A Pocket Full of Rye

“A Pocket Full of Rye”
So goes the old nursery rhyme, Sing a Song of Sixpence.

Perhaps we might be forgiven for applying this use of the word pocket to the pouch of the marsupial animals, for it contains not only the infant but also the food supply of mother’s milk. What a boon this must be when travelling!

In the last issue, we looked at the marsupial kangaroo family who carry their young safely in their pouches across the miles they cover with ease. In this issue, we look at another family group, the koala and the possums, who also pocket their young as they climb and swing their way through the branches of the forest canopy with equal ease. Both are arboreal animals and, not surprisingly, are herbivores.

The Koala.
The koala, which is perhaps one of the best-known of the Australian wild ones, spends his life in the gum trees (eucalypts) of this country. He depends upon them entirely for his food supply and his sleeping quarters. Only occasionally does he descend to the ground, to change to another tree, for example He spends more of his time, asleep than awake, for a very good reason.

His diet is restricted to certain varieties of eucalypt leaves. These leaves contain large quantities of toxins. As the leaves contain a large amount of oil that makes them unpalatable, they are usually avoided by the majority of other animals.

The Koala, however, has adapted himself to such a diet. His teeth and jaws are powerful grinders. His large hind gut contains bacteria that extracts all possible nutrients from the leaves, and his liver is capable of filtering out the toxin.

As his nutrient intake is low, he needs to eat large quantities of leaves in order to survive. However, should he eat to excess, his liver would be unable to function properly and the koala would die from toxicity.

To adjust this delicate balance, and limit the amount of leaves consumed, energy has to be saved. Here is the reason behind the fact that koalas just have to spend most of their time sleeping, 16 to 18 hours per day curled up, wedged in the fork of a tree. This is why they are looked upon as being most docile, cuddly animals.

But beware! All is not always what it appears!

More or less a solitary animal, two adult koalas never share the same tree when eating.

In the mating season, they awaken themselves from their lethargic state and become very aggressive. And they are weighty animals – up to 14 kg in the southern states, 9 kg in Queensland. They are fiercely territorial. They normally share their territory with up to three females. Should another male approach one of these females during the mating season, a noisy battle of teeth and claws begins. On occasion, the opponent can even be knocked from the tree. Humans beware, claws that ensure safe climbing and tree navigation become vicious weapons that can tear human skin to the bone.

The koala is comparatively late in beginning its breeding cycle, somewhere between their second and fourth years. They usually produce one babe annually.

The pouch of the koala opens at the bottom, facing out towards the rear of the animal. This is the reverse of the other tree-loving marsupials. This positioning is usually associated with the marsupial earth-tunnelling animals, like the wombat, bandicoot or mole, its purpose being to divert the danger of earth getting into the pouch. This is a curiosity. There are some scientific theories as to the reasons for this.

When the time comes for the koala babe to climb out of the pouch, then, like other arboreal mammals, it grips its mother’s loose furred skin and climbs on to her back for safe travelling. At sleeping time, it nestles cosily in its mother’s arms, the very picture of perfect tranquility.

Possums.
There are many different families grouped under this name, including brushtail, ringtail, pygmy possums and gliders, as well as the cuscus of the tropical forests in far north Queensland. All are marsupial herbivores, some are both arboreal and terrestrial.

Originally, possums inhabited the rain forest areas. Some, however, made the transition to the more open eucalypt forests. Today, many of them may be found living in urban parks and gardens.

The common brushtail is such a one. He has become most bold and will take up residence in the roof space of houses and other convenient nooks and crannies that buildings present. Many folk place nesting boxes for them, fastened to a tree or post. Natural holes in trees are often in short supply for homes, so we help out these friendly fellows with free lodgings.
Ringtail possums live in the rain forests of the east and southeast coastal strip of the mainland, including Tasmania. They use their long tail as a climbing aid, coiling it around a branch and swinging across to gain purchase of another.
In the southern areas of its range, it builds, in a thickly shrubbed area, a large spherical ‘drey’ from twigs, broken bark and leaves. In the north, it prefers a tree hollow lined with leaves. The green ringtail of the rain forests of northern Queensland makes no shelter for itself, but simply curls himself up on a branch. He is so well camouflaged that it is difficult to catch sight of him.
Glider possums are a charming little group. They have loose skin – their gliding membrane – attached to their ankles and wrists that opens out enabling them to leap and glide from one tree to another. The sugar glider, for example, can glide up to 90 m. They are quite a sight to watch airborne, resembling fairytale magic carpets.
The sugar glider, just before reaching the tree he has targeted, deliberately stalls, dropping his hindquarters so that he hits the trunk with all four feet stretched to grab hold.
These are but a few of the various species of Australian arboreal animals. Many of them are becoming rare as bulldozers ravage their habitats. Happily, Australians value their unique native animals and do their best to preserve and foster them against the dangers that beset them all too frequently.

– Sylvia Roff-Marsh

published: July 2007

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