World Heritage-listed Lord Howe Island wildlife thrives after eradicating 300,000 rodents

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The Lord Howe Island community is celebrating an “ecological renaissance” after a successful $ 15 million rodent eradication project to remove rodents from the world heritage island.

Important points:

  • A rodent eradication program began almost 18 months ago on Lord Howe Island
  • The infestation of rats and mice on the island had reached more than 300,000
  • The program is credited with more than doubling the population of the endangered flightless Lord Howe Woodhen

In 2019, rodent baits were distributed on Lord Howe Island to control an infestation of approximately 300,000 rats and mice that led to the extinction of some native species.

Rodents have not been sighted on the world heritage island in 15 months, and the bait program has had a startling impact on local wildlife populations.

The chief scientist of the Ministry of Planning, Industry and the Environment, Dr. Terry O’Dwyer said the number of flightless Lord Howe Woodhen at risk had doubled in 12 months.

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

The endangered forest hens were isolated at Taronga Zoo in Sydney during the rat control program. (Supplied: Office of the NSW Environment Minister)

Environmental damage done

When the bait program began, there were an estimated 1,000 rodents for each of the island’s 350 residents.

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

“Every night they went out and ate everything … small land snails, all invertebrates, all seeds, chicks, eggs,” he said.

“They were just out there consuming every night.”

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

Before the lure program began on Lord Howe Island, rodents consumed “every night” (ABC News: Mridula Amin)

Mice first appeared on the island in 1850, and it is believed that the rats came in 1918 after escaping offshore from a sinking ship.

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

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

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Woodhens thrive

There were fears that the island’s meager population of endangered forest hens might be at risk of eating the pellets, so they were isolated at Sydney Taronga Zoo while the rat eradication program was in progress.

Upon their return, their numbers blossomed.

Dr. O’Dwyer said the Woodhens had been bred in captivity for the past few years and then released and about 200 individuals counted.

“However, the last survey recorded 460 birds, up from 250 people before,” said Dr. O’Dwyer.

“We thought that by competing for food, the rodents would have had some influence on the Woodhens – they forage in both foliage and food [the rats] would probably eat some eggs and chicks.

“But we didn’t expect it [the woodhens] to reply as soon as possible. “

A bird in mid-flight, near a dead tree Currawongs and other birds continue to increase after the island’s eradication program. (ABC News: Mridula Amin)

It’s not just the forest hens that thrive, but numbers of other species as well, including the black-winged petrel and endemic land snails.

Dr. O’Dwyer said many plant species continued to emerge even after decades of devastation by the rodents that ate the seeds and seedlings and hampered regeneration.

The World Heritage Site for Lord Howe Island Board Manager Hank Bower said locals had also noticed the insects had returned.

“We heard crickets. We rarely heard crickets, now there is a chime every night,” he said.

“The old-timers say they have never seen this plant fruit or flower. We see seedlings on the ground that we have never seen before.

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

Welcome change

The bait program initially sparked controversy within the small island community, with some feared the poison could further harm the pristine ecosystem.

But Mr Bower said everyone now seemed pleased with the result.

“The [community] I wasn’t exactly happy with the process that led to this, but they’re glad the rodents are gone and everyone, I think, is enjoying seeing the island flourish. “

The island is not officially declared rodent-free until two years after the bait.