David Sischo still remembers with chagrin the time he and his young brother discovered hordes of snails in his grandparents’ yard and began throwing them on the road.
"They were the pest snails that eat your garden but I vividly remember my parents coming out and there were all these snails smashed on the road — 150 squashed snails."
So maybe it’s karma that explains why Sischo is now the state’s point man in its efforts to save Hawaii’s native tree snails, or kahuli. He is coordinator of the state’s Snail Extinction Prevention Program, established by the Department of Land and Natural Resources last year in response to an alarming decline in the number of native snails in Hawaii.
Scientists believe as many as 1,500 distinct kinds of snails in 10 different families once existed in the islands, having arrived millions of years ago after hitching a ride here on birds and driftwood. By the time humans conducted their first snail counts, they identified only about 750 species of Hawaiian terrestrial snails — still a stunning representation of evolutionary species radiation.
Now it is estimated that as much as 90 percent of the diversity has been lost.
To lose these creatures is to lose a part of Hawaii. With their lovely cone-shaped shells and their subtle colors twisting into a delicate spiral, Hawaii’s tree snails have been described as the "jewels of the forest."
According to Hawaiian folklore, they are renowned for their ability to sing. In fact, more than 30 works of traditional Hawaiian poetry describe the kahuli as the singing snails of Hawaii.
Hawaiians also fashioned snail shell lei — at least one is believed to have been presented to Capt. James Cook when he arrived in the islands. And collecting the shells was all the rage in the late 1800s and early 1900s.
"They are like jewels on the trees," Sischo said of the snails. "They are so spectacular. You can see why people like to collect them."
Why are Hawaii’s snails going extinct?
It’s a sad story and almost everyone has an indirect hand in it.
The decline began centuries before western contact, when early Polynesian settlers cleared forests and introduced rats, which feasted on the snails and exiled them to the island’s mountain ranges.
The onslaught continued with each wave of human settlers and their introduced species. Deer, goats and pigs destroyed forest vegetation and fragmented snail populations. Jackson’s chameleons are known to devour the native snails, too.
Another villain is the rosy wolf snail, introduced as a biocontrol in the 1950s. The cannibal snail was brought to Hawaii by state agriculture officials in hopes of battling the giant African snail, which was imported to the islands as a potential food source but never won acceptance and escaped into the wild only to ravage agricultural fields.
Unfortunately, the rosy wolf snail bypassed the larger, tougher-skinned snails in favor of the delicate native Hawaiian snails.
"It’s a really depressing story," Sischo said. "Our little Hawaiian snails are like tasty snacks."
Unlike most snails elsewhere, which produce hundreds of offspring, Hawaiian snails give live birth to only a few offspring per year. This makes it impossible for them to keep up with the predators they face, he said.
Fighting back is a small but intrepid community of Hawaii snail conservationists, including members of the O‘ahu Army Natural Resources Program, the U.S. Fish and Wildlife Service and the University of Hawaii Hawaiian Tree Snail Conservation Lab, which rears endangered tree snails for release into the wild.
The Snail Extinction Prevention Program was created to help coordinate the various efforts. So far the work is focused on predator control, surveying for remnant populations, monitoring population changes and helping with field research, among other things.
While Sischo, a 30-year-old UH doctoral candidate, is the program’s only staff member, he just won a $250,000 grant to hire an assistant, add to its helicopter transportation fund and pay for more rat traps.
On a recent weekday, Sischo marched through the clouds and intermittent rain at the 2,000-foot level in the Waianae Mountains, searching for an isolated population of critically endangered Achatinella tree snails.
He found them clinging to the undersides of leaves in a four- or five-tree area of steep terrain. There was Achatinella concavospira, a species believed to have fewer than 200 individuals, and the Achatinella mustelina, a species known to exist throughout the Waianae range but still at risk of extinction.
There were also a few members of the Tornatellides species, a snail so tiny it can fit on the head of a pencil.
Twenty more minutes up the mountain revealed a specially designed exclosure — one of five such structures on Oahu. It is a place where rare snails can thrive free of predators like their ancestors millions of years ago.
No singing was heard on this day, however. Sischo said scientists believe the songs of the kahuli, which have no vocal organ, actually belong to crickets who live in the same habitat.
"Some say they don’t sing anymore because they’re sad they’re going extinct." he said. "Others say they just don’t sing for the scientists."
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