Let there be a big eucalyptus, but not too much
When it comes to food, koalas have a problem. The only food she eats are the leaves of the eucalyptus tree, but these leaves also contain toxins in large quantities, which can cause vomiting. Scientists from the Australian National University tested how the koala feeds without vomiting. The answer, they report in the latest issue of the journal "Nature", is that these marsupials are very picky about the tree on which they eat.
The researchers examined all 857 eucalyptus trees (of two species) planted over an area of approximately 81 dunams in the koala reserve on Phillip Island in southeastern Australia and tested their nitrogen content (a measure of nutritional value) and toxins (a compound called FPC, which the plant produces to protect itself from koalas and other animals).
The researchers also examined data collected over ten years by a group of koala caretakers, who kept a monthly record of the trees in the park where the koalas had settled. Koalas do not move from tree to tree to eat. For them, the tree they are sitting on is their only dinner.
The researchers believed that the koalas would choose the big trees because when the amount of leaves is greater, the food source is richer and the shelter is safer. The collected data proved that the animals do prefer big trees, but not too much. It turned out that the bigger the tree, the higher the concentration of toxins. And the koalas, it turned out, stayed away from the trees where the highest FPC levels were found. They also kept a distance from trees whose nitrogen levels were low.
