Long-tailed bat found in Fiordland believed to be NZ's oldest

A long-tailed bat / pekapeka-tou-roa found in a trap in Fiordland last month has been crowned New Zealand's oldest.

The pint-sized mammal known as T7787 was caught in a harp trap set up during the summer as part of a monitoring programme by the Department of Conservation (DOC).

The long-tailed bat – also known as a long-tailed wattled bat – was given a quick health check before being released back to her colony at Walker Creek in the Eglinton Valley, DOC said today in a media release.

DOC principal scientist Colin O’Donnell, who leads the bat monitoring work, said T7787 is officially the oldest known long-tailed bat in Aotearoa.

"I first caught her when she was a young mother in 2000 and again this month, making her at least 26 years old but possibly as old as 28," O'Donnell said.

He said while T7787 is "going a little grey", she "appears in good health, although signs are she’s stopped breeding".

"We don’t know how long our bats live for so it’s exciting to get this record and know they can live for up to 26 years if conditions are right."

T7787, who weighs just 10.5g – roughly the same as a AAA battery – has produced a pup every year for 20 years since she began breeding at two years old.

The previous record-holder for New Zealand's oldest long-tailed bat was another female, A78806, who was 25. She was last recorded and seen in the Walker colony in 2015.

Once a common sight in New Zealand in the 1800s, the long-tailed bat population numbers have declined dramatically due to habitat loss and predation by introduced pests.

Population numbers for the long-tailed bat – one of two surviving bat species endemic to New Zealand – has been classified by DOC as nationally critical.

But O'Donnell said the bat's long breeding life – and DOC's multi-pronged approach to predator management – bodes well for their recovery and potential to increase towards pre-human population levels.

Long-term monitoring of both long-tailed and short-tailed bats in the Eglinton Valley has shown a steady increase in population numbers in response to large-scale predator control using traps, bait stations, and aerial 1080 to target rats, stoats, and possums.

Prior to 2000, the long-tailed bat population was declining by 5% per year. It has since reversed, with population numbers now growing by 5%.

Bat monitoring is labour-intensive, with teams of volunteers working alongside DOC experts to find bat roosts and set harp traps over six weeks each summer. The teams then return to process the bats' weight and height, before releasing them back to their colonies.

Most of the 1400 bat species around the world live between six and 20 years on average, although a small number are known to live more than 30 years.