Lord Howe’s epic conservation battle
A massive pest eradication program will pave the way for the return of a long lost species to its island home.
AG READERS will be familiar with the extinction tale of the Lord Howe Island stick insect and its miraculous 2001 rediscovery atop Balls Pyramid, a 551m-high rocky sea stack 23km south-east of the remote Pacific island (see AG 88 and 129).
Last October, researchers in Australia and Japan published a study in the journal Current Biology confirming the DNA of stick insects from the sea stack matches that of museum collection specimens historically collected on Lord Howe. This confirmed what was already suspected: the insect never went extinct. It’s also paved the way for an exciting plan to reintroduce the species to Lord Howe.
Captive-breeding has been underway since shortly after the insect’s rediscovery and resultant ‘insurance’ populations are held in: Melbourne by Zoos Victoria; an enclosure on the island by the Lord Howe Island Board (LHIB); and in Canada and the UK. But a Lord Howe reintroduction would see the unusual-looking black insects returned to their natural environment and free to recolonise the entire island.
A significant hurdle remains, however: the removal from Lord Howe of two introduced pests that drove the insect to near-extinction on the island in the first place. One is the black rat, introduced in 1918 when SS Makambo ran aground on the island, and the other is the house mouse.To this end a massive – and controversial – eradication effort that will see 42 tonnes of poisoned cereal dropped across the island is planned for this winter.
As well as being held responsible for the demise of the stick insect, rats are believed to have led to the extinction of five bird species and 13 other invertebrates on the island. Getting rid of the rodents will not only allow the stick insect’s return, but also protect another 70 species they threaten, including birds such as the Kermadec petrel, masked booby and white-bellied storm petrel.
Both Australia and New Zealand have attempted massive pest eradication attempts on islands before. In 2014, for example, Australia’s 12,800ha subantarctic Macquarie Island became the largest island to ever be cleared of pests, while NZ has been involved in clearing about 200 of the 1000 or so islands globally subjected to eradication efforts.
But such efforts have rarely been attempted on permanently populated islands, housing tourists, children and pet dogs. Lord Howe is the largest inhabited island where an eradication has been attempted. Despite the hurdles, the LHIB voted late last year to proceed with the $9.5 million eradication after a public vote saw more than half the island’s 300 residents agree to the plan.
Precise dates, which will be around June–July, are yet to be confirmed, although it’s known the poison will be dropped in two instalments, several weeks apart.There’s a risk non-target native species will ingest baits, and an ambitious round-up is planned of two rare, endemic birds – the Lord Howe woodhen and Lord Howe currawong.
With the help of birdkeepers and conservationists from Taronga
Zoo in Sydney, 200 woodhens and
100 currawongs will be caught and cared for in aviaries during the baiting. Taronga staff completed a trial run with a much smaller number of birds in 2013, which went off without any hitches. And similar efforts have been used before to successfully protect
NZ’s weka, a flightless relative of the woodhen.
With any luck, the eradication will be a big success and, later this year, scientists and the LHIB will be able to start thinking about returning the marvellously weird stick insects – or tree lobsters, as they are popularly known – back to their natural habitat.
I’ve seen them in captivity on the island and I’m very much looking forward to going back one day and spotting one in the wild!
Looking weird and waxy, adult Lord Howe Island stick insects can grow to a length of 15cm.