Impacts and Economics of Wildlife Browsing on Tasmanian Pastures

The clearing of land for agriculture and the establishment of forestry plantations in Tasmania has led to changes in the distribution and population density of mammalian wildlife species. Populations of Bennett’s wallaby, Tasmanian pademelon, and common brushtail possum appear to have significantly increased over the past 50 years. Management of these and other species, including Forester kangaroo and introduced fallow deer on private land, is a contentious issue for landowners, animal welfare groups, and the government. Many farmers believe that browsing by native wildlife on pastures is significant and results in a considerable financial impost. However, limited research has been undertaken to quantify this wildlife browsing. The main control methods for these wildlife species include exclusion fencing, shooting, trapping, and poisoning. In 2005, the use of the poison 1080 (sodium monofluoroacetate) to kill wildlife was banned from use on public lands, and the Tasmanian Government plans to cease all use by 2015. This study investigated the effects of browsing wildlife on pasture within this region. We used a split plot design, consisting of 2 main treatments with 9 sub-plot treatments, to determine browse impact. Significant reductions in pasture biomass were recorded. The severity of browsing was affected by distance from native vegetation and also varied seasonally. Browsing damage declined with distance from native vegetation edge and was best explained by a logistic relationship. Browsing damage was severe during winter 2008 and varied between 100% at 25 m and 68% at 800 m from native vegetation edge. Browsing wildlife had the least impact during spring 2009 and reductions varied between 64% at 25 m and 0% at 800 m from native vegetation edge. The availability of pasture was found to be a determining factor in the distance and direction that wildlife would travel to browse. Browsing by wildlife also resulted in a reduction in ground cover