Based on the field notes of a former Bishop Museum researcher, I have been hiking up and down a series of adjacent ridges and valleys in the Koolau Mountains to look for critically endangered species of kahuli or Oahu Tree Snails.
Since these generally nocturnal snails are often active in the early hours of the morning when moisture covers the vegetation, I would often start hiking an hour before first light on days when clouds shrouded the mountain-tops. Clouds create ideal conditions to see active snails for the sunlight they block and the moisture they bring.
Clouds repeatedly roll-in, condense on the vegetation as dew, and then blow-out on the ridge tops and hanging valleys of the Koolau Mountains.
After multiple attempts without success, I nearly fell over with excitement when I saw a cute little kahuli with a strikingly beautiful shell on an ohia shrub. The shell was about a half-an-inch long and was dark green at the base with brown, yellow, and caramel stripes that spiraled up the spire. Also known as “pupukanioe” or “pupu kuahiwi” in Hawaiian, these tree snails graze on algae and fungi that grow on the surface of leaves.
While I photographed the snail, the clouds began to dissipate and the rays of the sun bathed the landscape in sunlight. As a result, the snail crawled to the underside of the leaves, retracted into its shell, and went to sleep for the day. For the next two hours I searched every shrub in the immediate area to see if I could find another specimen but was unable to find another snail.
Research at Bishop Museum revealed that this species of Oahu Tree Snail is Achatinella abbreviata. When I told Kenji Suzuki what I found, he told me that A. abbreviata is thought to be extinct with the last individual seen in the 1960’s. When I further told him I was unable to refind the snail on two subsequent trips to the same shrub, Kenji recruited some of the sharpest-eyed snail aficionados on the island — Joel Lau, and Jim and Yuko Johnston — to help confirm the discovery.
After the five of us climbed-up the steep cloud-covered mountain, we looked on the same shrub and all the plants within a fifty foot radius to look for A. abbreviata. I am sad to report that our efforts to search the foliage with a fine-toothed comb were unsuccessful.
Our worst fears were realized when we found a carnivorous wolf snail (Euglandina rosea) about an inch-and-a-quarter long on a neighboring ohia shrub. I suspect that this carnivorous snail may have hunted-down, killed and eaten the cute little A. abbreviata I previously photographed.
The plight of the Oahu Tree Snail is a woeful tale. The snails have been in decline for well over a hundred fifty years. A shell collecting craze in the in the late 1800’s and early 1900’s decimated their numbers, and whatever snails survived the collecting onslaught have been heavily preyed upon by rats and carnivorous snails. Without conservation measures to protect these precious little creatures, there is nothing to stop their ultimate demise.
Hawaii’s Extinct Species — Snails, Bishop Museum
Mass Extinction of Hawaiian Land Snails, AAAS Pacific Division
Oahu Tree Snails Found on Oahu, Pamphlet by Ken (Kenji) Suzuki
Recovery Plan for the Oahu Tree Snails of the Genus Achatinella, US Department of the Interior, Fish and Wildlife Service, Region One, Portland Oregon, June 1992