The Distribution and Abundance of Kangaroos in relation to Environment in Western Australia

Abstract

Red and western grey kangaroos were surveyed from the air in Western Australia during the winter of 1981. The area covered, 1 528 000 km2 or 61% of the State, excluded only the Kimberleys in the north and the Gibson and Great Sandy Deserts of the interior. Hence almost all kangaroo range within the State was surveyed, to provide an estimate of 980 000 reds and 436 000 greys. Densities were much lower than those of the eastern States. Red kangaroos were most abundant in mulga shrubland, chenopod shrubland and tussock grassland, and least abundant in hummock grassland. Densities were associated strongly with land-use categories, being high in areas used for extensive sheep grazing and low in vacant Crown Land and arable land. In contrast to reds the western grey kangaroos were confined to the south and west of the state, their distribution being related more directly to climate than to vegetation or land use. They live in the winter rainfall zone. We suggest that their restricted breeding season results in peak nutritional demands associated with lactation, and hence energy requirements, being synchronized with the spring flush of pasture following winter rains. Approximately 14% of the red kangaroo and 8% of the western grey kangaroo populations in Western Australia were harvested legally in 1981.