Avon population

Unexpected discovery of native bat DNA in Christchurch

A long-tailed bat prepares to take off.  (File photo)

Davidson-Watts Ecology

A long-tailed bat prepares to take off. (File photo)

Endangered native bats may be living in northern Christchurch, a new study has found.

Evidence of the long-tailed bat​ (pekapeka-tou-roa)​ has been detected in water samples taken from the River Styx catchment using a technique called “environmental DNA” ​(eDNA), similar to looking for evidence of Covid-19 in sewage.

“Detecting bat DNA here in Christchurch is a surprise,” said Professor Jon Harding, a freshwater ecologist at the University of Canterbury involved in the research.

Bethany Baker, conservation projects coordinator at the Pūharakekenui Styx Living Laboratory Trust, who conducted the research, said the long-tailed bat is a ‘species of national importance‘ and was not known to have been in the area.

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The last sightings of bats in Christchurch date from 1885, when they were observed roosting under the wooden bridges crossing the River Avon, according to DOC.

Earlier this year, the trust took water samples from six sites in the Styx watershed.

These were processed and all collected eDNA was compared against a database of unique DNA fingerprints from a multitude of species.

Baker said the Wellington lab technician processing the samples was amazed to find DNA fragments from capybara, a rodent native to South America.

A juvenile long-tailed bat.

Anna Porter/Supplied

A juvenile long-tailed bat.

He was unaware that the Willowbank Wildlife Reserve kept capybara and was upriver from the sampling sites.

The nearest known population of long-tailed bats was at Geraldine. According to the DOC, the bat (Chalinolobus tuberculatus) was brown and weighed between 8 and 11 grams.

eDNA techniques were developed in the late 1990s but were still relatively new to science, Harding said.

They were often used to detect animals that spent their entire lives in water – shedding their skin and scales, defecating and dying there.

Detection of eDNA fragments from land animals – not to mention flying animals – was less common because they only sporadically deposit genetic material in water, blogged Amy Gaultan environmental scientist and community engagement manager at Wilderlab, an eDNA lab in Wellington.

“This means that if you are lucky enough to detect pekapeka-tou-roa eDNA in your sample, it is a cause for celebration,” she wrote.

Davidson-Watts Ecology

New Zealand long-tailed bats

eDNA cannot tell researchers how many individuals were present.

It is possible that the eDNA came from a solitary, possibly transient individual, or even from a bat carcass.

The trust will now search for the bats using electronic loggers capable of picking up their high-frequency echolocation calls. These bats usually roost in tall, old trees. Their calls include a frequency component that can be heard by some humans, according to DOC.

The Pekapeka long-tailed bat won the 2021 Bird of the Year competition.