DAMAGE TO VICTORIAN EXOTIC PINE PLANTATIONS BY NATIVE ANIMALS

Abstract

SUMMARY Serious local and seasonal damage to exotic pine plantations is being caused by possums of two species, the black-tailed wallaby, and the allied rat. These animals attack the trees to obtain food material in the combial layer. Damage consists of bark stripping and girdling or partial girdling. Severe damage results in the death of the tree. Recovery may take place after less severe damage but the tree becomes deformed and its value as timber is substantially reduced. Several factors are involved, of which the most important are availability of ground cover and food material. The presence of the former makes the forest a suitable habitat for small mammals, and limitations on the latter cause them to attack the trees in times of food shortage. Proximity of native vegetation and water is also important as the mammals tend to harbour in such areas. Removal of cover would reduce the damage. Adjustment of the habitat is preferable to destruction of the animals. If this proves ineffective, the offending animal population may be eliminated in local areas by poisoning and trapping rats, and trapping and snaring possums and wallabies. Poisoning of the latter two is prohibited under the Victorian Game Act 1928. Numerous references to overseas elimination of unwanted populations by poisoning are available. Local field trials on types of baits and methods of poisoning are essential to determine which are most effective on the species concerned. It is also necessary to consider what desirable native species are likely to take the baits selected and ensure that they are safeguarded.