Lord Howe Island stick insect

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In the late 1990s, Carlile and Priddel worked for the conservation authority in New South Wales, Australia. Part of their remit was to deliberate on requests for expeditions to climb Balls Pyramid, the tallest volcanic stack in the world; a ragged rock that rises almost vertically out of the sea. For a combination of safety and environmental reasons, access to this island has been restricted since the 1980s. But back in the 1960s, climbers scaling its cliffs found pieces of exoskeleton – the hard casing that covers insects’ bodies – that might have belonged to the Lord Howe Island stick insect, a species that was thought to have gone extinct at start of the 20^th century. Thirty years later, that find seemed to be prospective climbers’ go-to excuse. “We’d get requests from people saying they were going to find this stick insect,” says Carlile, “but then you’d look at the list of people and there wouldn’t be an entomologist [insect specialist] on there! At some point Dave just turned to me and said ‘you know, the only way we’re going to put a stop to this is if we go out there and prove the animal is not there.’”

There were solid reasons for the scientists’ scepticism. The Lord Howe Island stick insect hadn’t been seen alive since the early 20^th century. And even then, it had lived 20 km away, on the island it was named after. Explorers called it a tree lobster, because the lobster-sized insect lived in hollowed out tree trunks in the rainforest. On Balls Pyramid, the largest plants are spindly bushes. “There isn’t a branch thicker than my arm [on Balls Pyramid],” says Carlile. It seemed extremely unlikely that a rainforest inhabitant could survive on the barren, exposed rock.

Conquering Balls Pyramid

In 2001, Carlile and Priddel set out to settle the matter for good. Not being insect specialists, they enlisted the help of two entomologists, Margaret Humphrey and Stephen Fellenberg. They also brought on Dean Hiscox, a local ranger who, being an experienced climber, could help them negotiate the crags and overhangs of Balls Pyramid. After all, there’s a reason the island is such a magnet for rock-climbers. Even getting onto it requires climbing skills. If you arrive on a calm day, your boat will be bobbing up and down on 2 metre-high waves, in front of a vertical rock face.  “You have to jump off the front of the boat when it reaches the highest point on the wall, grab on, and then climb up to the shelf,” Carlile explains, making it sound almost easy.

Once they’d done that, the team – minus Fellenberg, who’d had to drop out at the last minute due to an injury – spent the morning climbing up to the island’s greenest area. If there were Lord Howe Island stick insects anywhere on Balls Pyramid, this was the likeliest spot. They searched for the stick insects, and found none. As they were walking back down to their base camp, though, Carlile spotted something. Under a bush was some large insect poo. Humphrey speculated that it might belong to some large crickets the team had found earlier, but they couldn’t be sure. That evening, Carlile says, Priddel pulled him aside and pointed out that the stick insect was known to be nocturnal, so the only way they could be one hundred percent sure it wasn’t living on the island was to look for it at night. “He said to me, ‘I really struggled today, so I’m not going to ask you to climb tonight, because I can’t do it myself’, but I said ‘oh, no, I’ll be up for it, and I’m sure Dean [Hiscox] would be up for it,’” So Carlile and Hiscox braved the climb after dark. Near the bushes, Carlile – who specialises in birds – was surprised to see wedge-tailed shearwaters. These grey-brown seabirds dig burrows to build their nests in, and Carlile was amazed that they could find enough soil to dig burrows on the barren, rocky island. He didn’t ponder the issue for too long, though, because he found an even bigger surprise clinging to a bush: a Lord Howe Island stick insect. “I had a little instamatic camera in my pocket, and there were three photos left on the roll,” says Carlile. “I took photos realising they were the first images of a live [Lord Howe Island] stick insect. For us, it was ‘oh my God, we’re looking at something that has been extinct for 80 years, and no-one has ever seen it’ – and also… they were right! The guys in the ‘60s who I’d poo-pooed, were correct.” Carlile and Hiscox found another two of the insects on the same bush, but none on the other bushes. They took a moment to steady themselves before heading back to camp: “We had to really calm ourselves down for the descent, because we didn’t want to then fail in that attempt and for it to still remain a mystery!”

The next morning, the team all rushed back up to the bushes to do a survey before their boat came to pick them up. They found Lord Howe Island stick insect eggs buried in the soil. And they found only one place where the insects might take refuge during the day: the burrows dug by the wedge-tailed shearwaters that Carlile had spotted the night before.

Back from the brink

Having discovered that the Lord Howe Island stick insect was not extinct, Carlile and colleagues got to work setting up a recovery plan for the species. In 2003, scientists captured two pairs of stick insects on Balls Pyramid. One pair went to Fellenberg, while the other was taken to Melbourne Zoo. The zoo was chosen because the team of invertebrate keepers there had a lot of experience of caring for and breeding insects, but even they were up against a tough challenge. “When [the Lord Howe Island stick insects] first came we knew absolutely nothing, except for the plant species that they were found feeding on, on Balls Pyramid,” says Rohan Cleave, who now heads the species’ captive breeding programme at the zoo. As they learned more about what the stick insects need in order to thrive, the team’s results improved steadily. Over the years, they have successfully hatched over 14,000 young insects; the 13^th generation of Lord Howe Island stick insects at the zoo laid eggs in early 2017. Thanks to this success, experts have been able to take stick insects from Melbourne Zoo to set up captive populations in Boston, Bristol, Toronto and on Lord Howe Island. If rats – which played a key role in driving the stick insects to extinction – are eradicated from Lord Howe, stick insects bred in captivity could one day be released back into their original habitat.

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