In February, the Otago Daily Times published an image of a possible mouse caught on Stewart Island/Rakiura pest monitoring cameras, which sparked concern the rodents may have found their way across Foveaux Strait.
Despite rats and other pests being present on Stewart Island, mice are not known to have established themselves there.
Environment Southland said in a release yesterday it believed the island did 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 was 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," she said.
Contractors will set up bait stations, traps and cameras at eight sites on 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.
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 such as seeds and invertebrates.
It was also important to understand whether there might be a "hidden population" of mice on Rakiura given Predator Free Rakiura’s plans to eradicate rats, feral cats, possums and hedgehogs, Ms Meade said.
If rats are eradicated from Stewart Island, it could create the ideal environment for a mouse population to increase.
