A dead rat discovered on Ulva Island on January 13 has prompted intensified monitoring efforts on the nature sanctuary, located 780 metres from Stewart Island/Rakiura.

The island, a popular destination for visitors wanting to experience its thriving wildlife, has been predator-free since 1997 and is home to native species such as the Stewart Island brown kiwi (tokoeka), kākā, kākāriki, yellowhead (mohua), and South Island saddleback (tīeke).

Department of Conservation (DOC) Acting Operations Manager for Rakiura, Bridget Carter, confirmed the immediate response following the discovery, with staff checking traps, using lured cameras, and deploying rodent detection dogs to assess the extent of the rat presence.

“Since the dead rat was found, trail cameras have captured further rat activity,” said Carter.

“Ongoing monitoring will help us determine if this is an isolated case or if there are more rats on the island.”

DOC’s strategy includes continuing surveillance and trapping efforts, with toxin use considered in areas where rats are present but avoid traps.

Despite the discovery, Carter emphasized that the situation shows the biosecurity monitoring system is functioning as it should.

Rats typically manage to reach Ulva Island one or two times a year, largely due to its proximity to Rakiura, where rats are present.

The risk of incursions increases when rat numbers are high on the mainland, especially in warmer weather.

Visitors are asked to report any rat sightings on the island by taking photos, noting the location, and informing the DOC Rakiura Office.

In 2023, DOC carried out a successful rat eradication operation after a breeding population was found on the island. Ulva Island was declared rat-free in early 2024.

However, a single rat caught in February 2024 was genetically confirmed to be unrelated to the 2023 population, with intensive monitoring showing the island was again free of rodents.

With the ongoing threat of rat incursions, DOC’s biosecurity systems will continue to monitor and respond rapidly to protect Ulva Island’s predator-free status.