The kangaroo conundrum: home range studies and implications for land management.
The movement of native herbivores onto agricultural land is a key management issue world-wide as they may compete with domestic livestock for pasture and contribute to overgrazing and soil erosion. Eastern grey kangaroos Macropus giganteus are viewed as a problem species in temperate south-eastern Australia, where high-density populations in reserves encroach on nearby farmland. This study examined home range size and use in M. giganteus across different types of land use and in relation to population density and pasture availability. Farmland adjacent to either radiata pine plantations or reserves supporting high-density populations of M. giganteus was subject to frequent incursions by kangaroos moving onto farmland to rest or graze. However, animals from reserves moved on average only 135 m onto farms. Home ranges of M. giganteus were significantly smaller in the reserves than in farm study sites where population densities were lower. At reserve sites, home range size was limited by higher population densities and limited opportunity for dispersal across surrounding open farmland because of a lack of cover. Home range size was not affected by resource availability. Where suitable vegetation cover occurred on farmland (e.g. woodland remnants or scrub), M. giganteus occurred as resident or roving small mobs. This may be seen by farmers as a disincentive to preserve remnant vegetation as it can provide habitat for unwanted native wildlife. Home range attributes of M. giganteus suggest the species could be controlled by culling. However, recolonization occurs quickly and little is known of dispersal. Synthesis and applications. Population density, presence of cover and reluctance to disperse across cleared landscapes are key factors influencing kangaroo home range size and use of adjacent farmland. Currently, little incentive exists for farmers to preserve remnant vegetation, as it may be regarded as providing habitat for unwanted or 'pest' kangaroos. Given the potential importance of remnant vegetation on private land for the conservation of plants and other species of wildlife, government incentives and compensation programmes may be required to limit land clearing on farms and to encourage improved pasture management.