Renewed Hope for the Iconic “Tree Lobster” on Lord Howe Island
A glimmer of hope has emerged for the survival of a unique insect, long believed to be extinct. Two thriving colonies of the Lord Howe Island stick insect, affectionately nicknamed “tree lobster” or “walking sausage,” have been discovered on a remote rock outcrop of Lord Howe Island. This remarkable finding breathes new life into conservation efforts for the critically endangered species.
The insect, scientifically known as Dryococelus australis, has its sole known wild habitat on Ball’s Pyramid. This dramatic, sheer rock islet, forged by volcanic activity over six million years ago, stands as the world’s tallest volcanic stack at a towering 572 metres. Its formidable geography presents significant challenges for access, making surveys difficult and opportunistic.
However, during a recent, brief survey conducted by the NSW Department of Climate Change, Energy, the Environment and Water (DCCEEW), weed officers stumbled upon the insects in two previously unrecorded locations. Craig Stehn, a threatened species officer involved in the discovery, noted the insect’s exceptional ability to evade detection. “This species is very cryptic and hard to detect as they have an incredible ability to hide and camouflage themselves,” Stehn explained.
A Species on the Brink: The “Rarest Invertebrate”
The dedicated officers managed to locate a total of nine adult insects, with seven of them being carefully captured for a vital breeding program. This latest discovery marks a significant milestone, occurring precisely 25 years after the insect was first rediscovered on Ball’s Pyramid.
The Lord Howe Island stick insect’s history is a poignant tale of near-extinction. In times past, these insects were so abundant that early settlers on Lord Howe Island used them as fishing bait. Their fortunes dramatically changed in 1918 when black rats accidentally colonised the island following a shipwreck. For 15 years, the rodents wreaked havoc, and the stick insect was presumed extinct. It wasn’t until 2001 that it was rediscovered, clinging to existence on the remote Ball’s Pyramid.
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The Australian Museum considers Dryococelus australis to be “may be the rarest insect” and potentially the “rarest invertebrate” globally. Rohan Cleave, a phasmid specialist at Melbourne Zoo, echoed this sentiment, describing them as “one of the most rare invertebrates known in the wild.”
Estimating the wild population is a complex task due to the insect’s isolated habitat. However, NSW Environment and Heritage currently lists the wild population as “fewer than 50 mature individuals in the wild.” Cleave also highlighted Australia’s concerning record of invertebrate extinction, which is estimated to be between one and three species per week. Despite this grim statistic, he expressed optimism for the Lord Howe Island stick insect, noting that it benefits from “an incredible international conservation breeding program and captive insurance population.”
A Global Effort: Breeding for Survival
The seven newly discovered insects have been transported over 1,000 kilometres to Melbourne Zoo, a facility that has been at the forefront of the Lord Howe Island stick insect breeding program for the past 23 years. This vital initiative is further supported by esteemed institutions such as San Diego Zoo, Bristol Zoo, Toronto Zoo, and, most recently, Prague Zoo in the Czech Republic.
Cleave described his delight at the arrival of the new specimens, calling them “beautiful and placid animals” that are “you can’t help but fall in love with.” He emphasised their profound importance: “They’re more important than I am, their future is much more important, as I want to see this species survive long into the future.”
Since the Melbourne Zoo program commenced with just two insects in 2003, it has successfully bred an impressive 19 generations. However, the program has faced challenges due to limited genetic diversity stemming from the initial small founding population of only five wild-captured phasmids. “So that’s been really tricky and that’s why any injection of new genetics is vitally important,” Cleave stated. He proudly added, “This is now an international captive breeding program, that is really well-known for what can be done with such a small founding population to start with.”
The success of Melbourne Zoo’s captive breeding efforts for these rare phasmids has garnered international acclaim, even attracting the attention of renowned British naturalist Sir David Attenborough, who visited the breeding project in 2012. The recent arrival of two adult males, three adult females, and two sub-adult females offers renewed hope for the critically endangered species. “It means a more robust species you can potentially return to the wild in the future,” Cleave noted. The Melbourne Zoo population now fluctuates seasonally between 700 and 800 live insects.
In a significant development, Prague Zoo announced on February 25th that it had successfully hatched 13 Czech-bred Dryococelus australis as part of the ongoing international breeding program.
Reintroduction on the Horizon: A Restored Island Ecosystem
With the successful eradication of rats from Lord Howe Island in 2023 – a monumental achievement making it the largest inhabited island globally to achieve this status – plans are now underway to reintroduce the stick insect to its ancestral home. Surveys are being conducted among Lord Howe Island residents to gauge community sentiment and gather vital information.
Suzie Christensen, Chief Executive of the Lord Howe Island Board, stressed the importance of these surveys, acknowledging that “the insect hasn’t been seen here in anyone’s living memory.” She outlined the proposed reintroduction strategy: “Based on the scientific advice, the first place they would be brought back to would be in the remote areas of the permanent park preserve, up in the mountains and that should give them the best chance of success.”
The removal of invasive rats has already spurred a remarkable ecological recovery on the island. “A lot of the land snails and invertebrate species have really rebounded, seabirds are in huge numbers now, so it’s a real sort of renaissance of the biodiversity on the island,” remarked Stehn, underscoring the island’s revitalised ecosystem, which now offers a promising future for the Lord Howe Island stick insect.
