A rat caught on camera on Motutapu Island was tracked using an AI-powered thermal camera (inset). Photo / DOC
A rat caught on camera on Motutapu Island was tracked using an AI-powered thermal camera (inset). Photo / DOC
An elusive Norway rat which was running amok on Motutapu Island in the Hauraki Gulf has been tracked and eliminated with the help of AI technology.
The rat came to light in April this year when it was caught on camera on the island, which had been pest-free since 2011 following an extensive eradication programme.
The Department of Conservation (DoC), with support from Ngāi Tai Ki Tāmaki and Auckland Council, set out a network of 50 cameras to monitor the rodent’s movements and gather data on its favoured routes, locations and direction of travel.
A thermal image of a Norway rat identified on Motutapu Island in July 2024. Photo / DoC
An extra tool in the armoury was the addition of new machine-learning (AI) technology cameras, called “DOC AI CAM”, that tracked, identified and sent real-time alerts regarding the rat to the eradication team.
“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,” said DoC island biosecurity adviser Claire Warren.
“The cameras revealed the rat travelled from a suspected nest site to McKenzie Bay on Rangitoto Island, around 5.8km away, which is much further than we ever expected. 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.”
The new cameras, which utilise thermal imaging, were developed by the Cacophany Project with investment from Predator Free 2050 and DoC’s Tools to Market.
Ngāi Tai Ki Tāmaki Trust's Royal Gurnick setting up a DoC AI camera on Motutapu Island in the Hauraki Gulf. Photo / DoC
The team used a variety of trap types and lures such as peanut butter, rat bedding and rat recordings, but the rat did not interact with any of these human-made devices.
The rat was filmed stocking up on toxic bait over four days in August, and since August 8 there have been no further sightings on the network of cameras. In early October a DoC rodent detection dog and handler undertook a sweep of the island and detected nothing – giving DoC the confidence to declare the rat dead.
“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,” said Ngāi Tai ki Tāmaki Trust chairman Rewa “Billy” Brown.
The Norway rat was caught on camera on Motutapu Island in May this year. Photo / DoC
“Ngāi Tai ki Tāmaki and DoC continue to be vigilant around biosecurity risks on Te Motutapu a Taikehu and Peretū/Rangitoto, as we manage a number of endangered species that will only thrive if we give them a safe space to live,” he said.
The eradication is a big relief as the island is a key recovery site for one of New Zealand’s rarest birds, the tūturuatu/shore plover, with just 250 individuals remaining nationwide. A single rat could have devastated the small island population.
“With every incursion we have, we learn more about how to track and kill mammalian pests,” Warren added. “When they evade all your attempts to entice them into a trap, it forces you to think laterally and innovate.”
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