in killing those that may have been proof against disease. Thus we get a hint that colour may not be only protective, as naturalists hold, but may be the outward sign of internal difference that we know little about, and the idea is very like Nature's beautiful plans in everything. It is new to me in a wide sense, and I think if I had known it twenty years ago I could have made use of those red cats among the rabbits by experimenting and finding suitable mates for the red ones—perhaps tortoise-shells. Cats living wholly on rabbits are very liable to disease, and if it were not for that I think they would have been a match for the rabbits in the back country, because they catch them with the smallest expenditure of energy—by lying in wait for them—and are otherwise the most harmless animals I know.
Another instance of the relationship between colour and disease is the many white cats that are deaf.
In the Otago Witness of the 17th November, 1898, page 6, is an article on the “Wild White Cattle of Europe,” which is very suggestive from the above point of view, because it points out their great antiquity and wide distribution in the countries most liable to cattle disease; and in one sentence it says, “Why a wild race of cattle could not be of a white colour no explanation is given.” Professor Boyd Dawkins said “their white colour was fatal to the idea that they were a pure wild breed. “Thus he evidently thought that colour was only for protection, and gave no indication of constitutional differences. But those white cattle, or many of them, may have been proof against some fatal disease in that great extent of country which includes all the nations of Europe, and that may be the very reason of their wide distribution and long existence; and they may still be the fittest to survive all the diseases native to their country, even tuberculosis.
This suggests that the colour of those not taking sick in epidemics should be carefully noted and fostered, instead of adopting fancy colours in an arbitrary way, without rhyme or reason for them. There are often vagaries of colour amongst many animals, such as black sheep, black rabbits, yellow rabbits, piebald horses, &c., which we might make use of from the above point of view. The piebald horse might be the germ of the zebra's constitution if some one could only live long enough to work it up and make use of it in that country—that is, if experiments showed it to be hopeful.
In the cases of dogs and cats, where only a portion of the litters fire reared, the constitutions that may happen to vary in the proof direction will survive if left to themselves, and that may be what causes the uniformity of colour in the wild animals, while we, in picking out the ones to save, may choose the very worst ones for the sake of some whimsical colour, and that is evidently why our tame animals are of so many different) colours.
We test horses by racing and working them, and we breed from- the best; but we have no constitutional test for cows, and it is therefore no wonder that they are subject to all sorts of ailments. A system open to severe correction by some epidemic like pleuro-pneumonia will leave the proof constitutions and give us a fresh start again. I remember -when pleuro-pneumonia went through Victoria, and took about 70 per cent, of the cattle from the small farmers in the western district, and ruined many that previously thought themselves independent.
If colour does indicate constitution, even in a small way, the best individuals could often be saved and the others killed for beef, so that it would be of very great value to breeders if always kept in view. The colour of the American buffaloes,
the zebras, and many wild cattle and antelopes, could not have been for protection, and I think their uniformity proves that the colour in each case was the one that went with a constitution proof against their own epidemics.
The same might be said of the men in well-defined countries. Thus it follows that a given constitution might only be the best for its own country while fairly isolated, and that the frequent importation of foreigners may prevent the evolution of the healthiest race. For instance, the introduction of rinderpest to the South African cattle may seriously injure a fine race, as the measles injured the Fijians, and as some of our own ailments injure the Maoris. “Proof constitution” seems a clumsy term, but I noticed it used the other day by the Americans in picking out soldiers to stand the yellow fever. I do not know if they had any shade of colour to guide them, unless it might be what we call sun-browned, with the fact that they had previously escaped the sickness.