New Method of Possum Control

( An innovative possum proof gate designed by the Department of Conservation will be used as another method of possum control in the Waitutu Forest.

The prototype was installed in September 2009 on a bridge across the Waitutu River and after a successful trial period, funding is being sought to install a further three gates on bridges over the Waitutu and Wairaurahiri rivers.

DOC Ranger Colin Bishop said the Department continued to look into alternative pest control methods and the new gate design was a significant advancement in the Department’s Waitutu Forest possum control operation.

“I am confident that this gate is possum proof,” Mr Bishop said. “As far as I’m aware there is no other gate like this in the country.”

DOC will carry out an aerial 1080 operation in the Waitutu area in late winter and the possum proof gates will help to stop the spread of possums across the rivers.

“We’re looking at all alternatives to possum control and this is one of them.”
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It is estimated the design, building, testing and installation of the three gates on the two, single person bridges, will cost $14,000.

Funding from individuals, businesses and organisations is needed to cover these costs and a sponsorship plaque would be displayed on site. This funding needs to be secured by the end of April, ahead of the aerial 1080 operation in Waitutu Forest.

“It is a great opportunity for the local community members to help with the preservation of the Waitutu Forest,” Mr Bishop said.

The prototype possum control gate was built by Southern Institute of Technology engineering students and made out of aluminium, which because of its flat surface quality, possums are unable to climb up or around it.

Initial testing of the control gate included monitoring with night vision cameras. On one night, there were 40 unsuccessful attempts by possums to get across the bridge. Over three nights of monitoring only two possums got across the bridge so the gate was modified to ensure this did not occur again. Further testing showed the modifications were successful in stopping possums from crossing the bridge and a stoat was also unable to get through or over the gate.

“This is an indication of just how often the bridges are used by possums and although designed to prevent possum access, the testing has showed the gates will also act as a deterrent to stoats and we believe rats as well,” Mr Bishop said.

As each gate is erected, monitoring will be carried out involving on site camp outs, night vision goggles and cameras to watch the possum’s response and ensure that each gate is possum proof.

As the bridges are on the South Coast Track, in Southern Fiordland National Park, the success of the gates will also be reliant on the public, mainly trampers, ensuring the gates, which operate on a swing-hinge, are closed.

The Waitutu and Wairaurahiri rivers are excellent natural barriers to the spread of possums in this area so it is essential the possum proof gates are installed as the gates will increase the effectiveness of the natural river barrier.

Media Release 17 March 2010 from Department of Conservation.