Huge 'Tree Lobster' Not Extinct After All

View Images An adult female tree lobster is roughly the size of a human hand.

Photograph by Rohan Cleave, Melbourne Zoo, Australia

A large stick insect from a remote Australian island is back from the dead.

It's hard to miss a Lord Howe Island stick insect, sometimes called a "tree lobster." Their blackish brown bodies grow to be nearly six inches long, and the robust insect has a sturdy abdomen and six long legs.

For decades it appeared to be extinct, but new DNA research reveals that may not be the case. To understand the insect's complicated and sudden revival, you have to go back to a small island as it was 100 years ago.

The massive population decline of these stick insects began with a shipwreck in 1918, on their namesake Lord Howe Island, a small, lush landmass jutting out of the ocean off the east coast of Australia. In addition to its crew, the ship contained a horde of rats that quickly invaded. With no larger mammals to predate on the rats, their population exploded. The stick insect was eventually classified as extinct in 1983, along with 12 other insect species and five bird species.

Then, in 1960, a group of rock climbers visited another small volcanic rock island nearby, named Ball's Pyramid. It was there that they found what appeared to be the dead remains of the "extinct" stick creatures. It wasn't until 2001 that researchers returned to Ball's Pyramid. Atop a tea tree, 213 feet above sea level, sat a few living examples of what appeared to be Lord Howe Island stick insects.

In the year that followed, several of the insects were collected and placed in a captive breeding program at the Melbourne Zoo.

However, for nearly a decade, the identity of the insects was the subject of debate. Visually, the captive-bred stick insects looked different—they had darker brown bodies and their back legs were thinner than museum specimens of the stick insects from Lord Howe Island.

It wasn't until genome sequencing was conducted on both the museum specimens and the captive-bred stick insects that scientists realized they had a less than one percent genetic variance—enough to officially classify them as the same species. These findings were recently published in the journal Current Biology.

The subtle physical differences are still a mystery. Researchers think it may have to do with variances in environmental conditions or in an individual insect's age.

The study's researchers point to it an example of not only a species success story, but also how advancing technology has helped scientists study older generations of extinct or threatened species.

Exactly what constitutes a species has long been the subject of debate. One report from Museums Victoria in Australia listed 26 different concepts for defining what differentiates one species from the next. According to Alexander Mikheyev, the study's lead author, the team deemed it a news species based on whether or not the two organisms could swap genetic material.

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This debate matters for conservation purposes, particularly on Lord Howe Island, where the Australian government plans to eradicate the invasive rat population—and possibly reintroduce the stick insects.

For Mikheyev, the findings represent something more existential. In addition to studying evolutionary changes using centuries-old museum specimens, he hopes other species facing extinction are given more potential to survive.

"We have a second chance, it gives us a sense of hope," he said.