A Subtropical Paradise

Lord Howe is a small crescent shaped volcanic island in the north Tasman Sea 600km east of Port Macquarie in New South Wales. There are 28 islands in the archipelago, including Ball's Pyramid, the world's tallest sea stack.

The island is home to around 350 residents and no more than 400 visitors at any time. It is just 10km long and 14.6 sq.km. The west coast is a reef lagoon filled with the world's most southern true corals and the east coast is a necklace of white sandy beaches between rocky headlands.

The northern end of the island has high hills with sheer cliffs plunging to the sea. The southern end has two volcanic peaks, Mt Gower, the highest at 875m and Mt Lidgbird, named for Rear Admiral Henry Lidgbird Ball who discovered the island in February 1788. He named the island after Earl Howe, the First Lord of the Admiralty. The settlement area occupies the centre of the island.

Predator Eradication Project

Island Size
​​Small
14.6 sq.km
Target Predators
Black rats
​Mice
Eradication Methods
​Aerial poison
​Ground baiting
Project Stage
Pre-eradication
​Visited
​August 2018

Lord Howe Island Image Gallery

Click on an image to see a larger view with caption.
​Read more about predator eradication on Lord Howe Island below.

Eradicating Rodents

The Plan

To attempt the eradication of black rats and mice from Lord Howe Island, it is planned to aerially distribute cereal based brodifacoum rodent poison across the island using helicopters. Within the 210ha settlement area 21,000 bait stations will be laid out on a 10m x 10m grid pattern.

The aerial distribution of poison will be in two phases, with an initial distribution at a rate of 12kg/ha. This will be followed by a second distribution at a rate of 8kg/ha, around two weeks later.

​Ground baiting in the bait stations will be carried out until no further sign of rodent activity is recorded. The populations of threatened Lord Howe woodhen and currawong will be captured and held in aviaries for their protection while the poison remains on the ground.
​
The Risks

The project has a range of risks, including:
  • the poison fails to eradicate both rats and mice, although it will certainly significantly reduce numbers
  • the project eradicates rats but fails to eradicate mice that are known to have developed some brodificoum resistance
  • the eradication heavily impacts rare and threatened species, such as woodhen or currawong, potentially causing a genetic bottleneck for these vulnerable populations
  • the project is successful but a rodent reintroduction occurs
The Gains

If rodents can be eradicated, forest birds, native lizards and large invertebrates will all recover.

Masked owls and barn owls that were introduced to control rats will then be able to be removed. Even the forest will benefit from greater seedling regeneration.

​Ultimately, species translocations from Norfolk Island will help restore some of the biodiversity that was driven to extinction by the rodents and other introduced mammals.

A Unique Natural History

Today the Lord Howe Island Group is a UNESCO World Heritage Site. It was listed in 1982 for "its unique landforms and biota, its diverse and largely intact ecosystems, natural beauty, and habitats for threatened species".

Lord Howe Island is probably best known for its kentia palms, an endemic genus that has underpinned the island's economy. These palms form extensive forests that cover much of the lowlands giving the island its subtropical feel.

The islands have been home to a range of endemic fauna, including the world's largest stick insect, but many of its unique animals are now extinct, except for the endangered Lord Howe woodhen, the vulnerable Lord Howe currawong, and Lord Howe silvereye and the Lord Howe golden whistler. There is also the native large forest bat, the Lord Howe Island skink and the Lord Howe Island gecko.

150 Years Of Mammals

Mammal introductions have caused a large number of extinctions on Lord Howe Island. Mice arrived in 1860 and black rats established in 1918, when the SS Makambo was wrecked. Pigs and goats had been released for food and feral cats also established.

The removal of the larger mammals, by hunting and trapping, saw the numbers of nesting seabirds explode, including the Providence petrel that largely only nests on Lord Howe Island. Petrels, shearwaters, terns, noddy's and booby's return each year from across the vast Pacific Ocean to nest on beaches, cliffs and islands.

The plan to use an aerial distribution of poison bait to remove the rodents is due to be carried out during 2019, with the hope a successful eradication will do for terrestrial flora and fauna what the other mammal eradications have done for the island's pelagic fauna.

Postscript

The operation to eradicate rodents from Lord Howe Island commenced in June 2019 when aerial sowing of toxic pellets was carried out and baiting across the bait station network began. The bait station network remained active until November.

It had been estimated that the island supported 150,000 black rats and 210,000 mice before the control operation. A two year monitoring period has now begun during which it is hoped that no rodents will be found before the island can be declared rodent free.

The captive currawong were released once poison baits were no longer on the ground and woodhen were released once the bait stations had been removed. Monitoring also suggests that non-target wildlife poisoning fatalities have also been lower than anticipated.