The perfect lands for koalas are the river flats and lands with volcanic soils. These flood plains and fertile soils produce koala food trees full of life.
To say, “All that koalas need is trees” is putting things simply. While many see the koala as an animal that does not do much – simply eating, sleeping and breeding – this is not true. Koalas are complex, and they are particular.
Koala life follows a regular annual cycle. Through the summer months koalas mate, give birth; in the autumn and winter months young develop in pouch and later on their mother’s back, pap feeding. Males bellow and scent mark in the spring, fighting and mating into summer…and so on.
The main source of food for koalas in South East Queensland is Eucalyptus tereticornis (Red Gum or Blue Gum), and in swampy areas it is Eucalyptus robusta (Swamp Mahogany). Australia wide, of more than 700 species of eucalyptus, there are only 25 species of eucalyptus that koalas can eat. However, the actual species eaten by koalas varies from area to area – those food tree species selected in one area may be totally different from those selected elsewhere.
Koalas need a full suite of leaves to make up a balanced diet. Koalas prefer to eat the tips of fresh new growth, where there is more nutrition and less cellulose and tannin. Dr Steve Johnston of the University of Queensland says that when you look at the biochemistry of koala food trees, the smaller trees have limited access to water and switch their carbon off, which is unpalatable for koalas. So koalas will not use younger trees for food. Generally a tree must be 7-10 years old with a minimum diameter of 10 centimeters at chest height before koalas will use it for food.