Lord Howe Island sees a wildlife miracle after mass cull of 300,000 invasive rats and mice

Melissa Martin and Luisa Rubbo
Feb 02, 2021, updated Feb 02, 2021

Australia is on tsunami watch after an earthquake of magnitude 7.7 near New Caledonia. Photo: AAP

The Lord Howe Island community is hailing an “ecological renaissance” after a $15 million eradication project appears to have successfully eliminated rodents from the World Heritage-listed island.

In 2019, rodent baits were distributed throughout Lord Howe Island to deal with an infestation of about 300,000 rats and mice that had caused the extinction of some native species.

There hasn’t been a rodent sighted on the World Heritage-listed island in 15 months, and the baiting program has had startling effects on the populations of local wildlife.

Department of Planning, Industry and Environment senior scientist Dr Terry O’Dwyer said the numbers of the endangered flightless Lord Howe woodhen have doubled in 12 months.

“It was a really remarkable result, and one that we didn’t expect,” he said.

The woodhens, which are an endangered species, were isolated at Sydney’s Taronga Zoo during the rat eradication program.Photo: NSW Environment Minister’s Office

Environmental damage done

When the baiting program began, it was estimated that there were around 1000 rodents for each of the island’s 350 residents.

Environment World Heritage for the Lord Howe Island Board manager Hank Bower said they caused the extinction of at least five land birds, 13 invertebrates and two plant species.

“Every night they were going out, eating everything … small land snails, all the invertebrates, all the seeds, chicks, eggs,” he said. “They were just out there, consuming every night.”

Mr Bower said the rodents even compromised the residents’ ability to grow vegetables and fruits.

Before the baiting program began on Lord Howe Island rodents were “consuming every night”. Photo: ABC

Mice first appeared on the island in 1850, and it is thought the rats came in 1918 after escaping from a sinking ship off the coast.

More than a century later, in June 2019, the Lord Howe Island Board, the NSW Environmental Trust and the Commonwealth Government funded the $15.5 million eradication project.

Poison was placed inside 22,000 lockable traps around the island, while in inaccessible areas, pellets were distributed via helicopter.

Woodhens flourish

There were fears the island’s meagre population of endangered woodhens would be at risk of eating the pellets, so they were isolated at Sydney’s Taronga Zoo while the rat eradication program took place.

Once returned, their numbers flourished.

Dr O’Dwyer said the woodhens had numbered as few as 200 individuals.

“But for the latest survey we recorded 460 birds, and the record previously was only 250 individuals,” Dr O’Dwyer said.

“We thought that the rodents would have had some impact on the woodhens through competition for food – they both forage in the leaf litter and also [the rats] would probably eat some eggs and chicks.

“But we didn’t expect [the woodhens] to respond as quickly as they have.”

Currawongs and other birds are increasing in numbers on the island following the eradication program. Photo: ABC

It is not only the woodhens that are flourishing, other species’ numbers are up too, including the black-winged petrel and endemic land snails.

Dr O’Dwyer said many plant species were also emerging after decades of devastation by the rodents, which ate the seeds and seedlings, hampering regeneration.

Environment World Heritage for the Lord Howe Island Board manager Hank Bower said locals had also noticed the insects had returned.

“We’ve been hearing crickets. We’d only hear crickets very rarely, now every night there’s a chime of crickets,” he said.

“The old-timers are saying they’ve never seen that plant fruit or flower; we’re seeing seedlings on the ground that we’ve never seen before.

“It’s an ecological renaissance – it’s just amazing.”

Welcome change

The baiting program initially caused controversy within the small island community, with some concerned the poison could further compromise the pristine ecosystem.

But Mr Bower said everyone now appeared happy with the result.

“The [community] wasn’t happy with the process leading up to it necessarily, but they are happy that the rodents have gone and everyone, I think, is enjoying seeing the island flourish.”

The island will not be declared officially rodent-free until two years after the baiting.

-ABC

Topics: Environment