The Department of Conservation completed a pest control operation across Tongariro Forest last week.
The operation, in conjunction with TBfree New Zealand, will protect some of New Zealand’s most endangered species and help prevent the spread of bovine tuberculosis.
Biodiversity Conservation Services Manager Tongariro Bhrent Guy says both agencies want a pest management system which allows the Tongariro Forest kiwi and whio populations to grow rapidly, while minimising the risk of bovine TB spread by possums.
Tongariro Forest is a national kiwi sanctuary for threatened North Island brown kiwi, as well as being one of five national security sites for the threatened whio, or blue duck. Both species are vulnerable to predation, particularly as chicks, and this operation will support the ongoing recovery of these iconic birds.
“We have been using aerial pest control as a tool for a number of years, and our monitoring shows it is very successful in increasing the survival of kiwi chicks and nesting whio by reducing predation pressure from stoats. What is different is the shift to a three yearly cycle from the previous five yearly operations, which based on research, will deliver better outcomes for kiwi and whio”, he says.
The decision to move to a three yearly cycle came after consultation with the community, and is based on the Department’s research in Tongariro Forest since 2005. Under a three yearly cycle, it is intended to use less toxin more often, and less toxin overall across a span of 10 years.
The operation also used the widespread use of bait treated with deer repellent. “Consulting with the community it was apparent to the Department that the deer population in Tongariro Forest was valued by the community.
"Tongariro Forest was initially protected by people whose primary interest was in the recreational values in the forest, and the Department is mindful to continue to support the recreational community as best we can", says Bhrent. “The use of deer repellent is one way we can carry out this important work to protect whio and kiwi, but at the same time minimise impacts for the hunting community.”
Controlling the numbers of rats, stoats and possums in the forest also provides other forest birds the opportunity to enter the spring nesting season without overwhelming numbers of predators being present.
Plants benefit from the lack of browsing pressure too, most importantly the dactylanthus or "pua o te reinga," the 'flower of the underworld’. This unusual underground parasitic plant is threatened by rats and possums browsing its flowers, and Tongariro Forest has a nationally important population due to ongoing pest control.