Feral goat control in Egmont National Park, New Zealand, and the implications for eradication

Abstract

Feral goats in the 34 169 ha Egmont National Park (North Island, New Zealand) have been subject to sustained ground-based hunting with dogs since 1925. We analysed trends in hunting success from 1961 to 1999. During 1961–86 the catch per unit effort (CPUE) declined from 7 kills hunter^–1 day^–1 to <1 kill hunter^–1 day^–1. Since 1987 the CPUE has been maintained at low levels. The key impediment to switching from a strategy of sustained control to eradication is whether or not all goats can be put at risk. We suggest that managers test this experimentally in part of the park before embarking on an eradication programme. On the basis of an empirical estimate of r_m and an assumption of logistic growth, we estimated the current population to be ~1047 animals. Removing 50% or 90% of the population annually would eradicate the population in >50 years or 12 years, respectively. Annual immigration of goats would prevent eradication under all scenarios.