AI cameras help save Motutapu Island's rare birds

Using AI cameras, a Norway rat has been successfully eradicated from the pest-free island of Motutapu in the Hauraki Gulf.

The Department of Conservation (DOC), with assistance from Ngāi Tai Ki Tāmaki and Auckland Council, engaged in efforts over five months to capture the rodent, which was first detected in late April. The rat's presence was confirmed through surveillance footage showing it consuming bait over a four-day period in August.

Since 8 August, the comprehensive camera network reported no signs of the rat. A recent thorough inspection by a DOC rodent detection dog and handler yielded no detections, leading the department to declare the rat deceased.

Claire Warren, DOC Island Biosecurity Advisor, noted that both conventional and contemporary methods were employed to ascertain the rat's whereabouts and behaviour, which ultimately led to its extermination. Approximately 50 cameras were pivotal in tracking the invasive creature.

"We used a combination of standard trail cameras and AI cameras that gave us important and surprising information about the rat's behaviour, routes and favourite locations," explained Claire Warren.

Evidence from the cameras revealed that the rat had traversed an unexpected distance of 5.8 km from a presumed nest site to McKenzie Bay on Rangitoto Island.

Warren stated, "The camera network helped us conclude that there was only one rat on island, and it was instrumental in determining where to lay toxic baits."

Two thermal imaging cameras, known as DOC AI CAM and created by the Cacophony Project, played a crucial role. "The AI cameras sent us alerts when the rat was seen on camera. This gave us real-time information about the rat's location and direction of travel which really helped us target it," Warren mentioned.

Billy Brown, Chair of Ngāi Tai ki Tāmaki Trust, expressed satisfaction with the outcome: "It is always great to have a successful end to an incursion response, as they can be very challenging and a huge threat to taonga species on these beautiful islands."

Brown added that vigilance continues around biosecurity threats on both Motutapu and Rangitoto given the presence of several endangered species which need a secure environment. "I want to congratulate the DOC and Ngāi Tai ki Tāmaki team on island, along with the myriad of people who run and manage these responses, for embracing kotahitanga, as together we can eliminate these threats faster," Brown stated.

The response team had employed multiple trap types and lures, including peanut butter and rat recordings, without success. This highlighted the difficulties involved in maintaining pest-free areas.

"With every incursion we have, we learn more about how to track and kill mammalian pests. When they evade all your attempts to entice them into a trap, it forces you to think laterally and innovate," Warren said.

The removal of the rat is a relief as the island is a vital recovery site for the tūturuatu or shore plover, one of New Zealand's rarest birds, with only 250 individuals left nationally. A solitary rat could have posed significant danger to the island's ecosystem.

Motutapu serves as nesting ground for various sea and shore birds, which became particularly vulnerable to predators during the nesting season that commenced in July.