Crawling across the gloved hand of San Diego Zookeeper Kyle Cassell, a feisty Lord Howe Island stick insect had no idea it wasn't supposed to be there. Nicknamed “wood lobsters” because some can grow up to eight inches, the plucky insects scurried about Cassell's hand like scurrying dogs, seemingly desperate to stop him from getting a good photo.
This mischievous stick insect was so close to extinction that it has been dubbed “the world's rarest invertebrate,” but the insect, housed at the zoo's McKinney Family Invertebrate Breeding Center, is compelling evidence that an international effort led by Melbourne Zoo in Australia may be able to save the Lord Howe Island stick insect from extinction.
Insects have received far less conservation attention than their fascinating vertebrate cousins like tigers and pandas, yet insects and other invertebrates are the spineless pillars of ecosystems, playing vital roles as pollinators, predators, prey and decomposers.
Through conservation breeding, which includes efforts to raise insects like Lord Howes in large zoos like those in San Diego and Melbourne, humans could save declining populations and restore the vital functions these animals perform.
But for this to happen, there needs to be suitable habitat for the animals to return to, and the humans who live there need to want them to return in the first place.
The Lord Howe Island stick insect isn't as flashy as other insects in the order Phasmodium. Predominantly brown in color, this insect takes the “stick” part of its name seriously. But what this stick insect lacks in flashy wings and vibrant colors, it makes up for with simple, rustic charm.
The island for which it is named lies about 370 miles east of mainland Australia and was discovered in 1788 by British naval officer Henry Lidgibird Ball. Human settlement followed in 1834. The situation of the island's native species rapidly deteriorated in 1918 when a trading ship accidentally released stowaway rats; by 1921 the rats had wiped out the island's stick insect population.
In 1964, hopes began to swirl that the bug was still alive after a rock climber discovered a recently dead bug on Ball's Pyramid, a volcanic island that juts violently out of the sea about 14 miles southeast of Lord Howe Island.
“It's a pretty desolate landscape,” says Melbourne Zoo's invertebrate life sciences manager Kate Pearce, “and there's not a lot of soil.”
Subsequent efforts to find living stick insects on Ball's Pyramid continued without success until 2001, when a search team scaled the pyramid at night and found two female stick insects on a small tea tree. At the time, the live population of stick insects totaled about 24, struggling to survive on the edge of the pyramid.
Australian researchers quickly organized a rescue mission: In 2003, the Lord Howe Island Commission, working with the New South Wales government, sent scientists to collect pairs of stick insects from Ball's Pyramid and send them to experts who could breed them.
“We chose Melbourne Zoo because of their experience with invertebrates,” says Pearce, who has overseen the zoo's stick insect program since 2011. The Melbourne team learned to care for the two stick insects, named Adam and Eve, through risky trial and error.
Pierce's predecessor, Patrick Honan, stayed with Adam and Eve overnight to monitor their health. Eve was unwilling to lay eggs and eventually “became quite ill,” Pierce said.
Honan created a “magic potion” of sugar, calcium, and ground tea tree leaves, which he gently dropped into Eve's mouth. Keepers then placed a tray of sand in Eve's enclosure, and she happily laid her eggs in it. Most stick insects hang from branches and then drop their eggs on the ground. The Lord Howe Island stick insects do the same, but for some reason, Eve preferred the sand.
Those early efforts paid off: Melbourne Zoo now houses about 500 Lord Howe Island stick insects, and in 2017 brought in another female (named Vanessa, after the rock climber who discovered her) from Ball's Pyramid to diversify the captive gene pool.
The San Diego Zoo is also struggling: Of the eggs sent from Melbourne in 2012, only about 20 percent hatched and none of the hatchlings survived.
A second attempt in 2015 saw invertebrate zoologist Paige Howorth pick up the eggs herself – “I was hoping Qantas would roll out the red carpet for us,” she joked – but the stick insect population eventually declined too.
A third attempt, with 600 eggs shipped in 2022, was successful, bringing the zoo's population to at least 400 now.
In their San Diego habitat, the Lord Howe Island stick insects live a more comfortable life than they did at Ball's Pyramid; the vivarium's climate mimics their island home, even providing a constant, gentle breeze with fans. A team of 13 keepers, led by Dr. Howarth, look after the remote stick insects, along with separate enclosures of tarantulas, praying mantises, beetles, crickets and horseshoe crabs. The team's mascot is a coconut crab named Kenny, who was busy molting in the vivarium's soil on my recent visit.
The first large-scale invertebrate conservation breeding program was launched in 1986, when a federation of zoos worked with the International Union for Conservation of Nature to save a group of more than 100 tree snail species.
Parchurid, Like many snails, they help keep the environment clean by eating fungi and dead plants. This group is spread throughout Polynesia, with nearly every island home to a unique species that looks and behaves differently.
“Snails have been the subject of evolutionary research for over 100 years,” says Paul Pearce Kelly, curator of invertebrates at the Zoological Society of London and leader of the snail research program, “and they are the snail equivalent of Darwin's finches.”
They were famous, so when their numbers began to decline because of an invasive predator called the rose-colored wolf snail, people took notice.
Efforts to reintroduce the gastropods to their native habitat began in earnest in 2015 and have continued ever since. For example, in April 2023, the team released more than 5,000 snails on the French Polynesian islands of Tahiti and Moorea. More than 25,000 captive-bred wolf snails will be released into parts of the Pacific islands not yet invaded by wolf snails, in the hope that they will survive long enough to reproduce and form self-sustaining populations.
Capturing invertebrates is much cheaper than captivity than raising pandas or tigers, but it's not easy work. Despite decades of effort, some snails don't survive captivity. Capturing hundreds of animals means feeding hundreds of hungry animals. Melbourne Zoo “grows thousands of plants just for the stick insects on Lord Howe Island,” Pearce said.
San Diego Zoo keeper Cassell called the phasmids “greedy.” While large zoos in warm climates like Melbourne and San Diego can meet the demand for leaves, many others cannot.
The captivity environment itself can also pose problems. Small populations can lead to inbreeding, which can shorten the lifespan of the insects and make them less likely to reproduce. Disease can also spread quickly in small spaces; between 2013 and 2015, Melbourne was hit by two outbreaks of bacterial infections that affected stick insects.
And being confined for long periods of time allows rapid reproduction in many invertebrates to literally evolve before our eyes: A 2021 study found that Melbourne stick insects have smaller eyes and fewer olfactory receptors over time, and researchers warned that this could impair their ability to survive in the wild.
Reintroducing invertebrates into the wild presents challenges in itself.
Christina Venables lives on Lord Howe Island and heads up the local government's Environment and World Heritage team. As well as looking after a captive colony of stick insects, she is also working to prepare the island and its people for the potential return of lobsters.
In 2019, authorities carried out a plan to rid the island of invasive rats. The plan appears to have been successful, with no live rats found on the island since August 2021. But while the animals responsible for the stick insects' decline have been eradicated, “we're not going to reintroduce them,” Venables said. “We need to consult with local people and get their cooperation.”
While many of the island's 445 residents are extremely proud of their home and the wildlife that lives there, some worry about what life will be like with the insects.
“No one on the island has ever lived with Phasmids anymore,” Venables says, so tales of Phasmids crawling noisily on roofs and plucking leaves from trees “may take on a life of its own”.
Venables is focused on educating local people about stick insects and the environmental benefits they provide, such as providing food for native birds and their waste helping to fertilise the soil.
While her captive population will not be on display, Venables plans to invite local people to visit their potential new neighbours and even help care for them “so they can get an idea of what phasmids are like”.
So what exactly is the Lord Howe Island bug? My inspiration came from the San Diego Zoo's Spineless Marvels exhibit, which features several stick insects. There, I saw one of the most unusual invertebrates on the planet standing proudly front and center, silent and still, with a turd stuck to its head.