Believed to be the first of its kind in New Zealand, the Doc-designed gate was installed across the Waitutu River, in southeast Fiordland, in September.
Initial testing revealed there were 40 unsuccessful attempts by possums to get across the river, but the gate's design was altered after two possums made it across the bridge, Doc ranger Colin Bishop said.
Further testing showed the modifications were successful, with stoats and rats also deterred by the aluminium gates, Mr Bishop said.
"I am confident that this gate is possum proof."
Funding of $14,000 to build, test and install three more gates is sought, before a planned 1080 aerial drop for the Waitutu Forest begins in late winter, he said.
"We're looking at all alternatives to possum control and this is one of them," Mr Bishop said.
