Seasonal variation in the impacts of brushtailed possums (Trichosurus vulpecula) on five palatable plant species in New Zealand beech (Nothofagus) forest

Abstract

The seasonal variation in possum browse and foliage cover of five possum-preferred species was quantified and studied in northern Westland, New Zealand over a 24 month period. Four of the five species (Pseudopanax simplex, P. colensoi, Aristotelia serrata, and Elaeocarpus hookerianus) showed marked seasonal patterns in both browse and foliage cover, with maximum browse evident in winter/spring when foliage cover was at a minimum. There was very little browse and no seasonal pattern in foliage cover for the fifth species, Pseudopanax crassifolius. In the season of maximum browse there were significant negative correlations between browse and foliage cover for the four impacted species suggesting that the changes in foliage cover were caused by possum browsing. Mortality was highest in the two most heavily browsed species (P. simplex and P. colensoi). This seasonality in possum browse needs to be accommodated when designing long-term surveys of possum impacts.