Kāhuli Tree Snails
Scientific Name: Achatinella spp.
Description: Kāhuli tree snails are tiny mollusks with colorful, elongated shells. Their closest terrestrial relatives are other snails and slugs. The soft-body of a snail 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. As would be expected, the head is also where the snail’s mouth is located.
Size: Kāhuli tree snails are very small--their oblong shells are less than an inch in length. When young are born, they are less than half a centimeter long!
Diet: Kāhuli tree snails have adapted to a very specialized diet. They only eat fungus that grows on the leaves of trees and shrubs.
Predation: Nonnative 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 Hawai‘i 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.
Habitat: Native trees and shrubs are the best habitat for kāhuli tree snails.
Range: Kāhuli tree snails are endemic, or unique, to Hawai‘i, and are found only on the island of O‘ahu.
Life History and Reproduction: Kāhuli tree snails are hermaphrodites, meaning that 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 over 10 years! They don’t reach reproductive maturity until they’re a few years old, and after that, they only give birth to about 7 offspring per year.
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!
Conservation Status: Kāhuli tree snails were once so plentiful in Hawai‘i that collectors used them to make lei. This led to the initial decline of the snails, but the biggest threat right now is predation from nonnative 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 (group) Achatinella are either federally listed as endangered or extinct.
Decimation of Endemic Hawai'ian Tree Snails by Alien Predators
Fish and Wildlife Service Pacific Islands Office
Global Invasive Species Database
Hawaiian Tree Snail Conservation Lab
The Living World of Molluscs
University of California Museum of Paleontology