Zoologist may solve koalas' gum problems
By Julian Lee Scientists have known for years that koalas are fussy eaters, however one ANU zoologist believes he knows how these gum gourmets choose between different trees. PhD student Ivan Lawler, of the Division of Botany and Zoology, has studied a class of recently identified toxins - diformyl phloroglucinol compounds (DFPCs) - that are responsible for determining which trees will be eaten by leaf-eating mammals such as koalas and possums. "The findings of my study explain why some trees of an edible species are left alone, while others are ravaged," Mr Lawler said. After seeing possums leave one tree and risk life and limb to cross a busy road to feed on the same type of tree, Mr Lawler's supervisor, Dr Bill Foley, realised there must be important differences between trees of one species. "Animals do not care what a tree species is called, they use their sense of smell and taste to determine which trees will be edible," Mr Lawler said. Studying toxic DFPCs in trees, Mr Lawler found that as the concentration increased, possums and koalas ate fewer leaves and avoided trees with very high concentrations. He also found that terpenes - the chemicals which give eucalypts their characteristic smell - rose with increasing DFPCs. While terpenes were believed by scientists to inhibit feeding, Mr Lawler has proven that in isolation they do not. Instead he believes terpenes stop possums and koalas from eating leaves by providing an aromatic indicator of the presence and amount of DFPCs. The results of the research will be valuable for both forestry and conservation. "A significant number of forest plantations never get off the ground because the seedlings are eaten before they can mature. Also, it has never been explained until now why some areas with suitable species of trees do not support mammals," Mr Lawler said. Mr Lawler believes that, by breeding trees with particularly high DFPCs, foresters could grow plantations which would be inedible to possums and koalas. Conservationists, on the other hand, could identify forest areas that contain trees with low DFPCs which should support possums and koalas. Mr Lawler has developed a cheap and simple method of identifying the level of DFPCs a tree contains. The technique is based on Near Infrared (NIR) spectroscopy, widely used in agriculture but under-utilised by ecologists, Mr Lawler said. "Ultimately we hope to take to the skies with NIR scanners, allowing very rapid determination of DFPCs in all the trees of a forest," Mr Lawler said. For those on the ground however, Mr Lawler has a simpler method for determining which trees contain DFPCs. "The smellier the tree, the more DFPCs it is likely to have," he said.