Herbivore diet in a semi-arid Eucalyptus populnea woodland. 1. Merino sheep

Abstract

The diet of sheep was recorded by direct observation in a shrub-dominated Eucalyptus populnea woodland between Nyngan and Bourke, N.S.W., on 7 occasions over a 2-year period. Different nutritional opportunities were provided by the effects of rainfall on 3 contrasting grazing treatments. The sheep did not graze equally over the whole area available but foraged selectively so that they encountered unacceptable plants rarely. In particular variable spear grass (Stipa variabilis) was avoided once the inflorescence had emerged and only extreme hunger pressured sheep into foraging in dead stands of this grass.matured, sheep ate firstly increasing quantities of perennial forbs and then mulga (Acacia aneura). When these foods were depleted, sheep subsisted on dead perennial grass, tree litter and broad leaf hopbush (Dodonaea vlscosa). All other shrub species were unacceptable. The ability of sheep to forage successfully during dry periods put excessive pressure on perennial grass, causing it to die out. I suggest this has contributed to the increased frequency of shrub establishment in the poplar box woodlands since they have been used for pastoral production.