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

Abstract

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.

Wildlife management aims and ecological processes: A case study of kangaroos

“…It is simplistic because it assumes no maximum annual r , which is an important and useful parameter (Hone et al ). A linear correlation of r and rainfall has been reported for kangaroos (Cairns et al , Pople et al ) and is equivalent to the linear part of the ramp model of Bayliss ().…”

“…Long‐term data on food supply are often not available and therefore rainfall is often used as a surrogate for food supply because of the positive association between the 2 variables (Caughley et al ; Bayliss , ; Caughley ; Cairns and Grigg ; Lethbridge and Alexander ). In kangaroo species, annual r and long‐term trends in populations are not correlated (Cairns et al ) or they show weak to strong relationships (Jonzen et al , Pople et al ) with antecedent rainfall, with a time lag depending on the population studied.…”

Landscape discontinuities influence gene flow and genetic structure in a large, vagile Australian mammal,Macropus fuliginosus

“…1998). Gene flow in M. fuliginosus may be further restricted by the high temporal variation (175–200%) in the densities of populations spanning this region (Cairns et al. 2000).…”

Spatial patterns of kangaroo density across the South Australian pastoral zone over 26 years: aggregation during drought and suggestions of long distance movement

“…Fluctuations in kangaroo numbers and their relationship with food supply have been described in a number of studies (e.g. see review by Cairns 1989; also McCarthy 1996; Cairns et al . 2000; Jonzen et al .…”

“…Harvest quotas can therefore be set reliably only for regions that are considerably larger than 10 000 km 2 and so precision is generally < 40%, given the sampling intensity used in aerial surveys of kangaroos (e.g. Cairns et al . 2000).…”