The plants eaten by sheep and by Kangaroos grazing together in a paddock in South-western Queensland

Abstract

It has been found possible to identify plants and to estimate their relative proportions by volume in the stomachs of sheep and kangaroos (both the red and the grey species). The method involves grinding stomach contents to a fine powder and isolation of particles of a given size range by differential sieving. It is shown that kangaroos are reasonably sedentary so that comparison of the botanical composition of the stomach of free-roving kangaroos with those of sheep restricted to one area, is valid. The three species of herbivore, during the study period of 1 yr and under the conditions described, were found to have food preferences. These preferences were specific enough to justify the conclusion that the plants of the habitat and the three species of animals constitute an ecosystem. There is no evidence, pound for pound body weight, that kangaroos eat more than sheep. Large numbers of kangaroos could have a detrimental effect on wool production since they eat considerable quantities of dicotyledons which are rich in protein and which constitute about 50% of the sheep's intake. Kangaroos, although ostensibly adapted for browsing, never ate mulga or berrigan. Sheep, however, browsed both these trees.