A comparison of 3-parameter, single-species population models, in relation to the management of brushtail possums in New Zealand.

A range of published 3-parameter, single-species models are compared using possums in New Zealand as an example. Most models yield similar population growth curves and similar estimates of maximum sustainable yield (MSY). A new model of competition for refuges, and interactive models of competition for food, both yield growth curves peaked to the right. In the second case, the relationship between the shape of the curve and the parameters of the interactive model is described. Three management consequences of asymmetric (rightward-peaked) growth as opposed to logistic growth are discussed. First, where the animal is a pest a greater control effort is required to reduce density. Second, for sustained yield harvesting the best policy is an adaptive one which initially requires no knowledge of the shape of the growth curve. Third, sustainable yields may be 50% higher than those predicted by the simple logistic model.