Red kangaroo (Macropus rufus) dynamics: effects of rainfall, density dependence, harvesting and environmental stochasticity.
Change in the number of red kangaroos (Macropus rufus) in the South Australian pastoral zone is related to rainfall and population size. These relationships are used to assess effects of harvesting red kangaroos by predicting the change in the risk of population decline and explosion under a range of harvesting regimes. The predictions account for the combined influences of rainfall, density dependence and environmental stochasticity. The method illustrates the importance of considering environmental stochasticity when assessing impacts, and how risk assessment may be used to assist wildlife management. Sustainable harvesting rates will be overestimated if environmental stochasticity is ignored. Because of uncertainty about the response of the red kangaroo population to extremes of rainfall, it is difficult to be certain of the effects of harvesting red kangaroos. The relationship between rainfall and population size depends on the scale of observation. The previous year's rainfall is most closely related to changes in population size over the whole pastoral zone. Over small areas, summer and autumn is the most critical rainfall period.