Pest Control
Pest control began on the property shortly after purchase in 2010. A resident pack of goats was culled mid 2010 followed with the placement of 6 Timms possum traps around the top of the hill and along the road. From 2012, 35 rat traps, 11 stoat traps, 6 automatic possum traps and numerous rat bait stations have been installed to help reduce pest numbers on the site. Funding has been obtained from Waikato Regional Council for pest control and $3335 was awarded to Ohiwai Forest Farm to start intensive control in the 8Ha valley above Boom Stream. Funds will purchase automatic rat, stoat and possum traps which use high pressure CO2 powered ram to kill the pests. Traps reset after each kill and can operate 12 to 24 times before needing replacement CO2 cartridges. Use of automatic traps enables the property to be intensively trapped while saving on labour costs and time.
FERAL GOATS
New Zealand’s native plants are particularly vulnerable to damage from browsing. Herding browsers such as goats cause two-fold damage by eating native plants and by trampling large areas of vegetation and compactable soils.
Goats will eat the foliage of most trees and plants and quickly destroy all vegetation within their reach, eating seedlings, saplings and litter-fall off the forest floor. They do however have strong preferences and will eat out favoured species first such as broadleaf/pāpāuma (Griselinia littoralis) and māhoe (Melicytus ramiflorus) before moving on to less desirable plants. Goats will also strip bark off trees and by eating young seedlings they effectively put a stop to forest regeneration.
RATS
Ship and Norway rats and kiore have a major impact in New Zealand because they are omnivores – eating birds, seeds, snails, lizards, fruit, weta, eggs, chicks, larvae and flowers. The varied diet of rats also makes them competitors with native wildlife for food sources.
Ship rats are found in many different habitats around New Zealand and are widespread in lowland podocarp-broadleaf forests. They are good climbers, so they can access many bird nests high in trees.
On offshore islands, Norway rats are large enough to kill burrow-nesting adult seabirds and eat their eggs and chicks.
Along with other prey, kiore have a significant impact on large flightless invertebrates living on the ground, such as our land snails or weta laying their eggs.
POSSUMS
Possums have a significant impact on many of New Zealand’s natural ecosystems. They occur in high numbers and their own predators, such as feral cats, do not have much effect on controlling possum population size.
Leaves are the main part of their diet, but possums are opportunistic omnivores. They eat buds, flowers, fruit/berries and nectar, which means they compete with native birds and reptiles for food sources. The growth and life-cycle of a tree or plant is significantly affected when all parts of it are eaten. Possums also have ‘favourites’ such as rātā or kamahi trees, leading to an even greater impact on these species.
In 1993, possums were filmed eating the eggs and chicks of kōkako and this evidence changed many people’s views of their threat to wildlife. They eat invertebrates, including weta, and are significant predators of New Zealand land snails such as Powelliphanta. They often occupy holes in tree trunks for their nests which would otherwise be used by nesting birds such as kākāriki and saddlebacks.
Dairy and deer farmers have the added worry of possums spreading bovine tuberculosis. The value of economic loss in primary production for damage and control of possums is in the tens of millions.
STOATS
The effect of stoat predation on the survival of many of New Zealand’s bird species cannot be underestimated. They are voracious and relentless hunters, described as having only two reasons for living – to eat and to reproduce.
Stoats are known to be having a significant effect on birds species such as wrybills, the New Zealand dotterel, black-fronted terns and young kiwi. Birds that nest in holes in tree trunks such as mohua, kākā and yellow-crowned kākāriki are easy prey for stoats who can take out eggs, chicks and incubating adults in one attack.
Stoats are implicated in the extinction of South Island subspecies of bush wren, laughing owl and New Zealand thrush. Even a 3 kg takahe or 2 kg kakapo can be killed by a stoat, that also has a strategy of killing everything in sight and storing the surplus for later.
Stoats and rats are part of a complex predator-prey relationship associated with beech tree seed production. In a periodic ‘mast event’ of beech trees – where high levels of seed production occurs – stoat populations explode assisted by the increased food supply. Later, when the seed supplies run out, the higher numbers of predators have an even greater effect on populations of birds, weta, bats and landsnails.
FERRETS
Ferrets are mustelids, like stoats and weasels. They are bigger than stoats and weasels and are about the same size as a small cat.
The ferrets in New Zealand are ferret-polecat hybrids. Tame ferrets were bred with polecats during the voyage to New Zealand so that they would be better at surviving in the wild. Unfortunately it worked! Now New Zealand has the world’s largest population of wild ferret-polecat hybrids!
The first 5 ferrets were brought to New Zealand in 1879 to get rid of rabbits. Rabbits are their favourite food. From 1882-1883 there were 32 shipments of ferrets from London to New Zealand with about 700 ferrets released. From 1884-1886 another 4000 ferrets and ferret-polecat hybrids were released in New Zealand.
This was bad news for rabbits. It was also very bad news for our native ground-nesting birds. Ferrets eat eggs and chicks and can even kill adult kiwi. They kill albatross chicks, yellow-eyed penguins and little blue penguins. Birds like black stilts and dotterels which live where there are lots of rabbits are especially at risk from ferrets. Ferrets also eat lots of possums, rats and mice. They’re at the top of the predator food chain.
FERAL CATS
Wild or feral cats are a major threat to New Zealands native fauna, and they carry toxoplasmosis which spreads to and causes abortions in sheep.
Cats prey on birds, eggs, weta and skinks, and rats and mice. They will also take rabbits and carrion.
WILD PIGS
Wild pigs are bulldozers of pasture and bush digging around trees, including kauri, disrupting seedling growth and uprooting small trees.
Feral pigs are omnivorous, eating a wide variety of food including grasses, roots, seeds and other plant material as well as carrion, earthworms and insects.