A population of native bats are in danger of being wiped out by a plague of rats.
Experts are warning a record number of rats could have a “dire” effect on the population of bats in Pelorus.
Forest & Bird top of the south regional manager Debs Martin says they are tracking the highest number of rats ever recorded.
“It’s pretty gruesome out there,” she says.
“We could seriously lose our populations of bats at Pelorus through this mast year.
A mast season is where plants produce an abundance of fruit and seeds.
Deb says rats climb the trees the bats live in, corner them in their holes and eat them.
“The bats can’t get out.
During a previous mast year in Fiordland, bat colonies went locally extinct.
“They thought they had it covered, but they lost one of the colonies,” she says.
“It’s a real gnarly problem.”
Tracking this year has already seen the rats top 60 per cent of traps set.
“We’re tracking double what would be local extinctions,” she says.
Previously, the record high was 42 per cent in 2014.
“We had a really mild summer with a lot of really nice weather, and it was really warm.
“That triggered a whole lot of trees flowering and fruiting.
“We had a huge abundance of fruit and seeds, which is really good for our native birds because they breed up and have a really good year.
“But it’s like putting feed out for the rats,” Deb says.
The group uses tracking tunnels to get an indication of how many rats are in the area.
Debs says, in an ideal scenario, rats would be below five per cent.
“At around 30 per cent tracking, you’ll get some localised extinctions of some species.
“I was walking around Pelorus, and even the walking tracks would be covered in berries and fruit.
“That drives up the number of rats and mice.”
“Normally, when you go into winter rats will run out of food and their population numbers start crashing”.
Deb says rats stash the seed in dry hollows and rat nests and feed on it right through winter.
“Rather than starving through weeding and slowing down, they’re breeding up right through winter.
Debs says the only thing they know that will bring rat numbers down enough is aerial 1080
“Our area is not targeted for aerial 1080 so we’re just going to have to do as much as we can to try and suppress the numbers and take as many out as we can.
“Hopefully we can take a bit of the heat off it, enough to get our bats through.
For further information or to volunteer contact Forest & Bird at forestandbird.org.nz/volunteer.