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U.S. Army Protects Critically Endangered Hawaiian Snails from Invasive Predators

The views expressed are those of the author and are not necessarily those of Scientific American.

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Achatinella mustelinaThree hundred critically endangered kahuli tree snails (Achatinella mustelina) have a new home this week: a basketball court–size, predator-proof enclosure built for them by the U.S. Army in Hawaii’s Waianae Mountains.

The snails, according to the Army, spent the past two years in a lab at the University of Hawaii at Manoa while the new enclosure was built. The Army did not disclose the cost of the new habitat, but told the Associated Press it was built with the help of state and federal agencies.

Kahuli tree snails were once quite common in Hawaii, but the introduction of nonnative rats and other animals to the islands nearly wiped them out along with many other indigenous Hawaiian species. Rats apparently love to dine on the tiny snails, as does the Rosy wolfsnail (Euglandina rosea), aka the “cannibal snail,” which is known for eating other snail species.

The wolfsnail, which originates in tropical North American sites such as Florida, was introduced to Hawaii in 1955 in a misguided attempt to kill off another invader, the giant African land snail (Achatina fulica), which itself was eating valuable agricultural crops. African snails first appeared on the islands in 1936, possibly after hitching a ride on cargo ships. Unfortunately, wolfsnails balked at eating the bigger African snails and instead traveled to higher elevations, preying there on smaller Hawaiian snails, quickly driving as many as 20 species into extinction.

In addition to being prey, kahuli tree snails have an evolutionary factor against them. They are one of the rare snail species that produces live young, with just one baby snail produced at a time. Rosy wolfsnails, on the other hand, lay eggs, yielding as many as 600 young a year.

The Army has a long history of work to protect the kahuli tree snail and other wildlife. “The Army, as a federal agency, is required to protect threatened and endangered species found on its installations,” Kapua Kawelo, a biologist with the Oahu Army Natural Resource Program (OANRP), told ARMY.MIL in 2010. “On Oahu the Army is required to stabilize the population of the endangered Oahu tree snail.” She said that the snail is currently found in eight locations in the Waianae Mountains, with around 300 snails per location.

One of the Army’s efforts involved using trained dogs to track down wolfsnails. A pilot program with two dogs located nearly 1,000 of the cannibal invaders [note: a commenter, below, says the wolfsnails were actually found by humans, not the dogs]. Biologists with OANRP also maintain rat traps throughout the tree snails’ habitat.

Kahuli tree snails play an important role in Hawaiian cultural traditions. According to legend, the snails sing or whistle at night—although this has never been observed by scientists—and they are featured in several traditional songs, including a chant for Queen Kapi’olani, a 19th-century Hawaiian ruler.

[Correction: The species named in this article has been updated.]

Photo courtesy of the U.S. Department of Agriculture

John R. Platt About the Author: Twice a week, John Platt shines a light on endangered species from all over the globe, exploring not just why they are dying out but also what's being done to rescue them from oblivion. Follow on Twitter @johnrplatt.

The views expressed are those of the author and are not necessarily those of Scientific American.

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  1. 1. jgrosay 7:25 am 02/17/2012

    May I have read that snails arrived to the Hawaii islands from abroad, sometimes in such bizarre ways as in aircraft undercarriage bays, that in the islands there never was a native snail population, and that snails exterminated all local bird species by eating their eggs and pups, or this was in another island system ?

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  2. 2. John R. Platt in reply to John R. Platt 9:47 am 02/17/2012

    You’re mixing things up a little bit, J. Hawaii had a few dozen native snail species. Invasive snails came in on ships and airplanes and chowed down on Hawaiian snails and quite a few other species. Hawaii also has a long list of other invasive species (insects, snakes, pigs, etc.) that have done great damage to the islands’ ecology.

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  3. 3. j8055 7:15 pm 02/17/2012

    Achatinella sowerbyana is not the tree snail species being released in the exclosure on the Waianae Mountains. A. sowerbyana are only found in the Koolau Mountains.

    Achatinella mustelina is the species being released in the exclosure.

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  4. 4. stephjoe 5:01 am 02/18/2012

    As someone who works for OANRP, I have to correct a few of the author’s statements. First, as the previous person mentioned, the species being released was Achatinella mustelina. Also the statement “One of the Army’s efforts involved using trained dogs to track down wolfsnails. A pilot program with two dogs was quite successful, locating nearly 1,000 of the cannibal invaders.” This is incorrect, our dog program was not especially promising. For more information on the results of using dogs to detect Euglandina, please refer to Appendix 4-2 of our 2010 status report ( The 1,000 wolfsnails removed from the area were found and removed by staff, not dogs.

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  5. 5. John R. Platt in reply to John R. Platt 10:23 am 02/19/2012

    Thanks for your information. I have corrected the article.

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  6. 6. hi aloha 4:13 pm 02/19/2012

    Actually with the Army’s spread of depleted Uranium leeching into our aquifers, bombing practices, unexploded ordinances left all over the islands I find this article to be misleading.

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  7. 7. hi aloha 10:16 am 02/20/2012

    Here is a good example of how a little mitigation does nothing for the rest of the damage the military does to our land: ” ‎”U.S. Army officials say about 15,000 gallons of wastewater went into the water from a main under the Sand Island bridge, adjacent to the Marine Education & Training Center.”

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