Photos by Elyse Butler
Hadfield inspects the undersides of the leaves of a short ‘ohi‘a tree where the nocturnal snails hide during the day.
“Here’s one,” he says. “It’s a beaut.” The shell is a creamy white conical spiral about as long as the tip of your pinkie. Called kahuli (to change or overturn) in Hawaiian, it perches on an intact leaf—no chewed holes. That’s because these snails don’t eat plants; they feed on mold growing on the leaves.
Dangling from a strip of surveyor’s tape affixed to a nearby ‘ohi‘a, five more snails huddle like a bunch of pointy berries. Hadfield notes other evidence of human intervention: rat bait stations placed among the trees and along the fence line.
The snails at this location are all Achatinella mustelina, a species found only in the Wai‘anae range. Yet they’re as diverse as a litter of poi dogs. Achatinella shells are colorful: pure white to pure black, greens, yellows and browns. Most have horizontal stripes. Hadfield examines a shell with lines that also run vertically.
“We call these plaids,” he says.
Snail savior: Biologist Michael Hadfield searches an 'ohi'a tree in the Honouliuli Forest Reserve for a critically endangered native land snail. Once abundant in O'ahu's forests, the sensitive and slow-growing kahuli have suffered from habitat loss, predation and a nineteenth-century mania for shell collecting. Through a captive breeding program at the University of Hawai'i at Manoa, Hadfield hopes to re-establish kahuli in the wild.
Today it is illegal to take live snails or their shells from the wild. In the past, however, kahuli were an important part of native culture: Making kahuli shell lei was a Hawaiian tradition, and prized kahuli lei heirlooms are still passed down within families. Kahuli are also known in chants and legends, sometimes referred to as pupu kani oe, or “singing snails.” The name of King Kamehameha III’s summer cottage in Nu‘uanu is Kaniakapupu, or “song of the land snail,” so called because the area was once a rich habitat for kahuli (today it’s mostly a bamboo forest, and the snails are gone). There’s much debate about whether snails can actually sing; so far there’s no scientific evidence that snails vocalize. One explanation is that the chirping of crickets was attributed to the snails, as both are active at night.
Perhaps more important than whether the snails actually sing is the phrase itself, which reflects a Hawaiian relationship with the ‘aina (land). Biologist and Hawaiian cultural practitioner Samuel M. ‘Ohukani- ‘ohi‘a Gon III cites a love chant about the goddess La‘ieikawai in which the singing of the snails is a sign that the bride and groom should meet:
O ka leo o ke kahuli
Aia i ke kuahiwi
O ka pupu kani oe.
(The voice of the snail
There in the uplands
It’s the singing shell.)
“Hawaiians give intimate attention to even the smallest signs seen or heard in the landscape,” explains Gon, “and accord these great significance, as in the name of a chiefly residence or the single most important sign that a goddess should be betrothed.”
In the mid-nineteenth century kahuli snails caught the fancy of European collectors who succumbed to “shell fever” of epic proportions. Descendants of missionaries and other kama‘aina residents scooped them up by the hundreds of thousands. They paid Hawaiians to fill containers with snails and pack them out on horseback. Hawaiian tree snails, like many other flora and fauna of the period, fell victim to a Victorian-era passion for collecting souvenirs. That only a few collectors kept accurate records is a tragedy: Volumes of data were lost because collections were often a hodgepodge of snails from many sites.
Collecting was only one factor, though, in the kahuli’s disappearance. Development, logging, wildfires and the introduction of exotic plants shrank native forests. Two introduced predators also took a toll: the rat and the rosy wolf snail. The state Department of Agriculture deliberately introduced wolf snails in 1955 as biocontrol against giant African snails, also introduced, that had become a serious yard and garden pest. But the wolf snail isn’t picky; it eats almost any snail, even other wolf snails. It devours the defenseless kahuli, leaving an empty shell. If that weren’t problem enough, it’s been recently discovered that alien Jackson’s chameleons also gobble up kahuli, shells and all. And so the kahuli, once superabundant in the forests of O‘ahu, rapidly declined. Today more than 75 percent of all of Hawai‘i’s native land snails are extinct. At least half the species of Partulina are extinct, and only ten Achatinella species remain. All are critically endangered and federally protected.
Achatinella mustelina, feeding on the underside of an 'ohi'a leaf.
Breeding snails and putting them back into the wild might sound simple. After all, garden snails are prolific and will ravage your Manoa lettuce without any help. And like other snails, kahuli are hermaphrodites, blessed with both male and female parts (yes, one species of kahuli can self-fertilize). Since every member of the population is potentially a mother, the reproductive rate is typically high for snails. But kahuli aren’t your garden-variety snails. Most snails mature quickly and lay hundreds of eggs, but kahuli take about four years to mature and each bears only four to seven young per year, one at a time. Adding to the challenge, kahuli live virtually all of their long lives (ten to twenty years) on a single native tree or bush, feeding on the mold specific to the leaves of that plant and nothing else.
In the days before introduced predators, when there was abundant native habitat, these traits weren’t a disadvantage. “Even producing only a few keiki [young] per year, the snails could accumulate in great numbers,” says Hadfield. “Now many of the native trees on which the snails then lived are gone or greatly reduced, and predators shorten reproductive life spans.” Assuming, that is, the snails survive even long enough to reproduce—research shows that fewer than 10 percent make it that far, says Hadfield.
The lab has had amazing success breeding the snails in captivity, but it’s been far from painless. “Creating an environment that duplicates conditions in the field is difficult and not always successful,” Hadfield notes. “We’ve had many failures while we learned how to do it—no one had done it before—and it’s often been terribly disappointing.” But the successes have far exceeded the failures: The lab is now home to 1,500 snails, most of them propagated from a handful of parents. Achatinella lila is emblematic of the lab’s achievements: From six individuals there are now five hundred. The lab has nine of the ten remaining Achatinella species, though that number is likely to drop to eight in the near future: The lab’s lone Achatinella apexfulva is probably the last survivor. No one has seen it in the wild for more than a decade.
While some populations have been living and reproducing in the lab for twenty years, returning them to the forest remains the sticking point: The predators are still out there, and the habitat is still depleted. “When the snails are put back into the field,” says Hadfield, “survival declines to what it typically is, which is pretty poor.”
But all is not yet lost, and though the solution is expensive and labor intensive (and by no means assured of success), the snails have found an unlikely ally in their fight for survival.
Kahuli are found today in only a few remote areas like the Honouliuli reserve, and in some places the snails have become a flash point in conflicts over land use. Kahuli are one of more than forty endangered species in Wai‘anae’s Makua valley, where the US Army conducted live-fire training from WWII until 2001, when a lawsuit by local activists forced them to stop. The Army is now collaborating with UH to protect all endangered species in the valley; they are assisting with invasive plant removal and native habitat restoration.
The state Natural Area Reserves System has constructed two “exclosures”— fenced areas with electrified barriers—to keep predators like rats and wolf snails away from kahuli populations. The Army is working on a third, one that “will incorporate new barriers we designed in cooperation with the UH lab. Hopefully it will lead to more exclosures to protect snails both on and off Army land on O‘ahu,” says Army media relations chief Loran Doane. One hundred fifty A. mustelina that the Army collected from the Wai‘anae range are waiting today in the UH lab to be returned to the spot from which they were removed once an exclosure is built, possibly as early as the beginning of 2011.
Why go to so much trouble for a little snail whose chances of survival, even with help, are uncertain? “There are a thousand things in me that rebel against their extinction,” says Hadfield. “As an evolutionary biologist, I know how these things came to be, how it took millions of years for these just to exist. I would like to see habitat restored so that someone’s grandkids can have some idea of what a pure and complete Hawaiian rainforest looked like.”
Even something so small as a snail could be a bellwether of our shared future, says Hadfield. “Those who study climate change predict that tradewind showers will disappear. If that happens, the rainforest, the snails and everything else disappears, too. I don’t know what the future is, but there are places that give hope. We’re still learning how to grow and protect. … That’s why we do science. If I were a complete pessimist,” he says, “I wouldn’t do this.”