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Oahu Tree Snails

A brown and yellow snail on a green leaf.

Over 750 species of terrestrial snails were once described from the Hawaiian Islands, representing one of the most stunning examples of species radiations in the world.  Sadly it is estimated that over 90% of this diversity has been lost. In Hawaiian oral history, the snails are known to sing as they travel up and down the trees. Though their voices may have grown dim, we are still working to keep their song alive.

 

  • Scientific name: Achatinella spp 
    Hawaiian name: Kāhuli / Pūpū kani oe

    All 41 species of the genus Achatinella, also known as the O‘ahu tree snails, are federally listed as endangered. O‘ahu tree snails are diverse in patterns, colors, and shapes but all average about 3/4 inch in length. Most have smooth, glossy, and oblong or ovate shells with a variety of colors, including yellow, orange, red, brown, green, gray, black, and white. The entire genus is endemic to O‘ahu. Of those, 22 species are believed to be extinct and 18 are near extinction.

    View species listing and recovery documents on the Achatinella ECOS Species Profile.

    Habitat and Range

    Currently, O‘ahu tree snails are restricted to remnant native forest on the highest ridges of the Ko‘olau and Wai‘anae ranges on the island of O‘ahu.  Historically, the genus was widely distributed from near sea level along the windward coast to the central plains and throughout the Ko‘olau and Wai‘anae mountains. 

    Diet and life cycle

    O‘ahu tree snails are nocturnal and graze on a fungus that grows on the leaves of native plants. During the day they seal themselves up against leaves or tree trunks. Although native snails are sometimes found on non-native plants it is not known if the fungus on these introduced species is sufficient to support healthy populations. Adult snails are hermaphroditic and long-lived. Their life span is thought be at least 11 years, although growth rates and reproductive rates are very low.  The snails give birth to live young, and can reproduce anywhere from 4 to seven times a year.

    Past & Present:

    O‘ahu tree snails were once so abundant and popular on the island, they are mentioned in Hawaiian folklore and songs, and their shells were used in lei and other ornaments. These species occurred from near sea level along the windward coast, through the uppermost reaches of the Ko‘olau and Waianae Mountains and across the central plain.

    Historically, collectors played a very large part in the decline of the species. Destruction of native forest habitat and the introduction of predators such as rats and alien snails are probably the major reasons for reductions in the species' range and abundance. More recently, predation by the introduced carnivorous snail Euglandina rosea and the flatform Platydemus manokwari have decimated populations of the O‘ahu tree snails.

    Current threats include the continued degradation of habitat by non-native, invasive vegetation, especially strawberry guava (Psidium cattleianum), Christmas berry (Schinus terebinthifolius), silk oak (Grevillea banksii), shrub verbena (Lantana camara), and Koster’s curse (Clidemia hirta). 

    Pigs (Sus scrofa) also degrade habitat and predation by rats and introduced snails continues to be a problem. Low reproductive rates and limited dispersal abilities increase the vulnerability of this genus.

    Conservation Efforts

    Inside two unassuming trailers off the Pali Highway on the island of O‘ahu, scientists with HawaiÊ»i’s Department of Land and Natural Resources are fighting to save the Oahu tree snails. The trailers are home to the Hawai‘i Invertebrate Program run by Cynthia King and the Snail Extinction Prevention Program run by David Sischo.

    David Sischo and Cynthia King were recognized as 2017 Recovery Champions.

    The programs, which are partly funded by the U. S. Fish and Wildlife Service not only work to protect current populations and key breeding habitats, but also to establish additional populations, thereby reducing the risk of extinction. 

    Prior to the creation of SEPP, the majority of efforts focused on monitoring the decline of species; since the creation of SEPP, they have begun to halt species loss and actually improve the status of the snails. 

    Conserving and recovering Hawaii’s native and endangered species requires partnerships and dedication. Together with the state of Hawai‘i, the U. S. Fish and Wildlife Service is helping to ensure that the voices of the forest continue to sing in Hawai‘i

     

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