Regenerating kamahi, Rakiura Track, Rakiura. Photo - B Maryns

Mouse hunt begins on Rakiura

Images identifying possible mice have prompted Environment Southland to start a search for the small rodents on Rakiura/Stewart Island.

It is believed that Rakiura/Stewart Island does not have an established population of mice, however pictures of small rodents were captured by Predator Free Rakiura during a camera surveillance operation targeting hedgehogs in 2023. Experts could not determine whether the rodents were small rats or mice.

Environment Southland biosecurity and biodiversity manager Ali Meade said that’s why Environment Southland was launching a mouse hunt on the island.

“One of the aims of the Southland Regional Pest Management Plan is to prevent mice from establishing on Rakiura. If our investigations conclude that mice are present on the island, they will put additional pressure on the native ecosystem,” Ali Meade said.

Contractors will set up bait stations, traps, and cameras at eight sites on Rakiura/Stewart Island in areas where the images of small rodents were captured. The sites will be monitored by the contractors for about 10-14 days before they are removed.

“Once we have completed the surveillance of the eight sites, any images and rodents trapped will be analysed, and Environment Southland staff will compile a report on the operation. That report will detail any recommended next steps, depending on whether mice are detected,” Ali Meade said.

Rodents, including mice, can have devastating impacts on New Zealand’s ecosystem and taonga species.

Mice can form huge populations quickly, and have been known to eat bird chicks, especially those in ground nests. They compete with native birds by eating many of the same foods like seeds and invertebrates. When mice eat seeds they destroy them, whereas when birds eat fruits and seeds, the seeds usually survive through the digestive tract and are dispersed as a natural way for native trees to colonise new areas.

It is also important to understand whether there may be a ‘hidden population’ of mice on Rakiura given Predator Free Rakiura’s plans to eradicate rats, feral cats, possums, and hedgehogs. If rats are eradicated from Rakiura/Stewart Island, it could create the ideal environment for a mouse population to increase.

Environment Southland’s mouse investigation is also supported by the Department of Conservation.

“We’re very grateful to the DOC Rakiura Team for their support and assistance in gaining land access for our investigation, as well as planning and logistics support,” Ali Meade said.

Check out a quick Q+A on this project here.

Learn More
  • Snares Snipe on Whenua Hou Jake Osborne v2

    Kaitiakitanga - caring for Tut...

  • Oban, Stewart Island. Photo - DOC V ZINTZEN

    Mouse eDNA research starts on ...