Possum (Trichosurus vulpecula) diet in a mast and non-mast seed year in a New Zealand Nothofagusforest

The annual diet of possums (Trichosurus vulpecula) during both a beech (Nothofagus) mast fruiting year and a non-mast year in the simple beech forests of the North Branch of the Hurunui Catchment, eastern South Island, New Zealand, was determined by sorting the contents of 270 possum stomachs, collected between December 1999 and December 2001. Beech flowers and seeds contributed 46.1% to annual diet during the mast year, but were not eaten during the non-mast year. Beech foliage and bark made up 13.2% and 45.0% of annual diet in the mast and non-mast years, respectively. Fungi, herbs and grasses together comprised 23.1% and 42.4% of the annual diet in the mast and non-mast years, respectively. Diet varied with altitude and distance down the valley, principally in the relative contributions of foods from the three beech species present, which reflected local canopy composition. Other local food sources such as valley-floor herbs and grasses also contributed significantly to local diet. Although heavily reliant on beech species, possums are unlikely to have a significant impact on beech flower and seed production, or on the health of beech trees because of possums’ low abundance and the large beech biomass at this site. Recognised possum-preferred foods such as Aristotelia serrata, Fuchsia excorticata, Hoheria glabrata, Raukaua simplex, Elaeocarpus hookerianus and mistletoes (Peraxilla tetrapetela and Alepis flavida) were all strongly preferred by possums but, because of their scarcity in the study area, were only eaten in small quantities.