MOVIE moguls would die for this story. It is packed with adventure and has more cliffhangers than your average miniseries. The only real challenge is the casting, because the central characters of this tale aren’t humans – they are giant insects. That may not deter all the hotshot producers who read żěè¶ĚĘÓƵ, but just in case the story never reaches a screen near you, here it is. It begins almost a century ago…
On 14 June 1918, the supply ship Makambo struck a submerged rock off Lord Howe Island, a volcanic dot 780 kilometres north-east of Sydney, Australia. The cargo was salvaged and taken ashore to the island, which is a semi-tropical paradise, lushly forested and rich in plants and animals found nowhere else. Unfortunately, the ship’s rats came ashore too. They spread rapidly, soon dispatching several island species, including a giant wingless stick insect, or phasmid. By the 1930s, the Lord Howe Island phasmid (Dryococelus australis) was written off as extinct.
By all accounts, it had been a spectacular insect, so big the islanders called it the land lobster. Females grew up to 15 centimetres long, with bodies as thick as a finger and long, stout legs equipped with hooks. The slightly shorter males had peculiarly massive thighs armed with evil-looking spines. They couldn’t fly but they could run surprisingly fast. Until the Makambo incident, these giant phasmids had been so common that islanders used them as fishing bait. The only account of their habits was left by an Australian entomologist called Arthur Lea, who visited the island in 1915. He described them as nocturnal, coming out at night to feed and then retreating to damp hollows in trees for the day. One hollow might contain dozens of phasmids and, according to Lea, could be easily located by the great piles of dung at the base of the tree.
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Then they were gone. The last one was seen in the 1920s and despite regular surveys, there has been no trace of them on the island since.
However, in 1964, a rock climber found a dead phasmid, not on Lord Howe Island but on Balls Pyramid, a remote spire of rock 24 kilometres to the south-east. Another climber found two more dead phasmids there in 1969, one lodged in a bush, the other as part of a seabird’s nest – a stick insect mistaken for a stick. Was the giant phasmid alive and well and living somewhere on Balls Pyramid? It seemed improbable. This was a creature of warm, damp forests that needed living trees with sizeable hollows to hide in. Balls Pyramid is the world’s highest sea stack, its sheer cliffs rising 550 metres. Isolated, exposed to high winds and with no apparent water supply, the islet has just a few scraps of vegetation and no trees. To everyone’s disappointment but no one’s surprise, every expedition that went in search of giant phasmids drew a blank.
Night of the phasmids
Then in February 2001, a party of four entomologists and conservationists landed on Balls Pyramid to survey its flora and fauna. This was not a job for the faint-hearted. “The rock comes straight up out of the water and even at the best of times there’s a 6-metre swell,” says David Priddel of the New South Wales Department of Environment and Conservation, who led the expedition. “When you jump onto the pyramid the boat drops away beneath you.” Getting off the pyramid is even harder. “It’s safer to jump into the water,” he says, despite the waiting sharks.
After six decades without a sighting, the team did not expect to find living phasmids. “We went with open minds but we had designed our survey to show it was not there,” Priddel says. They searched the one part of the stack they could reach without specialised climbing gear, a section of the south-east corner where a series of terraces extends about 120 metres up from the sea. “Climbing the pyramid is the scariest thing I’ve ever done,” he says. “It’s the only time I’ve ever heard my knees knock together.” Scrambling from one crumbling ledge to the next, they looked out for anything that might indicate the presence of stick insects. It hardly seemed worth it: there was not a single tree nor anywhere else a phasmid could hide by day.
The biggest plant was a shrub called Melaleuca howeana, a tea tree native to Lord Howe Island. About 65 metres up they came across a particularly large melaleuca bush, and scrutinising the ground beneath it they were amazed to find a scattering of droppings – some still green and moist. A large insect clearly lived on that ledge. If it was a phasmid, it would not show itself in daylight. Someone would have to return after dark.
Back at camp near the base of the rock, the two fittest and most competent climbers, Dean Hiscox, a Lord Howe Island ranger, and Priddel’s colleague Nicholas Carlile, readied themselves for a late-night ascent. “They weren’t keen to go,” recalls Priddel. “They were already exhausted and it’s a dangerous climb at night.” They climbed by torchlight and, once on the ledge, played their lights over the bush. Within minutes they found two female giant phasmids grazing on the new red leaf tips at the ends of the branches. Further investigation turned up a third, an immature female. Excited, they searched several smaller shrubs on the same ledge, but found no more. “When they returned and told us we thought they were winding us up,” says Priddel.
The next morning, the four of them went back to the terrace. The ledge sloped steeply and most of the ground was dry, dusty and unstable. The bush was a good size, but its trunk followed the slope of the terrace, and two pairs of seabirds were nesting in the canopy. Behind it, though, conditions were better. Water seeped from a seam in the rockface, dampening the area between cliff and bush. A few scruffy plants had colonised the area and over time dead plant material had built up into a layer of compost a metre deep. “This is the only place where there is any moisture,” Priddel says. “The animals burrow into the heap and spend their days there.”
The discovery was big news. The land lobster was not extinct. But it was the rarest insect – probably the rarest invertebrate – on the planet. Its survival on Balls Pyramid was little short of miraculous. How had such big, flightless creatures got there? “One thing’s certain, they didn’t get there by walking,” says Priddel. The two islands have never been linked by dry land. The stick insects might have been carried there on floating plant debris or by seabirds collecting nest material. They need not even have been alive: dead stick insects can contain one or two viable eggs. Priddel thinks they were probably taken there as bait by fishermen. “However they got there, their survival was astonishing,” he says. “There is nothing like their natural habitat on the pyramid and yet they must have been there 70 years and maybe much longer.”
In March 2002, Hiscox and two colleagues from Lord Howe Island returned to count the phasmids. This time they found 24, including a few males, on several bushes. It was an improvement, but the entire population was still confined to an area measuring 30 metres by 6 metres on one ledge. The risk of extinction was extremely high: one small landslip and they would all end up in the sea. Their only prospect of survival was a captive breeding programme. Stick insects generally breed well in captivity, so it should have been easy. It was to prove anything but.
The conservationists’ first challenge was getting permission to move some of the phasmids from the pyramid. Two years after their discovery, the authorities back in New South Wales, which administers Lord Howe Island, and the island’s own governing body, agreed to allow two pairs to be captured. One was to found a population at Melbourne Zoo under the care of stick-insect expert Patrick Honan. The other was to go to Sydney entomologist Stephen Fellenberg, a highly successful stick-insect breeder.
The collection was planned for February 2003. For a while it looked as if foul weather would wreck the mission, but when the local weather station predicted 20 hours of relative calm, Hiscox and two colleagues made a dash for Balls Pyramid and climbed to the ledge. They returned with four phasmids, which they delivered safely to Honan waiting in the boat below. Back on Lord Howe Island, Honan spent all night watching the insects. “On that very first night they began to mate,” he says.
It was a good start, but any hopes that captive breeding might prove simple were soon dashed. With practically no knowledge of the species and so few animals there was no question of experimenting to find the best living and breeding conditions. Everything had to be done slowly and carefully without putting the precious phasmids at risk.
The first crisis came within weeks. Eve, the Melbourne female, laid a batch of nine eggs – then stopped eating. “She went downhill fast,” says Honan. “We were desperate to save her.” But no one had any idea what was wrong. Perhaps she was egg bound, unable to lay her next batch. The zoo’s vets frantically X-rayed the females of as many species of stick insect as they could. Most had dozens of eggs inside them. They X-rayed Eve: she had only six. Her gut, though, was full of air, which is known to be a sign of stress in vertebrates.
Sorting out the stress problem could wait, however: the immediate challenge was to get some food into her. “She was sitting in my hand with her legs curled up, pretty much dead-looking. We had to do something or she was going to die,” says Honan. He made up a solution of glucose and calcium and ground up melaleuca leaves, then, holding her upside down under a microscope, dripped it onto her mouthparts. “She took in the liquid and a couple of hours later she was as good as new.” Eve lived another 18 months and laid a further 260 eggs. In Sydney, Fellenberg was not so lucky. Within six weeks both his phasmids had died. He was left with 21 eggs.
Stick insect eggs take up to nine months to hatch. With just two captive phasmids left, the wait was nerve-racking. On 7 September 2003, Australia’s Threatened Species Day, one of Eve’s eggs hatched. Since then the breeding programme has lurched from one crisis to another. The hatch rate of eggs and survival rate of nymphs have been disappointing. “Hatching success is about 20 per cent, and about 30 per cent of the nymphs reach adulthood,” says Honan. Terrifyingly, at one point there were no phasmids at all, just a lot of eggs and crossed fingers. To everyone’s relief, some hatched and matured and breeding began again.
“Some pairs consistently sleep together in a kind of three-legged embrace”
Over the past three years, success rates have improved as the team discovers more about the biology of giant phasmids. Most stick insects hang in a tree and do little but eat, but these are very active and responsive. “They seem more aware of what’s going on around them and of each other,” says Honan. Unlike other stick insects, male and female phasmids appear to develop some sort of bond, and the male’s behaviour seems to be determined by what the female is doing. “That’s very unusual for any insect.” Some pairs consistently sleep together in their daytime refuge, the male wrapping his legs over the female in a kind of three-legged embrace. What’s more, while other female phasmids hang from a twig and drop eggs to the ground one at a time, these bury a batch in the soil. Their nocturnal habits are also odd for a stick insect. Emerging nymphs are active by day: they are small and bright green and when threatened sway gently like a leaf. “When you are as big as the adults such camouflage isn’t going to fool anyone,” says Honan. “So they grow dark and come out at night.”
The breeders have learned to keep their phasmids in conditions rather better than those on Balls Pyramid, and more like those in the forests of Lord Howe Island. Warm, fairly constant temperatures and near 100 per cent humidity seem to increase the adult survival rate. The next big challenge is to improve their diet. “We think there might be something lacking and that’s why the success rate is so low,” says Honan. On Lord Howe Island the phasmids would never have eaten a cliff-growing plant like melaleuca, but there is no record of what they did eat. “As flightless animals, they probably stick to what they start eating when they first emerge,” says Honan. The captive ones have been reluctant to change, but Honan is slowly weaning them onto more nutritious vegetation.
Today, there are 50 Lord Howe Island phasmids at Melbourne Zoo – 10 adults and 40 nymphs – and a thousand eggs. In Sydney, the offspring from Fellenberg’s first eggs died out. He is now incubating a new batch from Melbourne, which are due to hatch at any time. “It’s the first time we have had so many live phasmids at one time,” says Honan. This is a real landmark, with captive animals now outnumbering wild ones. The Balls Pyramid population is still hanging on, but numbers vary from year to year at between just 20 and 30. “Now we’ve got a colony in captivity we are not going to lose them,” says Priddel.
It looks as if this extraordinary creature has been rescued from almost certain extinction. The species’ future will only be assured, however, if giant phasmids can be reintroduced to their native Lord Howe Island. That means getting rid of the rats. An eradication programme is planned, but as with everything in this story it won’t be easy. Poisoning the rats is simple. The hard part is protecting other animals such as the endangered Lord Howe Island woodhen. Conservationists will have to round up several species and keep them in captivity for the duration without harming any in the process. “I reckon it would take six weeks to kill the rats,” says Priddel, “and five years to make the preparations.” He finds that frustrating. But for a species that has spent 70-odd years clinging to a rock, maybe it is not so long.
