The first aerial drop of the controversial poison 1080 into Fiordland's Murchison Mountains, will take place this summer in an attempt to protect one of the last remaining populations of southern lesser short-tailed bat/pekapeka.

Famous as the location of Dr George Orbell's 1948 rediscovered of the flightless takahē, the Murchison Mountains is also home to Northern Fiordland tokoeka (kiwi), kea, whio, rock wren/tuke and - in the Ettrick Burn Valley - around 400 of the rare pekapeka.

Pekapeka are now only found on predator free Whenua Hou/Codfish Island, Fiordland's Eglinton Valley, and the Murchison Mountain's Ettrick Burn Valley.

The Department of Conservation Murchison Mountains operation, in response to an expected plague of predators following this summer's predicted 'mass mast' of beech tree seed, will concentrate within the 5429 ha Ettrick Burn Valley.

DOC Operations Manager John Lucas said the heavy beech mast could have disastrous impacts on the tiny bat population.

"By the following summer the mast will be over, and all those extra predators will turn to the next available food source, our native species."

"These pekapeka are especially vulnerable to rats as they forage for food on the forest floor – an unusual strategy they evolved due to New Zealand’s lack of mammalian predators.” 

Lucas said the timing of the operation had been carefully planned to control rat numbers before they reach high levels.

“We know from our work in the Eglinton Valley that our predator control works extremely well; the short-tailed bat population there has grown from 300 to nearly 4,000 pekapeka over the years."

"What we do now ahead of the mast can really make a difference.”

Lucas said the Ettrick Burn Valley was only a small part of the area’s 50,000-ha takahē habitat, and takahē would - at that time of the year - typically be above the bush line so out of the planned treatment zone.

However Lucas said takahē had in the past been known to eat 1080 cereal bait, so additional measures would be employed - including staff monitoring birds and attempting to relocate any found within the operational area.

Consultation with iwi and key groups had already taken place and public notification will occur in the coming weeks, Lucas said.

The aerial operation in the Ettrick Burn area is expected to take place in November or December this year, prior to seeding this summer, with a potential second round - if predator numbers warrant - in early 2027.