Preferences, selection and damage to seedlings under changing availability by two marsupial herbivores

Abstract

Preferences for and damage to seedlings used in commercial forestry in Tasmania, Australia, by brushtail possums ( Trichosurus vulpecula) and Tasmanian pademelons ( Thylogale billardierii) were measured in paired-species feeding trials with captive animals. Both possums and pademelons consistently ate foliage more than stem for all seedling species examined. Possums showed significant interspecific foliage preferences more often than pademelons and they often had opposite preferences to pademelons. For possums, Eucalyptus nitens was one of the most preferred species, whereas for pademelons, Acacia melanoxylon and Pinus radiata were preferred. At low damage levels, possums ate the apical bud of seedlings more frequently than pademelons. A non-linear regression model was developed that describes the depletion of two food types by herbivores. A conditional selection index comparing two plant types was derived from the model, allowing selection to be quantified at any stage in the resource depletion process. Results are discussed in relation to the per capita impact of the two herbivore species, the development of non-lethal methods for managing browsing damage and the use of indicator plant species for triggering management options.