A new tool in the battle against non-native invasive rats offers hope to restoring native ecosystems on Mokapu Island. The U.S. Fish and Wildlife Service, Hawaii Department of Land and Natural Resources Division of Forestry and Wildlife, USDA APHIS Wildlife Services, and its cooperators have completed a rat eradication project on Mokapu Island, located off the north coast of Molokai.
Rats are known to have devastating effects on native ecosystems throughout the world. In Hawaii that effect is magnified due to the archipelagos isolation and unique flora and fauna - many found nowhere else in the world. On Mokapu Island, Polynesian rats (Rattus exulans) are known to kill and eat native seabirds and eat rare plants and their seeds. Removing the rats, an invasive non-native species, from Mokapu will greatly benefit the islands native species.
"This aerial application of the rodenticide diphacinone is the first of its kind for offshore islands in Hawaii," said Chris Swenson, Pacific Islands Coastal Program Coordinator for the U.S. Fish and Wildlife Service. "Similar rat eradication methods have been successfully used in other parts of the world since the early 1990s."Volcano Helicopters from Hilo was contracted to apply the fish-flavored, compressed cereal grain pellets containing 50 parts per million of diphacinone. Aerial applications using an MD 500E helicopter were carried out on February 6 and 12. This is the only safe and practical method of deploying rodenticide to areas as steep as Mokapu Island. Two applications were needed to ensure that the bait was evenly distributed throughout the and because it must be eaten multiple times over an extended period of time in order to be effective.
Prior to implementation of the project, public meetings were held on Molokai and an Environmental Assessment was completed in order to seek input from the public. Prior to the first aerial broadcast, a Hawaiian blessing for the project was performed by Molokai kpuna.
The will be monitored for rodents over the next two years, and if no rats are found up to that point, the eradication can be officially declared a success. Long-term monitoring of rare plants and seabirds will continue in order to measure the benefit to the native seabirds and plants. Monitoring on the will only cover the ridges and other safely accessible areas because of the island's steep and dangerous slopes.
Diphacinone was chosen as the active ingredient because it is safer than other compounds previously used; however, samples of water and marine organisms will be collected in nearshore areas that may have been exposed to the rodenticide. These samples will be tested for rodenticide residues and the results will be published in Molokai newspapers.
"The success of the Mokapu rat eradication project will provide natural resource managers throughout the state access to a proven method of bait application using a less toxic and more environmentally friendly rodenticide," said Peter Dunlevy, project manager for the eradication.
Three seabird species - wedge-tailed shearwaters (uau kani), red tailed tropicbirds (koae ula), and white-tailed tropicbirds (koae kea) are known to nest on Mokapu. The also has 11 of the last 14 Pittosporum halophilum (hoawa) plants in the wild and a small population of loulu lelo (Pritchardia hillebrandii) palms, which are becoming increasingly rare. The top threat to these offshore inhabitants is the rat.
Others involved in the project include the Molokai/Maui Invasive Species Committee and The Nature Conservancy on Molokai, Hacco Inc. and United Agriproducts.
Inquiries concerning the project can be directed to Chris Swenson, U.S. Fish and Wildlife Service at 808 792 9400, or Fern Duvall, Division of Forestry and Wildlife at 808 873 3502. Copies of the Environmental Assessment can be accessed through the U.S. Fish and Wildlife Services Pacific Island's website at: http://www.fws.gov/pacificislands/FinalEAMokapuRatEradication.pdf .The Department of Land and Natural Resources? Division of Forestry & Wildlife (DOFAW) is the largest land management entity in the State of Hawai?i with direct responsibility for management of approximately 944,500 acres of state trust lands. These lands include the state's forest reserve system, natural area reserve system, plant and wildlife refuges and wilderness and game management areas.
Note to Editors: Images are available by calling Ken Foote at (808) 792-9535.
