CHAPTER 1 - Guam Buildup EIS

Guam and CNMI Military Relocation Final EIS (July 2010)
Common Name: Humped tree snail, Mariana Islands tree snail
Chamorro Name: Akaleha’
Scientific Name: Partula gibba
SPECIES DESCRIPTION
Named for the enlarged last whorl of its shell forming a ―hump‖. The shell is a conical shape, and has four to
four and a half whorls. Primary shell color is chestnut brown to whitish yellow, and occasionally purple. All
forms are accented by white or brown lines along the suture between shell whorls. (1)
LISTING STATUS
A federal candidate for Endangered Species Act listing. (2) Listed as critically endangered globally by the
IUCN. (3) In Guam, considered a Species of Greatest Conservation Need. (4)
THREATS
Threats include habitat degradation and removal, predation by native and introduced flatworms and other
snails, and typhoons negatively impacting the forest. (1)
ECOLOGY
Preferred habitat is cool, shaded forest with high humidity. These snails also prefer subcanopy vegetation.
Diet consists of decaying material, and foraging occurs primarily at night. Life history includes
hermaphroditism, with reproduction occurring within the first year of life. Lifespan is thought to be up to five
years. This species gives birth to live young. (1)
HISTORICAL AND CURRENT DISTRIBUTION
Found historically on Guam and numerous islands within the CNMI including Rota, Aguiguan, Tinian,
Saipan, Anatahan, Sarigan, Alamagan, and Pagan. At present, found in the areas listed above, with the
exception of Tinian and Anatahan, where the species is thought to be extirpated. (1)
REFERENCES
1. USFWS. 2008. Species Assessment and Listing Priority Assignment Form: Humped Tree Snail (Partula
gibba). Portland, OR.
2. USFWS. 2008. Endangered and threatened wildlife and plants; review of native species that are candidates
for listing as endangered and threatened; annual notice of findings on resubmitted petitions; annual
description of progress on listing actions. Federal Register 73:75175-75244.
3. Mollusc Specialist Group. 1996. Partula gibba. In IUCN Red List of Threatened Species. Version 2009.1.
www.iucnredlist.org.
4. GDAWR. 2006. Guam Comprehensive Wildlife Conservation Strategy (GCWCS). Department of
Agriculture, Guam. 7 November.
Photo: http://www2.hawaii.edu/~capers/PacEco/wesa/pacSnails.html.
VOLUME 9: APPENDICES G-2-8 EIS Resource Technical Appendix