As the number of mice on the mainland grows, Lord Howe Island celebrates the alleged extermination of the hundreds of thousands of rodents that have plagued the idyllic island since the late 19th century.
A long-planned $ 15.5 million bait program was conducted from June to October 2019. It has been 15 months since a rodent was discovered on the island.
NSW Environment Secretary Matt Kean, who visited the island last week, said he was delighted with the success of the program.
“This is an exceptional example of community efforts supported by the world’s leading scientists,” said Kean.
“Wild pests and weeds have wreaked havoc here in the past. This program is reversing that and changing the fate of the plants and animals that call this precious and unique part of Australia home.”
The chief scientist of the Ministry of Planning, Industry and the Environment, Dr. Terry O’Dwyer, has been involved in the amortization program since 2016.
Dr. O’Dwyer said the impact rodents had on Lord Howe Island’s environment was marked from the start.
“There were five species of birds that went extinct shortly after the rats were introduced in 1918, and probably immeasurable invertebrate extinctions, but no one monitored them,” said Dr. O’Dwyer.
“They also had a huge impact on vegetation because they eat seeds and saplings.
“In some places in the forest you would find that there was no regrowth, just old trees, as nothing would replace the aged forest.”
The island was estimated to have up to 300,000 rodents at one time, but despite the environmental impact, an eradication program was a point of contention in the community for many years.
A poll, known on the island as the “referendum”, took place in 2015. 52 percent of those surveyed voted for an amortization program.
“People were concerned that the bait program might kill non-targeted species,” said Dr. O’Dwyer.
“But we did a lot of background research and identified species that are at risk of secondary toxins or that eat the bait directly.”
Dr. O’Dwyer said the endangered Lord Howe Woodhen and Lord Howe Currawong were identified as endangered species during the bait program and as a result have been permanently captured.
“They were kept in specially built enclosures and looked after by employees of the Taronga Zoo on the island,” said Dr. O’Dwyer.
“They were released when it was found safe after monitoring the bait degradation.”
Bait stations were set up around the island’s settlement area and in paddocks with livestock bait to ensure that other species were not affected while uninhabited parts of the island were baited from the air.
“The team that coordinated this did a great job. The bait stations had to be refilled on a constant cycle for up to 10 days each week,” said Dr. O’Dwyer.
“There were 23,000 bait stations that had to be constantly cleaned and refilled.”
Record Woodhen poll
The result has paid off – a recent survey of over 440 grouse, twice as many as 12 months ago and well below the previous record of 250 birds.
Dr. O’Dwyer said they will have to wait two years before declaring complete eradication, but the signs are very promising.
Unfortunately it is difficult to repeat the successful program on the mainland as an area is almost impossible to isolate.
“The bait area would be huge and the unintended targets that would eat the bait would be significant. So it’s a lot harder, but New Zealand has big plans,” said Dr. O’Dwyer.