By Jan TenBruggencate

The tree snails are Hawaii's arboreal gems. Gorgeous creatures, they are much more reminiscent of colorful seashells than the snails we know from the land. Their shells come in diverse patterns of ivories and whites, browns and yellows and tans.

And they are fadingly rare. Where O'ahu residents once collected bags full of the wonderfully patterned snails in forests near residential areas, most species are now extinct or rare.

The Big Island tree snail, Partulina physa, was believed gone until a small population was found at Pūpū Kani Oe on Ponoholo Ranch in Kohala. The 96-acre site gets its name from the “singing snails.” Hawaiian tree snails were believed to be the singers responsible for melodies floating through the forests.

Only Population in the World

“This is the only population in the whole world,” said Jon Giffin, The Nature Conservancy’s Hawai‘i Island field representative. “This small parcel and an adjacent parcel support the entire known population of the pūpū kani oe tree snail.”

Ranch owner Pono von Holt has now signed a 15-year conservation agreement with The Nature Conservancy of Hawai'i, to help protect the 'ōhi'a-dwelling snails.

The Pūpū Kani Oe site is along the rim of Honokane Valley, in forested land that has been degraded by wild cattle and pigs. It lies at elevations from 3,400 to 3,800 feet, with rainfall of more than 100 inches annually.

The area provides habitat for common native forest birds such as the ‘apapane, ‘amakihi and ‘elepaio. The Hawaiian owl, or pueo, and the endangered Hawaiian hawk, ‘io, have been seen here, while the endangered Hawaiian duck, koloa, utilizes nearby streams for feeding and resting.

Partnership Tackles Forest Threats

“Vegetation on the parcel has been severely degraded by wild cattle and feral pigs, but the necessary forest structure (trees, shrubs, herbs and epiphytes) is in place to allow the native forest to regenerate naturally once the threats are removed,” Giffin said.

Von Holt put the land into the Kohala Watershed Partnership five years ago, and the partnership has already done some fencing and other work. However funding cuts limit how much more work can be done. The Nature Conservancy help move the protection program forward.

“We will support the partnership with any of its ongoing work. But what we are going to be doing that they are not doing is baseline biological surveys to see what native resources are up there. We are also going to draft a management plan for the 96 acres. That management plan will be centered on protection of the tree snails,” Giffin said.

Among the possible threats, beyond habitat degradation by pigs and cattle, are rats and the cannibal snail Euglandina rosea.

Von Holt said his conservation agreement makes sense not just for the singing snail, but also for the ranch itself.

“The conservation management agreement will enhance our ability to practice good land stewardship by combining Ponoholo Ranch resources with the expertise, experience, and resources of The Nature Conservancy. The restoration of native forest in the Pūpū Kani Oe parcel will benefit the watershed of the Kohala Mountain, the livestock entities that depend on it, and the community of Kohala,” von Holt said.

Jan TenBruggencate is an award-winning journalist and former science and environment for The Honolulu Advertiser who lives on Kaua'i and writes on environmental topics in his Raising Islands blog.

Nature picture credits (top to bottom, left to right): Photo © Bill Mull (Partulina physa); © Melora Purell/Kohala Watershed Partnership (Partulina physa on 'ōhi'a lehua leaves).