Commissioned by: West Coast Conservancy

A method for assessing the palatability of selected threatened plant species to brushtail possums (Trichosurus vulpecula) is proposed, based on a brief review of relevant literature. This report was prepared as external unprogrammed science advice for Westland Conservancy, Department of Conservation. OBJECTIVES Develop a procedure for assessing the palatability of particular threatened plant species to possums. Discuss the extent to which such results might be extrapolated to field situations. Cite references relating to any similar work undertaken in the past. PROPOSED METHOD Measuring diet preferences of free-ranging possums is fraught with problems. Consequently, we recommend that the palatability of threatened species be assessed through feeding trials with captive possums. These should be individually caged and allowed to adjust to captivity for 2-3 weeks. The threatened species should then be presented together with other common species of known palatability. Relative preference for these species should be scored based on the dry weight of plant material consumed. Diet preference is not the only factor affecting food choice in the field. Consequently, the results of captive preference trials of this type should be.interpreted with considerable caution. RECOMMENDATION We recommend that a small trial be undertaken as a preliminary validation of the method. This should be done using several common plant species for which relative palatabilities are already known from field observations.