In captivity, koalas are mostly very placid, easy-going creatures, but when they fight, they really fight. In all cases the basic pattern is the same: an arm is thrown over the victim, which is then bitten on whatever part of the anatomy is closest.
Literally hundreds of minor squabbles were recorded. These occur when an individual tries to climb past another. They may be prolonged, but are usually quite half-hearted, and often the victim not not deign to take notice of the bite, but simply continues climbing. Interestingly, an individual is more likely to be bitten if it approaches from the side or front, where it can be seen, then from the rear. Sometimes, if a koala finds its path blocked by a sleeping companion, it will give the unsuspecting fellow a bite, and an individual sitting near a squabbling pair runs the risk of being bitten.
Aggression does not appear before the age of 11 months nor, generally speaking, are cubs the target of aggression. As stated before, all adults are very tolerant with young. Towards humans Lone Pine koalas are very tame, though a mother may give a few nips if her pouch is tampered with. But nobody should ever try to touch a wild koala. Their jaws are strong and, although the powerful claws are not used in combat, they could cause severe damage if a frightened animal were to try to cling to its handler.
One fight lasted several hours, but normally ten minutes was the limit. It would end in one of three ways: (a) the combatants were separated by the staff, like fighting dogs, (b) the loser broke and ran, or (c) the winner forced his victim onto his back, biting savagely at his belly, whereupon the loser, unable to escape, screamed loudly, thus causing his conqueror to desist. Generally, the victor would proclaim his triumph by bellowing.
Fights could break out completely unexpectedly, and without provocation, but were much more likely to involve strangers newly introduced to a pen. Apparently, males get used to regular companions. Fights directly over females did not occur, but males did get aroused by the sound of aggressive interactions elsewhere, and a third party would sometimes throw himself into a battle already in progress.
Too much can be made of male aggressiveness. In 739 hours only 27 really violent fights were recorded, despite the large number of males potentially available. One male had a piece of skin torn from his wrist, and another received a gash on his nose, while two other possessed cauliflower ears, but normally the koala's dense wool gives him perfect protection.
Females are more aggressive, though less violent, but the situation is peculiar. Normally they are quite placid but at times, for reasons completely unknown, they can become exceptionally aggressive. This is most common when it can be deduced that they are undergoing hormonal changes, such as when pregnant, or during or after weaning a baby, but no rules can be laid down. At such times the female snarls, wails, screams, or even bellows whenever another individual approaches, or even simply moves around nearby. If the other koala continues to approach, it will be attacked, often most savagely. Such an attack will inevitably force another female to retreat, but a male may fight back. Almost 600 such aggressive vocalisations were recorded, of which 60% were directed at adult males, including the times when the male was actually assaulting the female.
There were 87 minor fights recorded between males and females. A half-dozen of these were described as "pestering", in which the male made a nuisance of himself following a female, giving her light nips, and occasionally sniffing her pouch or genitals. In fact, once three males pestered a female for hours with hardly a break, constantly forcing her to defend herself, and occasionally trying to mate with her. It sounds a bit similar to courtship in other marsupials, but this is unlikely to be the case, since it never succeeded nor, except in the one case just mentioned, was any attempted copulation directly preceded by pestering.
However, in 40 cases a female was brutally attacked by a male, who often forced her to the ground and savagely bit at her abdomen, until her screams at last forced him to withdraw.
Why this should be so is a mystery. The male does not appear to gain anything from it. In a few cases it is likely he was rebuffed while trying to mate. In other cases his fury was provoked by the female attacking him as he attempted to pass. Yet it cannot be doubted that the aggressive vocalisations of a female inhibit a male. In 127 cases he retired without physical aggression taking place at all. Even if the male does decide to advance, he tends to do so hesitantly, stopping in his tracks every time she vocalises.
However, it seems certain that in many cases the male's intentions were at first completely peaceful, and he exploded into violence only when she vocalised at him. In such cases the vocalisations would appear to have been counter-productive. To make things more complicated, there were other occasions when the attack was completely unprovoked, commencing even before the female had a chance to make a sound.
In short, there is neither rhyme not reason in the males' aggressive actions towards females. Some of them most likely had a sexual basis, since they is considerable evidence of these two drives acting at the same time. However, only a fraction of the data can be explained in that manner. It is possible the crowded conditions of captivity result in excess aggressive stimuli. No doubt, too, aggression is controlled partly by the internal state of the animal. If a male is feeling mildly aggressive at the time a female snarls at him it may well provoke him into action; if not, then he simply retreats.
An important point is that aggressive vocalisations are purely defensive. Females only attack if approached, but even when unprovoked attacks are made by males, no vocal signals are given beforehand. Indeed, males have no behaviour patterns involved in deterring other animals from approaching in the first place. Not only that, but they possess no appeasement ritual by which a subordinate can prevent itself from being attacked. Indeed, they do not even have a dominance hierarchy as such. All this suggests that, despite the ease with which they get on together in captivity, they are not really adapted to living in groups.
Lastly, let it be repeated that the bursts of energy described above are very much the exceptions to the rule. For the vast majority of time they are inactive and unassuming.
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Part 1. Background
Part 2. Basics
Part 3. Bringing Up Baby
Part 4. Communication
Part 5. Sex
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Part 7. Comments and References