Kahurangi National Park Anatoki pest control a boost for native bird populations

Date:  06 April 2010

Native birds, including great spotted kiwi and whio/blue duck, are likely to have had more breeding success in recent months in Kahurangi National Park’s Anatoki River area due to aerial 1080 pest control in October which kept predator numbers low over summer when predator plagues have erupted in many beech forest areas.

Monitoring at the end of February, as part of Department of Conservation research, found rat and stoat numbers remained at very low levels – significantly lower than at a comparison site in the adjoining Waingaro River catchment where no pest control has taken place. At the densities stoats and rats are at in the Waingaro Valley, they are likely to be taking a major toll on native wildlife until their numbers start to drop off over winter.

The Anatoki operation was timed to curb the expected explosion in rat and stoat numbers. The predator plagues were predicted due to a beech mast which created an abundant beech seed food supply for rats over winter increasing their numbers and also swelling stoat numbers with more rodents for them to feed on.

DOC Golden Bay Area Manager John Mason said the aerial 1080 operation over around 11,000 hectares of the Anatoki area was primarily aimed at protecting three species of threatened giant Powelliphanta snails from predation by possums and rats but it also would have benefitted other native wildlife and vegetation.

“One of the benefits of aerial 1080 operations is that they achieve multi-pest control with reductions not only in possums and rats which eat the toxic baits but also, indirectly, stoats through their eating poisoned carcasses.

“We have been monitoring predator numbers following the Anatoki operation as part of wider South Island research aimed at determining how large-scale pest control tools can best be utilised to protect native wildlife from stoat and rat plagues triggered by beech masts.

“Rat and stoat population densities are assessed using lines of tracking tunnels, baited to lure predators into them, and measuring how many show pest footprints on ink pads inside the tunnels.

“In the February monitoring, 2% of the tunnels inside the Anatoki operational area showed evidence of rats. In comparison, in the Waingaro Valley, where no pest control has taken place, 32% of tunnels showed rat sign, around the same level as monitored there in November.

“No stoats were detected inside the Anatoki operational area. Stoat numbers were very high though in the Waingaro area with 66% of tracking tunnel lines showing stoat sign. 

“At the low levels they are at in the Anatoki area, these predators are not likely to be having a noticeable impact on native birds. With fewer possums, rats and stoats to prey on them, more chicks will have fledged and more nesting adults will have survived over the current breeding season.

“Research monitoring at other sites has shown bird breeding has benefitted from predator control over the current breeding season. Yellow crowned parakeets/kakariki have had good nesting success in a Springs Junction area where aerial 1080 pest control has greatly reduced rat and stoat numbers. Mohua/yellowheads have also had good nesting success in The Catlins in South Otago where there has been aerial 1080 rat control and stoat trapping.”

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