Why I Am a Christian

Monday, 31 March 2014

The Behaviour of the Koala. 2. Basics

     The first thing a visitor to the Sanctuary will notice is that most of the koalas are curled up asleep in a fork of a tree. Sleeping is their major "activity", followed by eating. Typically, the head is down and the arms folded, or clasping the tree, but the whole of their weight rests on a small section of the rump where the skin lies right next to the bone. The photo at left demonstrates it perfectly. (Yes, I know it's not 100% in focus, but please understand that this was the first time I had ever used a single lens reflex camera.) On hot days they will sprawl out in all sorts of odd positions, always taking the weight on the same spot. Cubs curl up in much the same way in their mother's laps, and adults may even sit like that on the ground, or sit like a dog, or sometimes squat like a man. When it is really hot, some of them spread out on their bellies.
     My first task on arrival every morning was to record where each individual was sleeping. Far more often than would be predicted by chance, they would be found asleep in one favourite tree or the two immediately adjacent, nor did these preferences change over a period of years. Visitors who see one individual sleeping on top of another normally assume they are related. Not so. In captivity, where the koalas are completely habituated to the presence of others, they merely regard the back of a companion as a softer kind of branch and, although newly weaned cubs prefer to sleep in contact with an adult, adults were seen sleeping like that only 8% of the time, which was only a quarter of what would be expected by chance. Just the same, it is amazing what they will put up with. I have actually seen a koala sleeping quite happily under a pile of six or seven others.
     Of course, the daily cycle of activity at Lone Pine is a bit artificial, because fresh leaves are brought in during the afternoon. So what happens at night? I gained permission to spend two nights there, one during the first half of the night, and another during the second half. And thereby hangs a tale - or rather, two. It was incredibly boring sitting there in the dark with nothing to do but listen to the noisy chomp-chomp-chomp of feeding koalas, or flash a torch over them, and see nothing but animals eating or sleeping. Also, no matter how much sleep I had had during the day, it was very, very tiring. At one point I lay down on a bench for a short nap. It was completely dark. How was I to see the notice saying, "Wet Paint"?
     [I cannot tell a lie by omission, not even for the sake of a good story. Although the paint was a bit sticky, it was already sufficiently dry not to come off on my clothes.]
     Then there was the high drama that ended the first night's vigil. To understand it, you must appreciate the set up at the Sanctuary at the time. The Sanctuary headquarters was outside the enclosure. There was a café there run by two old ladies, who lived in a cottage next to the café/HQ. This HQ was connected to the main pen inside the enclosure by a telephone. Remember, this was long before the onset of mobile phones. On the night in question, I was told that, when I wanted to end my vigil, I should use that phone to call a taxi. Well, about the middle of the night, that's what I tried to do - but every time I dialed the number, all that happened was that the telephone somehow picked up a radio station. After a couple of tries, I left via the side gate, wondering how I was going to get home. Suddenly, two cars roared into the Sanctuary at high speed. It was the managers, Patrick and Paul Robertson. It turned out that, whenever I dialed the number, the phone rang in the café. The old ladies, not having been informed of my presence, were scared witless, and called the Robertsons and told them there was an intruder on the grounds. I can't remember how I got home.
     Anyhow, the upshot of this investigation was to establish that koalas sleep an average of 19½ hours a day.

     Most of the remaining 4½ hours is spent eating. Eucalyptus leaves are a low nutrition diet, and a lot have to be consumed in order to produce enough energy to even sleep. According to a silly popular rumour, they are in a stupour from the drugs consumed in their diet. Nonsense, of course! No animal can be "drugged" by its own natural food. But it is true that the oils in eucalypt leaves - the ones they use to make disinfectants! - are highly toxic, and koalas are one of only two mammals - the other being the greater glider - able to eat them with impunity. It is also true that they are (normally) restricted to a relatively small number of eucalypt species.
     At Lone Pine the removal of the old leaves in mid-afternoon wakes them all up. The appearance of fresh leaves causes a veritable stream of koalas to flow down the trees and feed on the ground, then, as soon as the leaves are bound to the trees, those on the ground are instantly deserted. They feed for 60 to 90 minutes, after which feeding slackens off, to be resumed at odd hours later in the day. An individual will then feed for 20 or 30 minutes, only to recommence an hour or so later.
     The method of feeding is ritualised. First, a bunch of choice leaves is grasped in one hand (koalas are ambidextrous) and pulled to the mouth. The diner may then run its nose over the leaf and reject it if it is not to its fancy, but koalas are nowhere near as fastidious as popular legend makes out. The jaws then glide over the leaf and bite it off at the base, and the leaf is gradually worked lengthwise into the mouth by the rotary action of the jaws. Many of the older individuals tend to dribble, and their mouths and throats are stained yellow from the juice.
     Baby koalas are a joy to behold. An infant's first contact with solid food occurs when some of the leaves its mother is consuming happen to fall within its reach. Without using its hands, it takes a bite out of one, or else eats it without removing it from the stem. The next stage is when, by accident, it manages to hold down a leaf while still clutching its mother's fur. Later, it starts to grasp the leaf beforehand, but does not pull it towards its mouth.
     A cub at first bites anywhere on the leaf, rather than at the base. It thus becomes difficult to sever the leaf, and so it has to jerk its head vigorously back or to to the side, tearing large pieces out of the leaf. Also, because a leaf is so much larger for a baby, it is much more difficult to handle, and cub can often be seen flailing its hands around trying to steady a leaf which should have been grasped firmly in the first place.
     I did a statistical analysis to determine how a youngster's feeding habits gradually improve with age. The grasping action is used more often and the bite is directed more and more frequently to the base of the leaf, while concurrently fewer head movements are required to sever the leaf, and fewer hand movements to steady it afterwards. However, some things do not change, but appear to be inborn: the amount of sniffing of the leaves (once every four bites), and the proportion of lateral to backwards head movements (1:2, but adults use both very rarely.)
     Gravel probably adds calcium to their diet. It has actually been recorded in the caecum, or large "appendix" of a koala. In 739 hours I saw 13 cases of gravel being lapped up, like water, for up to 2½ minutes at a stretch. They also nibble and lick at the bricks and mortar (33 occasions), as well as other sundry items. I twice saw a certain male grab his neighbour's ear just as if it were a leaf, and chew it until it bled and the loudly protesting victim escaped.

     According to popular belief, the name "koala" means "doesn't drink" or "no water", and they are popularly said not to drink. So let me set the record straight. In Aboriginal languages, as in most other languages, including English, common animals have a name which is specific to themselves, not based on a combination of other words. Also, Aboriginal languages typically have roots of at least two syllables, and the verbs possess complicated endings relating to person, number, and tense. In other words, "koala" is simply too short to mean "doesn't drink" or "no water". In fact, the English name is a corruption of koolah or kola, from the Kathang language spoken between Telegraph point or Port Macquarie and the Hawkesbury River. In that language, it bears no similarity to the words for "drink", "water", or "no/not". The word provides us with various place names, such as Coolah and Mt. Colo, and there are similar terms in the languages nearby. For instance, Dharuk, the language of the Blue Mountains, called the animal kulan.
      Nevertheless, it is certain that they can go without water for indefinite periods in winter, and for several days in summer. I have seen them lick water from leaves, and this probably happens frequently in the wild. When a tourist boat arrives at Lone Pine, it is greeted by a German shepherd dog carrying a koala on its back. At other times, the dog lives in the main enclosure, and the koalas share its water. When they do decide to drink, they keep it up for an average of four minutes, with the records being more than 14 minutes.

     Their physiology allows them to conserve water to a remarkable extent. For instance, they urinate only about once a day. With few exceptions, this occurs during locomotion. The animal will halt, lower its rump to within 1 or 2 cm of the ground or tree branch, discharge a copious stream of urine, and then move on.
     Koala faeces are as dry as those of a camel's. They are dark, tapering, ovoid pellets 18 - 30 mm long and 35% - 60% as wide, and are always produced in multiples. Koalas defecate while resting, or even when asleep, but never when moving. They also do so when being handled, probably as a result of mild stress. And thereby hangs a tale. One of the keepers told me about a time he had a sore throat, and would reach into his pocket for the supply of Hudson's eumethol jujubes which he kept there. He also had to handle the koalas. Need I say more? In a moment of inattention, he discovered that a koala turd is about the same size as one of Hudson's jujubes, but it certainly doesn't taste like one!
     Adults produce an average of 76 faecal pellets per day, subadults 81, and mothers with their cubs from 77 to 113. How do I know? Well, the pens used to be hosed out every morning, before the visitors arrived, so all I had to do was jump into the pen armed with an automatic counter just before the cleansing commenced.

     A friend of mine once visualised my studies as sitting down and writing:
"He scratched himself."
"He scratched himself again."
Hind foot, showing grooming claws.
     But I did! However, I tended to be more specific in the information obtained - like how he stretched himself, where, and when. Koalas give themselves a scratch or two about 7 times every two hours. As with the other higher marsupials, two of the toes on their hind legs are modified as a double-clawed comb, which is held at right angles to the fur, and a couple of scratches applied. Otherwise, the hand will come down and a few scratches made with the claws by movements at the wrist, rather than the elbow. At other times they may chew or nibble at the fur. The foot scratch accounted for  88% of the observations, the hand scratch for 7%, and chewing 5%. I also tried gently plucking a few hairs, and was amused to watch a foot come up and aim a scratch at virtually any place within reach, only occasionally at the site of irritation.
     Koalas do not groom one another. In the Sanctuary they had no external parasites. In the wild, they are occasionally beset by ticks, but never fleas. Fleas lay their eggs in their host's bedding, and thus spread to those that share the bedding. That means fleas are restricted to animals which make nests. Dogs and humans have fleas, but not monkeys or koalas.

     On the ground koalas are flat-footed and slightly bow-legged, but use the two basic gaits of most mammals: walking by alternating a foreleg with the hindleg on the opposite side, and running by moving both forelegs, then both hindlegs, together. In climbing the same gaits are used, but because they tend to extend the forelegs fully while keeping the hindlegs flexed, they often have to break step for the latter to catch up. If a branch is inclined about 60 degrees to the horizontal, they will usually walk on the upper surface, but in a third of cases will use the under surface. Nevertheless, the weight is always suspended from the forelimbs, so they never descend head-first. Despite appearances, however, they are remarkably robust. I have seen one fall at least ten metres without being even stunned.
     Also, koalas can swim - after a fashion. Most four-footed animals can, and they use essentially the same limb movements that they use on land. We tend to call it the "dog paddle".

     If an animal sits in a gum tree and spends nearly all its time either sleeping, or eating leaves, how much effort does it need to take exploring its surroundings? The answer is: not very much at all. Although they often wander around their pens, the lack of interest shown in their surroundings is remarkable. A number of times I placed objects near the path of an individual only to have it totally ignored or, at best, granted a few perfunctory sniffs. On the other hand, sometimes a koala would approach my shoes, brief-case, or stool - objects which would normally be ignored - and give them a thorough once-over of sniffing and chewing. One wonders whether it was the scent of other koalas which interested them - although there shouldn't have been any such smell on my shoes. Such incidents occurred only during the breeding season. When moved to another pen, a koala may settle down almost at once, or else wander around exploring it for half an hour or so. In other words, their response to a change in the environment is entirely unpredictable. Curiosity may have killed the cat, but koalas are in no danger from that front.

So let's go back to
Part 1. Background
or forward to
Part 3. Bringing Up Baby
Part 4. Communication
Part 5. Sex
Part 6. Fighting
Part 7. Comments and References