Forage utilization by sheep and kangaroos in a semi-arid woodland

Abstract

The utilization of forage species by sheep and western grey kangaroos, and their contribution to the diets of those animals, were determined in a mulga (Acacia aneura) woodland in western New South Wales. Utilization was determined from measurements of forage yield, on pastures that were grazed by either sheep, sheep and kangaroos together or kangaroos, at a range of stocking rates. The sheep and kangaroos had similar preferences for the major grasses, with high utilization of species such as Monachather paradoxa and low utilization of the more fibrous species such as Eragrostis eriopoda. At times of forage abundance, annual and perennial forbs were a major component of sheep diet but a relatively minor component of kangaroo diet. Differences in species preference thus arose mainly in species that were uncommon or of seasonal occurrence. The overall diets of sheep and kangaroos were similar, with a year-round predominance of the same group of perennial grasses such as Thyridolepis mitchelliana. In the treatment where sheep and kangaroos grazed together, kangaroos had access to areas exclosed from sheep and their use of these areas increased with increase in stocking rate. Thus the exclosures received a similar grazing pressure by kangaroos alone, to that of the surrounding paddocks grazed by a mixture of sheep and kangaroos. It is concluded that there is direct competition between sheep and kangaroos for the main forage species. There are also long-term effects of high kangaroo populations on sheep production because the movement of kangaroos to rested paddocks negates any pasture management practice that requires periodic resting of pastures from grazing.