Why I Am a Christian

Monday, 31 March 2014

The Behaviour of the Koala 1. Background

     If you had visited Lone Pine Koala Sanctuary during the years, 1971 to 1973 you may have seen a strange young man sitting on a foldable cloth stool outside the main enclosure scribbling notes onto an exercise book. If the Sanctuary was quiet, he might be reading a book, his eyes flicking up to the koalas every few seconds. At other times, he might have been sitting inside one of the enclosures, or he could have been handling the koalas, or waving a camera or the microphone of a tape recorder at them.
     That strange young man was me, and I was undertaking the thesis for my Master's degree at the University of Queensland. The managers of the sanctuary, Patrick and Paul Robertson were involved in martial arts, and had a special attraction to all things Japanese. They were thus friends of my supervisor, Dr (later Prof) Jiro Kikkawa, and it was he who gained permission for me to use the Sanctuary as a centre for making the first detailed study of the behaviour of this unusual marsupial.
     Is this possible? you might ask, considering that koalas, in the wild, are solitary individuals widely scattered among the gum trees whereas, at Lone Pine they are packed like furry sardines, even sleeping on top of one another, sometimes three or four deep? Well, the answer is yes - provided you understand what you are recording, and make allowances. Obviously, such basic behaviour as walking, sleeping, eating, and so forth are not likely to be altered in captivity. As for social behaviour, it would be almost impossible to obtain enough data from wild populations, due to the fact that they are active for a few hours a day, mostly in the dark, widely separated from other individuals. However, by close examination of what goes on in captivity, it will be possible to extrapolate to the natural state. As it is, the animals of Lone Pine displayed a remarkably low level of the neuroses typical of captivity, and the sanctuary has a commendable breeding success.
     At this point, let me explain that this is a seven part article, published so as to appear in the logical order. At the end of each part, there will be links to all the other sections. In the meantime, before we examine their behaviour, let's set the scene by looking at the animals themselves.

Physical Features
     As everybody knows, koalas are soft, cute little animals with large bodies, short, chubby limbs, large heads, and an ungainly manner. They are, in fact, an animal facsimile of human babies, and anyone listening to the visitors to the Sanctuary "ooh-ing" and "aah-ing" will soon realise that this is the origin of their unique charm. Furthermore, their oft-quoted resemblance to teddy bears is also due to the fact that teddy bears, like other dolls, are also designed to resemble babies.
     My first task on undertaking the study was to draw up a table of variable characteristics, and list them against the name I gave to every individual. But pretty soon it had outlived its purpose, and I was able to distinguish every one of almost 90 individuals by sight. It was a feat which always came as a surprise to visitors, who would themselves have no difficulty distinguishing dogs of the same breed. The details have never been published before, so I might as well do it here.
     Lone Pine koalas belong to the Queensland race, and are little more than half the size of their Victorian relatives. They are sleeker, with longer faces, and less hairy ears. In the wild the fur - or rather, wool - often has a brown effusion over the shoulders and back, which soon disappears in captivity, where they are out of direct sunlight. The basic colour is grey, with the underparts being white. However, there are more than one shade of grey, and the demarcation with the underparts may be sharp or diffuse. The rump is also white, with a variable number of irregular white blotches spreading out over the lower back and the thighs. The cheeks - the area below a line drawn between the corner of the mouth and the eye - may be solid grey, or pale. The chin is always white, but it may be separated from the grey of the face with a strip of dark fur descending from the corners of the mouth. I named one young male Dracula because of this feature. Sometimes there are dark marks on the skin near the mouth. The pink circle around the eyes may be wide or narrow. The front of the nose, between the nostrils, tends to be black, and often the black extends into the nostrils themselves. On the other hand, there may be a variable amount of pink among the black. Sometimes the whole of the front of the nose is pink.
     You can understand, therefore, why it is very, very easy to tell them apart. One woman even pointed to two separate males, and asked me how I could distinguish them. I thereupon listed the whole range of features just mentioned, and ended with the comment: "In fact, you would be hard pressed to find two who were more different."
      Special mention should be made of Kalba, the albino male. He was introduced from the wild some time before I arrived and, according to all accounts, his personality was, well, wild. However, by the time I knew him, he had been handled so much, he was completely and absolutely tame. I could even hold him one hand, my arm outstretched and his rump in my cupped palm, and he would just sit there, a big, placid white ball, without even holding on to me for support.
     Not only did he lack pigmentation, but he was remarkable for a decided lack of sex drive. Nevertheless, I have been informed that, before he died, he did rally, and managed to father an offspring. By the laws of genetics, that would mean that the albino gene was now in the system, and would emerge again when his descendants interbred. But since then, more than 30 years have passed, and there have been no more white koalas.
     So far, I have said nothing about odour. The nature of our sense of smell is such that the brain filters out, and refuses to recognize, familiar background odours. Other people's houses may have a distinct smell; yours never does. Similarly, people who work with animals never notice their odour. I can honestly say that only once, for a few seconds, did the smell of the Danctuary hit me. However, visitors have told me that the place is dominated with the smell of eucalyptus, urine, and, during the breeding season, musk (presumably from the males' scent glands, of which more later).
     Nevertheless, as mentioned before, I used to sit on a foldable cloth stool, which would be left in the main enclosure upon departure. But halfway through the study, for some reason or other, I decided to take it home for a while. Now, I have no idea what effect it had on the other passengers on the two buses I had to take but, according to my mother, when I arrived home "an overpowering odour of koala" came in with me. She had to wash the fabric with Napisan to remove the smell.

Life Cycle
     The average weight of adult females is 4.45 kg (11 lb), and that of adult males 6.54 kg (16¼ lb). At the age of two both sexes are the same size, but the females stop growing the following year, whereas that of the males continues, albeit at a reduced rate, until they are at least six. By the age of 10, their teeth are showing signs of wear, and most zookeepers would consider 11 or 12 to be a normal lifespan. I believe the record was 17 years at San Diego Zoo. It is not so easy to age them in the wild, but one is known to have reached 13.
     At Lone Pine the breeding season is much earlier than in the southern populations; four-fifths of births occur between October and January. Since gestation (pregnancy) varies from 34 to 36 days, that means that mating, and all the accompaniments of mating, such as scent-marking, bellowing, and to a lesser extent, fighting, take place between September and December. It also means that the first few months of the year, when they have all settled down, and the babies are still in the pouch, are very quiet at the Sanctuary.
     The young are removed from their mothers at about 12 months of age, which appears to be consistent with what would happen in the wild. Certainly, if they are removed earlier, they get seriously distressed. What that means is that the entire breeding cycle lasts a month or two longer than a year. Thus, if a female gave birth in the first half of one breeding season, she still has time to breed in the second half of the next season. However, the following year, she will not have time to get her youngest off her hands (or rather, her back) before the season has ended. The result is that females tend to reproduce two years out of every three. Just the same, there are wild populations where the females breed every year. (There are also populations where the fertility is practically zero, due to the effects of that terrible venereal disease, chlamydia.)
      The date of birth also affects maturity. If a female is born in the first half of the breeding season, she will be ready to breed at the age of two in the second half of the season. Females born later have to wait another year. No male, however, is sexually mature until his third year, and does not reach full breeding condition for another year. Another thing: older females tend to conceive the first time they come into heat, but a two-year-old may undergo one, or even two, infertile cycles before finally conceiving.
     Now, it is time to look at their behaviour in detail.
Go to:
Part 2. Basics
Part 3. Bringing Up Baby
Part 4. Communication
Part 5. Sex
Part 6. Fighting
Part 7. Comments and References
And while we are on the subject, my friend, Robyn Tracey has written an excellent book on her experiences with brushtail possums, which you can read or download at The Possum Book.