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Research into impact of possums and rats on seed production

1 June 2022

Since 2020 researcher Margaret Dickinson from the University of Waikato has been visiting Maungatauari and Mangakawa regularly to survey large fruited tree species in lowland growth forest with the aim of answering the question “Do rats and possums reduce the reproductive capacity of large-fruited broadleaved species in Waikato hill-country forests?”

The Abstract of her Master’s degree thesis begins: Although brushtail possum (Trichosurus vulpecula) browsing can have conspicuous impacts by killing trees outright, there is also evidence of more insidious threats to regeneration of some species through depression of seed production. It is not known how widespread these more cryptic effects are. The elimination of all introduced mammals except mice (Mus musculus) from Sanctuary Mountain Maungatautari (herein referred to as Maungatautari) fourteen years ago, provided a valuable reference system for gauging the impacts of possums and rats (Rattus spp.) on seed production in very similar forest at Maungakawa where these invasive mammals are common. This study compares phenology, fruit development and seed fall of three large-fruited species in the two forests: tawa (Beilschmiedia tawa) and mangeao (Litsea calicaris) are dominant canopy trees, and pigeonwood (Hedycarya arborea, porokaiwhiri) is an important subcanopy species.