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EN-015 Insect · Lord Howe Island 2001

Lord Howe Stick Insect

insectinvasive-species2000s
Range
Range
Peak
Peak
Declared extinct
Declared extinct
Status
Rediscovered

Summary

The Lord Howe Island stick insect (Dryococelus australis, Montrouzier, 1855) is a large, heavy-bodied, glossy-black flightless phasmid endemic to the Lord Howe Island group in the Tasman Sea. Adults reach roughly 12 to 15 centimeters in length and can weigh around 25 grams, with females larger than males. Its bulk and dark, hard-shelled body earned it the local names land lobster and tree lobster. For most of the twentieth century it was believed to be extinct.

The insect's fate was sealed in 1918, when the supply ship SS Makambo ran aground at Lord Howe Island and black rats (Rattus rattus) came ashore. The rats found the large, slow, flightless phasmids easy prey, and within a few years the species had vanished from the main island. By around 1920 no living stick insects could be found, and Dryococelus australis was regarded as extinct.

Yet rumors persisted. Climbers visiting Ball's Pyramid, a sheer volcanic sea stack roughly 23 kilometers from Lord Howe Island, had reported a dead specimen and signs that something like the lost insect might survive there. In February 2001 scientists David Priddel and Nicholas Carlile, with ranger Dean Hiscox, climbed the stack and found a tiny relict population, on the order of 24 individuals, living beneath a single Melaleuca shrub.

What followed is the family's hopeful counterpoint, a genuine Lazarus story. A captive-breeding program begun at Melbourne Zoo in 2003, built from a handful of founders, has since reared thousands of insects. With the eradication of rats and mice from Lord Howe Island completed in 2019, the long-term goal of returning the land lobster to its home island has moved within reach.

Decline Timeline

1855
Species described
Dryococelus australis is described by Montrouzier; the large flightless phasmid is endemic to the Lord Howe Island group.
1918
SS Makambo runs aground
The supply ship wrecks at Lord Howe Island and black rats come ashore, exposing the defenseless stick insects to a new predator.
c. 1920
Presumed extinct
Within about two years the rats have eliminated the phasmid from Lord Howe Island, and no living individuals can be found.
20th century
Rumors from Ball's Pyramid
Climbers visiting the sea stack roughly 23 km away report a dead specimen and signs that the insect might persist there.
February 2001
Rediscovery
David Priddel and Nicholas Carlile, with Dean Hiscox, climb Ball's Pyramid and find about 24 living insects under a single Melaleuca shrub.
2003
Captive breeding begins
Founders are collected and a breeding program is established at Melbourne Zoo; founder female Eve nearly dies but is revived and goes on to lay hundreds of eggs.
2010s
Thousands reared
The captive program produces thousands of insects, with colonies and eggs later distributed to institutions overseas.
2018-2019
Rodent eradication carried out
After more than fifteen years of planning, an island-wide baiting operation in 2019 removes black rats and house mice from Lord Howe Island.
2019 onward
Path to reintroduction
With the eradication subsequently confirmed successful, the central barrier to returning the stick insect to its home island is removed.

Profile

Dryococelus australis is one of the largest and most distinctive of all stick insects. Adults are heavy, glossy, and black, with a thick, segmented body reaching roughly 12 to 15 centimeters and a weight of around 25 grams, far stouter than the slender twig-like phasmids most people picture. Females are larger than males. Unlike the great majority of stick insects, it is entirely flightless and wingless, a ground- and shrub-dwelling animal rather than a flier.

The species was endemic to the Lord Howe Island group, a small, isolated landmass in the Tasman Sea between Australia and New Zealand. Before the twentieth century it was reportedly common there, sheltering by day among vegetation and plant debris and feeding by night. Its size, its slowness, and its flightlessness, traits that posed no problem on an island free of mammalian predators, would prove catastrophic once such predators arrived.

The popular names land lobster and tree lobster capture both the insect's appearance and the way it was regarded: a large, armored, almost crustacean-looking creature unique to one island. For decades the only Dryococelus most people would ever see were dead specimens and old descriptions, because the living animal was thought to have been gone since the early 1920s.

The Decline

The decline of the Lord Howe Island stick insect was sudden and almost entirely the work of a single introduced predator. In 1918 the supply ship SS Makambo ran aground at Lord Howe Island, and black rats escaped ashore. The island's fauna had evolved with no such predator, and the large, flightless, slow-moving phasmid was acutely vulnerable. The rats preyed on the insects directly and ate their eggs and young.

The collapse was rapid. Within roughly two years the stick insect had disappeared from Lord Howe Island, and after about 1920 no living individuals could be found there. The species was written off as extinct, one of the clearest cases on record of an invasive mammal eliminating an island endemic. On the main island, that judgement was correct: Dryococelus australis never recovered there.

What almost no one expected was that a fragment of the species might survive elsewhere. Persistent reports surfaced from Ball's Pyramid, the precipitous sea stack lying roughly 23 kilometers from Lord Howe Island, including a dead specimen found by climbers. These hints were enough to suggest that, against the odds, a tiny population might cling to that bare and almost vegetation-free spire of rock, beyond the reach of the rats that had destroyed it everywhere else.

The Endling

For about eighty years the Lord Howe Island stick insect was counted among the lost. From around 1920 it was simply absent, an island endemic remembered in collections and in the standard accounts of extinction caused by introduced rats. The animal had been large and conspicuous, yet it had slipped away within a few years of the Makambo wreck, and no living individual had been seen for the better part of a century.

Then, in February 2001, the story reversed. Following the rumors from Ball's Pyramid, scientists David Priddel and Nicholas Carlile, with ranger Dean Hiscox, climbed the sea stack and, on a narrow terrace high above the water, found stick insects alive beneath a single Melaleuca shrub. The relict population was tiny, on the order of two dozen individuals, sheltering by day in moist plant debris at the base of that one bush. It was, for a time, described as the rarest insect in the world, the entire species reduced to one shrub on one rock.

That the land lobster had survived at all, on so meager a foothold, so far from its vanished home, is the rare extinction case that turns the other way. The insect had not been resurrected; it had simply never quite died, held on through decades of presumed extinction in a place no rat could reach. The task that began in 2001 was not to mourn an endling but to rescue a survivor.

Why It Vanished

01
Introduced black rats
Rats that came ashore from the wrecked SS Makambo in 1918 preyed on the large, slow phasmids and their eggs, wiping the species off Lord Howe Island within a few years.
02
Flightlessness and size
Being heavy, wingless, and slow made the insect easy prey; traits that were harmless on a predator-free island became fatal once mammals arrived.
03
Island endemism
The species existed only on the Lord Howe group, so a single introduced predator on that small landmass was enough to eliminate it almost entirely.
04
No predator defenses
Having evolved without ground-hunting mammals, the phasmid had no behavioral or physical defenses against rats.
05
A precarious refuge
Survival depended entirely on one tiny, almost inaccessible population on Ball's Pyramid, clinging to a single shrub and exposed to storms, rockfall, and chance.

Aftermath

The 2001 rediscovery launched one of the most closely watched insect-recovery efforts in the world. In 2003 founders were collected from Ball's Pyramid and a captive-breeding program was established, centered on Melbourne Zoo. Early progress was perilous: one of the original pair, the female known as Eve, fell gravely ill and laid only a handful of eggs before keeper Patrick Honan revived her with a hand-fed mixture, after which she went on to produce hundreds of eggs. From such fragile beginnings the program grew, and by the 2010s thousands of insects had been reared, with eggs and colonies later shared to institutions abroad.

The insect's return to its home island, however, depended on removing the predator that had destroyed it. After more than fifteen years of planning, the Lord Howe Island Rodent Eradication Project carried out an island-wide baiting operation in 2019 targeting both black rats and house mice. The eradication was subsequently confirmed successful, removing the central obstacle to reintroduction and reshaping the conservation prospects of much of the island's native fauna.

The Lord Howe Island stick insect now stands as the family's hopeful counterpoint: a species declared extinct around 1920, found alive on a sea stack in 2001, multiplied into the thousands in captivity, and given, with the rats finally gone, a credible path back to the island it was driven from. The recovery is not complete, but the land lobster is one of the very few presumed-extinct animals whose case file ends not with a last individual but with a second chance.

Lessons

  1. A single introduced predator can erase a defenseless island endemic within a few years, as the rats did after the Makambo wreck.
  2. Presumed extinction is not always final: a tiny, isolated refuge can preserve a species long after it is written off, as Ball's Pyramid did here.
  3. Captive breeding from a handful of founders can rebuild a population, but it hinges on individual care and a great deal of luck in the early stages.
  4. Recovery is incomplete without addressing the original cause; reintroduction depended on eradicating the rats that drove the species out.
  5. Rediscovery raises the stakes rather than ending the story, turning a closed extinction case into a long-term conservation obligation.

References