Contribution by possums to seed rain and subsequent seed germination in successional vegetation, Canterbury, New Zealand

The contribution of seeds and fruit to the diet of the introduced brushtail possum (Trichosurus vulpecula) was examined in seral vegetation in lowland Canterbury, New Zealand. Fruit and seeds comprised c. 70% of total possum diet, and possums contributed 17% of the dispersed seed rain for the period of our study. The effect of gut passage on germination was measured for five seed species by germinating seeds recovered from faeces of captive and wild possums. At least one-quarter of seeds of four of the species germinated. Two seed species showed a negative effect, and one a positive effect of gut passage relative to uningested seeds. Although possums may increase the spread of invasive weeds, their seed dispersal behaviour may offer conservation benefits by accelerating succession in seral vegetation. Because of the reduction in numbers of large-gaped native birds (e.g. kereru, Hemiphaga novaeseelandiae), possums may now be the only dispersal agents for large-seeded native species in many areas.