Role of detoxification of plant secondary compounds on diet breadth in a mammalian herbivore, Trichosurus vulpecula

Theory predicts that mammalian herbivores detoxify different classes of pla nt secondary compounds via separate metabolic pathways and that generalist herbivores maintain broad diet breadth to avoid overloading individual deto xification pathways. We tested the hypothesis that a generalist marsupial h erbivore, the common brushtail possum, Trichosurus vulpecula. can maintain a higher intake of food when allowed to select from two diets containing di fferent profiles of secondary compounds (phenolics and terpenes) than when given access to the diets individually. Diets consisted of a fruit and vege table mash to which was added ground leaves of either Eucalyptus melliodora or E. radiata. E. melliodora and E. radiata differ in their concentrations and types of secondary compounds. Brushtail possums include these eucalypt species as parr of their natural diet. We measured food consumption and de toxification metabolites of possums on these diets. Consistent with the hyp othesis, animals presented with a choice of both diets consumed more food t han animals given diets singly. One of the two indicators of detoxification , acid load in urine, differed significantly between diets while the other, glucuronic acid, did nor. These results provide partial support for the hy pothesis that diet breadth is governed by detoxification abilities.