Western grey kangaroos, Macropus fuliginosus, in the South Australian pastoral zone:: populations at the edge of their range

As part of a large-scale monitoring program linked to the management of kangaroos in the South Australian pastoral zone, the western grey kangaroo populations have been surveyed annually with fixed-wing aircraft over the 15-years-period 1978-92. Western grey kangaroos are restricted in their distribution to the southern regions of the pastoral zone. During the period of the study, western grey kangaroo numbers showed no long-term trends, but did show some marked fluctuations, principally in association with a severe drought. Despite this, and unlike red kangaroos in the South Australian pastoral zone, no consistent, direct association between changes in western grey kangaroo numbers and antecedent rainfall could be demonstrated. The postulated reason for this is that most of the regional western grey kangaroo populations examined in this study were low-density populations at the edge of the range of this species. Outside of drought, these populations are likely to be limited by factors other than food, such as climate and unmodified resources in the form of suitable habitat. Also, because boundary populations may well only be maintained by constant loss and recolonisation, local extinctions associated with drought may result in extended delays in the re-establishment of populations in marginal areas. Over the period 1978-92, these populations were harvested commercially at annual rates of 5-25%, which were, on the whole, considered to be below the rates suggested to be maximum and sustainable.