For over two years now I have been exploring a number of ridges and gullies in the Wai’anae Mountains to look for native snails many of which are extremely rare if not endangered.
The island of O’ahu is formed by two mountain ranges — the Wai’anae and Ko’olau Mountains — which run roughly parallel to each other in a northwest to southeast direction. With its highest point at 4,025 foot Mount Ka’ala, the Wai’anae Mountains are higher and older than the Ko’olau Mountains. Since the trade winds blow from a northeasterly direction, much of the Wai’anae Mountains lie in the rain shadow of the Ko’olau Mountains. Accordingly, the Waianae Mountains are drier and have a broader range of ecosystems making them more biologically diverse than the Ko’olau Mountains.
Much of my explorations in the Waianae Mountains have been made with Daniel Chung, PhD, a snail expert affiliated with the Bishop Museum and Kapiolani Community College. He is also well versed in native plants and is one of my sources of knowledge about native snails and plants.
Like the rest of Oahu, the Wai’anae Mountains have been over-run with invasive plants like strawberry guava, clidemia, and christmas berry. Since native snails are more often than not found in and around native plants we look in remote out-of-the-way places where remnants of native forests can still be found.
The rarest species are never found right on the trail and require explorations through the undergrowth which involve ducking under low tree branches, crawling through vines, and climbing over other obstructions.
While researching for the centennial of the Hawaiian Trail and Mountain Club (HTMC) I learned that Charles Montague Cooke, Jr. (1874–1948), was one of the charter members of the club. C.M. Cooke Jr. was the grandson of Amos Cooke who co-founded Castle and Cooke, and the son of Charles Montague Cooke who founded Bank of Honolulu. But unlike his father and grandfather, C.M. Cooke Jr’s interests lay in science — specifically in the field of malacology — the study of molluscs. In 1902, C.M. Cooke Jr. beame Curator of Pulmonata at the Bishop Museum where he collected, identified and classified Hawaiian land snails. In 1915 C.M. Cooke Jr. co-authored Volumes 23 – 25 of the Manual of Conchology with Henry Pilsbry — the authoritative reference on native Hawaiian snails even today.
The Hawaiian Islands are home to about 500 species of endemic land snails — more than half of which are extinct or on the verge of extinction. Pupu kuahiwi is “mountain shell” in Hawaiian and is the generic name for land snails. This white pupu kuahiwi (Auricullela ambusta) is endemic to the Hawaiian Islands and is a little longer than a quarter inch long.
Another endemic pupu kuahiwi, with flat round shells no more than a quarter inch long — Philonesia spp. — can also be found in ‘ie’ie (Freycinetia arborea). These snails are arboreal — live in the trees — and graze on algae and fungi that live on their leaves, stems, and branches.
The whorls of ‘ie’ie often retain catch and retain moisture from passing rain clouds. One of the more intriguing things you can sometimes find within them are a gelatinous clear substance which are the eggs of succinea snails.
Known by the much more memorable name “snot in a hat”, these endemic succinea snails (Succinea catinella rotundata) are the most common native snail today.
Native land snails can be found on talus slopes made from the shards of broken rock at the base of cliffs especially when the slope is wet and shady.
Small endemic land snails (Leptachatina crystallina) about a quarter inch long can be found on the underside of rocks and feed on decaying leaves.
Other rare snails are found at higher elevations above 2,500 feet where the moisture in clouds condense on the vegetation and provide additional water. Many snails require a regular dousing by water and cannot survive prolonged periods of drought.
Tornatellinid snails are so tiny — about 2 millimeters long — that I needed to screw in an additional lense at the end of my 100 mm macro lense to photograph them up close. Millions of these tiny snails used to live in the forest, but today their numbers are but a fraction of what they used to be.
The north-facing side of ridges often receive more rainfall. When they are shaded by vegetation which allows more moisture to be retained they can especially good for harboring rare native plants and snails.
Isolated populations of endangered kahuli (Achatinella mustellina) can still be be found in native olopua trees (Nestigis sanwichensis). This tree snail has a dark plaid pattern on its shell and is just under three-quarters of an inch long. The snails are mostly nocturnal and sleep on the underside of leaves during the day. Also known as “pupu kani oe” or “the shell that sounds long”, these are the snails that “sing”, ‘whistle”, or “chirp” according to Hawaiian oral tradition although science disputes this claim.
Here is a first hand account of Achatinella snails chirping by Tom McGuire during the 1895-1899 time period when he explored the mountains over Oahu and collected Achatinella snail shells in his youth. He was also a forester with the Territory of Hawaii and a kahuna lapa-au (traditional Hawaiian herbal doctor).
There is wide variation in the color and markings on Achatinella mustellina. This beige colored snail sleeps on the underside of beautiful olomea leaves (Perotettia sanwichensis) which have striking red veins and stems. Because of their great beauty a shell collecting craze swept the islands in the late 1800’s and early 1900’s.
Back in the 1800’s, Achatinella snails were so plentiful that it was inconceivable that they could go extinct. It is said that when you shook a tree in the mountains it would rain shells. A number of HTMC charter members in addition to C.M. Cooke, Jr. and Tom McGuire were avid shell collectors. Herman Lemke (HTMC charter member) had a shell collection of over 10,000 shells (part of which resides at the Waialae Country Club), as did Lorrin A. Thuston (HTMC’s 1st Vice President), and William R. Castle (HTMC’s 1st President). Unfortunately, shell collecting took a serious toll on the species. Of the 41 species of Achatinella snails, over two-thirds of them are extinct today. Only about a dozen species remain today and all of them are endangered.
Some of the rarest snails are sanguine litter snails (Laminella sanguinea). The shells of these snails are red with a pattern of zig-zag lines. The larger shell is half-an-inch long and the smaller shell is just over a quarter-inch long. Sanguine litter snails are extremely rare — since 2000, fewer than 30 living snails have been sighted.
Perhaps one of the rarest of the pupu kuahiwi is this endemic snail in the Cookeconcha genus, which is named after C.M. Cooke Jr. Believed to have descend from an ancient line of mollusks, these snails are a little more than a quarter inch long and have ribbed shells.
One of the great threats to native snails that remain today is the carnivorous wolf snail (Euglandina rosea) which was introduced from Florida to Hawaii to control the African snail population. But it was found that these large snails prefer to prey on native snails. Combined with predation by rats, habitat loss from invasive plants, and extended periods of drought, the outlook for native snails is not certain. While small pockets exist in the Waianae Mountains where native snails can still be found their future is not secure and additional conservation measures are needed to ensure their survival.
Charles Montague Cooke, Jr., Wikipedia
Hawaii’s Endangered and Threatened Species, Bishop Museum
Laminella sanguinea, Wikipedia
Manual of Conchology, Second Series: Pulminata, Vol 23, by Henry Pilsbry, ScD. and C. Montague Cooke, Ph.D., Academy of Natural Scienses of Philadelphia, 1915-1916
Native Hawaiian Plants, University of Hawaii, Department of Botany
Some Pacific Scientists I have Known, Edwin H. Bryan Jr., Bishop Museum Ocasional Paper XXIV