The “Common Brushtail Possum” (Trichosurus vulpecula, named from the Greek for “furry tailed” and the Latin for “little fox”) is a nocturnal, semi-arboreal marsupial, and the largest of the possums.
The possum was introduced to NZ from Australia in the 1800’s (twice, as the first establishment was unsuccessful!) to establish a fur trade. Possums rapidly reached pest status due to abundent food sources and temperate climate that New Zealand offered.
There are a variety of methods available to eradicate the brushtailed possum from the Otago peninsula. If a possum control programme is eventually undertaken, the methods used will be determined by the views and concerns of residents and the recommendations of an experienced pest operator.
At this early stage, the background material in this document will summarise the different control methods that have been used for possum control in New Zealand. These different methods are described in the document only as possible choices for the Otago Peninsula, if the community decides to pursue such a project.
Possums – Why they are a threat:
Actual possum numbers in New Zealand are not known, but estimates put them in the range of 40 to 70 million, with the pests devouring an estimated 7 million tonnes of vegetation a year. In addition, possums carry bovine tuberculosis and spread this contagious disease around cattle and deer herds. It has been estimated that if bovine Tb is not controlled it could cost the country up to $5 billion over 10 years.
As well as possums, stoats, ferrets and rats have flourished in the favourable conditions in this country. They have no natural predators and have caused a great deal of damage to native animals and birds and to the forest environment generally. Stoats were introduced to New Zealand in an attempt to control rabbits, but they soon discovered a far easier meal could be found in the nests of native birds.
New Zealand is unique in having no native ground-dwelling mammalian carnivores, the only native mammals being two species of bat (the short and long tailed). Birds such as kiwi, weka, and takahe have evolved here with little fear of attack and have adapted to living permanently on the ground. This left them vulnerable when possums, stoats and other invaders entered the forests.
Possums are a threat to New Zealand’s environment on two fronts. They eat the eggs of native birds and attack their young; and they destroy significant numbers of native trees. Possums have a preference for trees such as broadleaf, fuchsia, mahoe, pate and three finger. Defoliation through possum damage kills trees slowly but surely. In the most serious cases, possums have caused the complete collapse of the forest canopy in an area within 15-20 years of their arrival. The predation of bird eggs and chicks and has led them to be referred to as “reluctant folivores” in that they eat foliage to survive but prefer other foods.
Possums also compete with birds for food. In preference to leaves, they tend to eat flowers, leaf buds, fruit and insects – all of which are critical for healthy bird populations. In addition, possums are known to raid bird nests and eat eggs and chicks. Terrestrial invertebrates (animals without a backbone, such as insects) are also under threat from possums and other predators, both through direct predation and through competition for their food sources (flowers, fruits and leaves).