Source: NZ Department of Conservation
Date: 17 September 2025
The Ettrick Burn Valley in Fiordland is home to one of the only remaining populations of the southern lesser short-tailed bat/pekapeka, with a colony of around 400 bats discovered there in 2018.
Department of Conservation Te Anau Operations Manager John Lucas says a heavy beech mast predicted this summer could have disastrous impacts on the tiny population.
“This summer the beech forests are going to be absolutely bursting with fruit, and all that extra food is going to drive up the numbers of rats in the following months,” says John.
“This is bad news for the pekepeka. 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.”
Southern lesser short-tailed bats are only found in three locations in the South Island – predator free Whenua Hou/Codfish Island, the Eglinton Valley in Fiordland which has regular aerial predator control, and the Ettrick Burn Valley. A population in Kahurangi National Park has not been detected since 2008.
In response, DOC is planning an aerial operation using cereal 1080 bait targeting rats over 5429 ha in the Ettrick Burn area in November or December this year, prior to seeding this summer. A potential second round may be required in early 2027 depending on predator numbers.
John Lucas says the timing of the operation has 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.”
This is the first time aerial predator control will be done in the Murchison Mountains, which are also home to Northern Fiordland tokoeka (kiwi), kea, whio, rock wren/tuke, numerous other native forest birds and the nationally vulnerable takahē. In the past, some takahē have been known to eat 1080 cereal bait so additional measures have been developed as mitigation for this operation.
“The Ettrick Burn Valley, at about 5,429 ha, is a small part of the area’s 50,000-ha takahē habitat and at that time of year, takahē are typically above the bush line and will be out of the planned treatment zone,” says John.
“We’ve taken steps to reduce the risk further – staff will monitor takahē during the operation and may attempt to relocate high-risk birds if they are found within the operational area.”
Consultation with iwi and key groups has taken place and public notification will occur in the coming weeks.
Getting ahead of this summer’s heavy mast is an important step in securing a future for the short-tailed bat, says John.
“Like most of New Zealand’s wildlife, these pekapeka are extremely vulnerable, and once they’re gone, they’re gone for good. We need to get in ahead of the mast and nip rat numbers in the bud, before they become a problem.”
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