Koalas feel effects of shrinking gene pool

·2-min read

Two dogs with a nose for koala poo have helped deliver a sobering report on the genetic health of a koala population fractured by the Pacific Highway and urban sprawl.

The news isn't good for the koalas of Port Stephens. Evidence suggests they are suffering the effects of enforced separation and that means they'll be less able to cope with disease and climate change.

Specially-trained detection dogs Taz and Missy completed three missions to sniff out koala scat in 2018, 2019 and 2020.

Researchers then analysed the DNA of the once-connected koala community that is now fragmented by the highway, other roads, habitat loss, houses and buildings.

Koalas living closest to the coast, on the Tilligerry and Tomaree peninsulas, were found to be significantly different from those further west, around Karuah, Ferodale and Balickera.

There was also evidence to show there was only limited gene flow between populations that are very close together.

That was true for population clusters sampled at Balickera and Ferodale, which are less than 10km apart but separated by the Pacific Highway.

WWF Australia, which commissioned the research, says it demonstrates the urgent need to protect existing habitat, regenerate cleared forests and plant tree corridors to reconnect isolated populations.

It also wants more research into koala genetics and better koala infrastructure, including safe highway crossings to boost gene flows between separated clusters.

Olivia Woosnam is a koala conservation ecologist from OWAD Environment and worked on the research with dogs Taz and Missy.

She says koala habitat was largely connected in Port Stephens until the 1940s when tree clearing ramped up due to urbanisation and infrastructure development.

"Now koalas are confined to smaller patches of forest surrounded by inhospitable habitat," Ms Woosnam said.

"Previous research shows isolated populations rapidly become genetically differentiated and lose genetic diversity. This is likely what has happened on the peninsula and appears to be starting to happen inland too."

Meanwhile, the Queensland government has announced several new grants to help koalas, including $100,000 to trial a chlamydia vaccine in 500 koalas in the state's southeast. Chlamydia is a major threat because it causes infertility.

Another grant will see drones used to assess high risk areas for interactions between koalas and wild and domestic dogs.