Dama Wallabies: Their history of colonization and control at Okataina/Tarawera

Abstract

Dama wallabies (Macropus eugenii) were liberated near the southern end of Lake Okareka in 1912. By the 1970s their numbers had built to high levels in the forests surrounding Okareka, Okataina and Tarawera and the damage they were causing to the forest understorey was marked. In 1984 the New Zealand Forest Service established a pair of ‘exclosure plots’ at Okataina designed to isolate the impacts of wallabies from those caused by deer. A decade later when the vegetation plots were remeasured, species diversity had increased by 142% where both deer and wallabies were excluded. Diversity had increased by 57% where wallabies were excluded and continued to decline by 7% where browsing was unrestricted. Between 1988 and 1999 three aerial poisoning operations and some ground based pest control, targeting wallabies and possums, were carried out around Okataina and the Makatiti Dome. Though these operations were highly successful at reducing wallaby numbers (93-95% reductions based on cleared-plot faecal pellet counts) remeasurement of permanent 20x20 metre vegetation plots showed no response in the forest understorey. To some extent this is not surprising as the control operations were effectively ‘one-offs’ in separate areas and only limited follow-up control took place.