Conservationists celebrate rare moment of zero possums in Wainuiomata

A recent possum control operation in the Wainuiomata/Orongorongo Water Collection Area was so successful it momentarily knocked the possum population down to zero – the lowest result recorded in the area for 20 years.

Greater Wellington carries out aerial 1080 operations in the water collection area every five years to protect water quality and health of the forest.

Greater Wellington director of delivery Jack Mace says the 0% possum detection by wax tag monitoring is a new record; the previous lowest was 0.1% recorded after a 1080 operation in 2005.  

“It’s very rare that we achieve almost complete elimination like this in a 1080 operation – it was well planned and executed by our Pest Animals team,” Mace says.

“We know results like this never last forever – reinvasion is inevitable – but what we can do is keep knocking possums and rats down to give the forest and birds a break.

“1080 is a safe and effective tool to manage introduced predators, and there were no traces of 1080 recorded in water samples taken from waterways in the area.”

Greater Wellington now has more pest animal data than previous operations thanks to trail cameras which have been installed as part of the council’s new zero ungulate programme, which shows the operation also reduced the numbers of stoats and feral cats.

Mace says that while possum, feral cat and stoat populations are regularly controlled using 1080 and trapping, the council is concerned about increasing deer, goat and pig populations which have “cleared out” the forest ground cover and understory.

“The canopy is relatively healthy; however a forest ecosystem needs all levels – ground cover, understory and canopy – to thrive. The zero ungulate programme will see a significant increase in pest animal control and an extension of the ungulate-proof fence to prevent reinvasion,” adds Mace.

“The aim of the project is to remove ungulates and keep them out.

“The Wainuiomata Water Collection Area is home to towering northern rātā and rimu trees that were left untouched by logging  – jewels in the crown of lower North Island forest. This area is precious and it's our role to protect it.”