Predator Free Dunedin project manager Kimberley Collins said a year earlier a thermal drone detected 58 of the marsupials in the reserve, which had prompted conservationists to increase their efforts in the rugged landscape.
Finding no possums in last week’s follow-up flight was cause for a "cautious celebration", Ms Collins said yesterday.
"Sandymount has always been a difficult location to remove possums from," Ms Collins said.
"There’s quite thick ground cover, which means there’s lots of places for possums to hide — and there’s also a lot of native bush like kānuka and broadleaf species, and that gives the possums quite a lot of food."
The rugged landscape made it really difficult to "actually get in there and do any trapping and monitoring".
For a long time, people had been trying to clear the peninsula of pests.
The Otago Peninsula Biodiversity Group had done some "amazing work over the years", contributing more than 100,000 volunteer hours, to get the area to the point where now more sophisticated methods were required.
But Sandymount, for a variety of reasons, was a stronghold; last year’s count of 58 possums was a conservative estimate, Ms Collins said.
Importantly, though, the first flight showed the reserve was a problem area.
As a result a "toxin operation" was launched at Sandymount as well as the nearby reserves of Boulder Beach and Sandfly Bay.
Working together as Predator Free Dunedin the Halo Project, City Sanctuary and the Otago Peninsula Biodiversity Group were joined in July by the Banks Peninsula Conservation Trust, who lent their expertise with elimination operations, and bait stations containing brodifacoum were deployed.
When they were checked a "good amount of bait" had been taken and crews were hopeful of a good result.
A drone flight was commissioned to see how successful the toxin operation had been.
And despite the positive result further work was needed to make sure no possums had been missed.
"It’s about innovation and research and being crafty and clever and the drone is just one example of this.
"We’ve also got possum dogs that are going out and they’re covering thousands of hectares every couple of weeks ...
"And if they find some scat, that means the team can actually focus their efforts a lot more closely on areas where they know that there’s been recent possum activity.
"The dogs are also really good in places where we’ve struggled to get individual animals because it means that we can actually find areas where the scent is stronger — the dogs are incredible."
The public too had an important role at this stage, Ms Collins said.
She urged anyone who saw a possum — dead or alive — to report the sighting as soon as possible.
The Otago Peninsula Biodiversity Group had now shifted its efforts away from possum work to focus on rodents, rabbits and mustelids, handing the ongoing Possum Free Peninsula operations to Predator Free Dunedin, Ms Collins said.
"The efforts of [Otago Peninsula Biodiversity Group] OPBG’s staff, trustees, and volunteers over the past 15 years have meant the restoration of an iconic landscape that will allow native flora and fauna to thrive for generations to come."
■reportapossum.nz.
