Kāhuli Tree Snails

Description

Kāhuli tree snails are tiny mollusks with colorful, elongated shells. The soft body of a snail has two parts: the foot and the head. The foot of the snail is the part of the body used for crawling. The head is where the tentacles (or stalks) attach and these contain sensory organs. Kāhuli tree snails are very small—their oblong shells are less than an inch (2.5 centimeters) in length. When young are born, they are less than a half-centimeter long.

Range

Kāhuli tree snails are endemic to Hawaii and are found only on the island of O‘ahu. Native trees and shrubs are the best habitat for kāhuli tree snails. Non-native predators, such as rats and Jackson’s chameleons, are the greatest threats to kāhuli tree snails. One of the worst predators is actually another snail—the carnivorous rosy wolf snail (Euglandina rosea). The rosy wolf snail was purposefully introduced in Hawaii with the hope that it would kill off the invasive giant African snail (Achatina fulica). Unfortunately the rosy wolf snail much prefers the bite-size kāhuli to the giant African snail, and the planned introduction ultimately backfired.

Diet

Kāhuli tree snails have adapted to a very specialized diet. They only eat fungus that grows on the leaves of trees and shrubs.

Life History

Kāhuli tree snails are hermaphrodites, meaning they have both male and female reproductive parts. They give birth to live young. Unlike many small organisms, kāhuli tree snails have long life spans. Some of these snails live for more than 10 years. They don’t reach reproductive maturity until they’re a few years old, and after that, they only give birth to about seven offspring a year.

Conservation

Kāhuli tree snails were once so plentiful in Hawaii that collectors used them to make lei. This led to the initial decline of the snails, but the biggest threat now is predation from non-native species. This problem is compounded by the fact that kāhuli tree snails are slow-growing and slow to reproduce, so they can’t replenish their numbers faster than they’re being eaten. All of the 42 kāhuli species in the genus Achatinella are either federally listed as endangered or extinct.

Fun Fact

Hawaiian folklore mentions the singing capabilities of kāhuli. In fact, a lesser known Hawaiian name for kāhuli tree snails is pūpū kani oe, which translates to “shell that sounds long.” The singing is only a myth, but kāhuli tree snails have been the inspiration for traditional Hawaiian chants called “mele.” One chant called “Kāhuli Aku” is about the snails calling to golden plovers to bring them water. Kāhuli Aku has been set to music and is a popular children’s song.

Sources

Decimation of Endemic Hawai'ian Tree Snails by Alien Predators, American Zoologist

Global Invasive Species Database, Invasive Species Specialist Group

Hawaiian Tree Snail Conservation Lab, University of Hawaii

Pacific Islands Fish and Wildlife Office, U.S. Fish & Wildlife Service

The Living World of Molluscs

University of California Museum of Paleontology