MARIANA ISLANDS RANGE COMPLEX ... - Guam Legislature

MARIANA ISLANDS RANGE COMPLEX FEIS/OEIS MAY 2010
Life History and Ecology. Like the other Partulid snails, the humped tree snail prefers to live on subcanopy
vegetation in lower forest strata and is not found in the high forest canopy. The conditions
favorable to Partulid snails are only found in intact limestone forests, mesic coastal strand vegetation, and
forested river corridors.
Little is known about the breeding ecology of the Partulid tree snails of the Mariana Islands. Similar
Partulid species, however, suggest that tree snails in the Marianas are hermaphroditic, like all other
terrestrial pulmonate snails. In general, Partulids begin reproducing in less than 12 months, and may live
as long as five years. Up to 18 young are produced each year. While most terrestrial pulmonate snails lay
eggs, the Partulids give birth to fully developed young. The snails are generally nocturnal, living on
bushes or trees and feeding on decaying plant material.
Population Status and Distribution. The humped tree snail is the most widely distributed tree snail in
the Marianas Islands, and is known from Guam, Rota, Saipan, Tinian, Aguijan, Anatahan, Sarigan,
Alamagan, and Pagan. The snail was once thought to be the most common tree snail on Guam. Now,
however, the humped tree snail is considered extremely rare across its range (Hopper and Smith 1992),
numbering under 2,600 individuals (USFWS 2005c). On Guam and Rota, the humped tree snail has gone
from being widely distributed and super abundant to being highly localized and rare. All current
populations on Guam are found on the Guam intact forests of the Naval Munitions Site, and probably
number less than 1,000 individuals (USFWS 2005c). The same number of snails probably persists on
Rota (USFWS 2005c). Because of the abundance of a predatory flat worm, coupled with land use before,
during, and after World War II, in addition to intense warfare during the U.S. landings on Tinian, humped
tree snails are thought to be extirpated from Tinian (USFWS 2005c). A small population (