The control of pest wallaby populations

Two species of wallabies present in Tasmania, Macropus rufogriseus and Thylogale billardierii, have been demonstrated to cause significant economic loss to the grazing industries. Preliminary investigations into quantifying the competition between wallabies and livestock have shown losses of 11.3. to 17.1 kg dry matter per ha per day, which can be converted to a gross cost of between $140 and $400 per ha per year. The need for the control of wallaby populations arises from these potential losses and will be justified from an analysis of the anticipated benefits and the anticipated costs. One method of wallaby control that is commonly used in Tasmania is by poisoning with sodium monofluoroacetate (compound 1080). T. billardierii were shown to be susceptible to poisoning techniques developed for rabbit control. That is they readily find and consume chopped carrot bait distributed in a shallow furrow and are sufficiently sensitive to 1080 to be poisoned by a toxic loading of 0.014%. M. rufogriseus populations are however not as readily controlled using the same technique. The acceptability of chopped carrot bait to M. rufogriseus is not as good as that of dry bran/pollard bait in spring when there is a plentiful supply of green pasture available. Bran or pollard bait is therefore recommended as an alternative bait for wallaby control. Although there is no significant evidence of birds eating this bait, it is considered by wildlife authorities that pelleted bait may be less attractive to birds. These were not found to be well accepted by wallabies although are commonly used in New Zealand and other Australian States so are worthy of further investigation. Field investigations have shown that for the control of M. rufogriseus by poisoning with 1080 no significant differences in mortality rates could be obtained by (1) using 0.028% 1080 on bait compared to the normally recommended 0.014%, (2) using or not using a furrow for marking the bait line, (3) baiting with chopped carrot or dry bran or pollard, or (4) placing the bait line in the bush compared to about 20 m into the paddock. It is recommended that when attempting to control M. rufogriseus by poisoning, control should take place in summer or autumn when alternative food is not so readily available and that particular attention should be given to adequately free feeding and providing plenty of bait for all wallabies present. The concentration of 3.080 on bait should remain at 0.014%. Further investigations are required to ascertain whether surviving wallabies have eaten any of the bait, or whether the mortality rate can be improved by other changes to the poisoning routine, such as repeated poisonings. The protection of crops from wallabies by the use of electric fences is a promising alternative to poisoning. An effective fence must be evenly graded and have the lowest wire no more than 75 mm above the ground to prevent wallabies from creating a runway under the fence. The most effective fence design so far tested for wallaby control consists of six wires all with 75 mm spaces and the lowest 75 mm from the ground. The second, fourth and sixth wire from the around should be electrified. Further research is required to report in more detail the economic effects of competition between wallabies and agriculture, to further assess the effectiveness of improved poisoning techniques, and to further investigate the use of electric fencing for wallaby control.