Tree & Land Snails / Akaleha'
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Tree & Land Snails / Akaleha'
Native Tree Snails
Partula radiolata (Photo by barry Smith)
There are 66 species of native terrestrial snails on Guam. Snails that live on vegetation are referred to as tree snails, while those that burrow under decaying leaves and soil are called land snails. All are known as "akaleha' " in Chamoru. All evolved in isolation from many of the predators and parasites found in continental areas. The tree snails had so few enemies that they no longer needed to reproduce prolifically and evolved to have only a few young at a time and to take one to several years to reach maturity. On Guam, all of them are now rare, endangered, or extinct.
Several factors work in combination to threaten the tree snails, including habitat loss to agriculture and development, pesticides, wildland fires, competition from introduced species, and predation by a large introduced flatworm (Platydemus manokwari).
At least one species of tree snail, the endemic Partula salifana, and two species of land snails are now extinct on Guam. All of Saipan's tree snails and two of Rota's three species are also extinct.
Introduced Species
[Giant African snail photo]
A number of introduced snails also occur on Guam, the most well known being the giant African snail. Also known locally as "akaleha' ", they came to Guam during World War II, perhaps by hiding aboard a cargo ship. Some biologists think they were deliberately brought here for people to eat.
The giant African snail is still found at many locations around the island. However, it is much less common today than in the 1960s and 1970s, when it became an agricultural pest. Its numbers are probably controlled by the flatworm. This snail grows quickly and can reach full size in two years. Some snails over seven inches long have been found, but most are about three inches. The adults lay hundreds of eggs in loose soil and under leaves.
The flatworm, known as "tagulan tåno'" in Chamoru, is a voracious snail predator. It is 1-3 inches (2.5-7.5 cm) long and is nocturnal. During the day, it hides in leaf litter, and under logs and rocks. Its impact on native snails is similar to that of the brown tree snake on Guam's bird populations. The intentional introduction of the flatworm to other Pacific islands should be discouraged.
Guam Comprehensive Wildlife Conservation Strategy, 9/27/2005
