Diet and Food Preferences of White-Tailed Deer in Northeastern Stewart-Island

The diet and food preferences of white-tailed deer (Odocoileus virginianus) on north-eastern Stewart Island are described from the analysis of 160 samples of rumen contents collected between 1979 and 1985, and vegetation surveys in 1975 and 1976. Deer browsed all the hardwood trees, but few shrubs, ferns, or podocarps. Woody plants comprised 85.1 % (dry weight) of annual diet. Broadleaf (Griselinia littoralis; 34.6%) and supplejack (Ripogonum scandens; 18.6%) were the most important foods, all other species comprising less than 5%. There were no differences in diet between the sexes and only small differences between areas. Fawns, however, ate more supplejack fruit and less shrubs, ferns, herbs, and grasses than older deer. All deer ate more supplejack fruit and foliage of subcanopy trees, and less broadleaf, shrubs, and ferns in winter than in other seasons. Food appeared scarcest in summer. Deer probably obtained most of their food as fallen leaves and fruit; this is discussed in the context of the long term trends in forest structure and deer carrying capacity that follow deer colonisation. We believe the main hardwood food trees will gradually die out, resulting in a substantial decline in the carrying capacity of the forest.