The abundance of red kangaroos, Megaleia rufa (Desmarest), in central Australia.

Abstract

Aerial surveys using stratified random sampling were used to estimate the numbers of red kangaroos, Megaleia rufa (Desmarest), on about 4000 square miles of central Australia, once during drought, and again 6 months later after good rains had fallen. Sampling involved varying width of transects along their lengths to suit viewing conditions over various types of vegetation. The method of statistical analysis is provided. The number of kangaroos on an area depended on the availability of green herbage and shady trees. During the drought, kangaroos congregated near open plains and watercourses where green grass (Eragrostis setifolia and Astrebla pectinata) persisted; they reached densities of eight-nine per square mile. After the rains, they dispersed into the surrounding woodlands where green herbage was temporarily abundant. There were never many kangaroos on spinifex tracts which have few shady trees. The kangaroos' nomadism is thus linked with their search for food and shelter. The tendency for kangaroos to cluster was highly correlated with their density on an area. The total numbers of kangaroos on 2642 square miles of the study area changed from 3927 during the drought to 4914 after the rain, probably as a result of immigration. The environment of kangaroos is ameliorated by cattle cropping the long dry grass of the open plains, causing it to sprout green shoots. Large areas where kangaroos can find food during drought have thus been provided for them.