Final Comprehensive Conservation Plan - U.S. Fish and Wildlife ...

4.12.7 Mollusks
Hakalau Forest National Wildlife Refuge
Comprehensive Conservation Plan
Over 70 nonnative snail species (Staples and Cowie 2001) and 12 nonnative slug species (Joe and
Daehler 2008) have been introduced to the Hawaiian Islands. Herbivorous mollusks can impact
native plants and agricultural crops. These mollusks can have a large impact on plant communities by
affecting seedling survival, shifting species abundances, and influencing succession. Invasive slug
herbivory can harm native plant outplantings and restoration efforts, thus requiring local control at
these sites (Joe and Daehler 2008). In addition, some nonnative mollusks prey on native land snails,
as well as compete with native species for limited resources (Staples and Cowie 2001). Slugs have
been seen girdling endangered plant seedlings and saplings and feeding on endangered plant flowers
and fruit (Jeffrey, pers. comm.).
One nonnative land snail and three nonnative slugs were found at the HFU during invertebrate
surveys. The garlic snail was abundant, especially in the Hakalau Tract, and may be a competitor for
native birds and a predator to other native snails. Arion intermedius (glade slug) was also very
common. These species were more abundant in areas disturbed by pigs (Howarth et al. 2003).
4.13 Special Designation Areas
The staff conducted a wilderness review (Appendix D), the results of which indicate that the HFU
contains resources and lands that meet the basic criteria for inclusion in the National Wilderness
Preservation System. The lower elevations of Hakalau Forest NWR will be designated as a
Wilderness Study Area and additional information will be gathered and evaluated before a final
determination is made (see Appendix D). The Service will make final wilderness recommendations
for all Hawaiian and Pacific Island NWRs after the CCPs for all refuges have been completed.
4.14 References
Ahumada, J.A., D. LaPointe, and M.D. Samuel. 2004. Modeling the population dynamics of Culex
quinquefasciatus (Diptera: Culicidae), along an elevational gradient in Hawaii. Journal of Medical
Entomology 41(6):1157-1170.
American Bird Conservancy. 2004. "Managed" cat colonies: the wrong solution to a tragic problem.
Available at: http://www.abcbirds.org/abcprograms/policy/cats/materials/colonies.pdf. Accessed
April 21, 2008.
Anderson, S., J., C. P. Stone, and P. Higashino, K. 1992. Distribution and spread of nonnative plants
in Kipahulu Valley, Haleakala National Park, above 2,300 feet elevation. In: C.P. Stone, C.W. Smith,
and J.T. Tunison (eds.), Alien Plant Invasions in Native Ecosystems of Hawaii: Management and
Research. Cooperative National Park Resources Studies Unit, University of Hawaii, Honolulu. 887
pages.
Atkinson, I.A.E. 1977. A reassessment of factors, particularly Rattus rattus L., that influenced the
decline of endemic forest birds in the Hawaiian Islands. Pacific Science 31:109-133.
Chapter 4. Refuge Biology and Habitats 4-109