The hunt is on for mice on Rakiura/Stewart Island after possible trail camera image of the small rodent were recorded by last year.

The image was from surveillance cameras set, by Predator Free Rakiura/Manaaki Whenua, to track hedgehogs in 2023.

However experts could not determine whether the rodent images were of small rats or mice.

Environment Southland (ES) 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,” Meade said.

Mice can form huge populations quickly and can have devastating impacts on New Zealand’s ecosystem and taonga species.

They have been known to eat bird chicks, especially those in ground nests as well as competing 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. 

ES 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 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,” Meade said.

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, Meade said.

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,” Meade said.