State and federal officials are developing a plan to expand the use of poison to eradicate and control rats and mice in native wildlife areas in Hawaii and other places in the Pacific.
Officials said they want to protect native plants and animals and find the best methods of eradication and control without affecting the native species.
“We’re looking at the safest and most efficient way to use (poison),” Earl Campbell, chief of the invasive species program for the Pacific Islands Fish and Wildlife Office, part of the U.S. Fish and Wildlife Service, said last month.
Mongooses and rodents have had a devastating effect on wildlife in Hawaii, especially native birds that nest on the ground, where they and their eggs are vulnerable.
The mongoose was introduced into Hawaii in 1883 to help control rats on sugar cane plantations, and is established on all islands but Kauai. A diurnal animal that failed to control the nocturnal rat population, it has contributed to the decline in ground-nesting birds like the Newell’s shearwater and nene goose.
Rodents, including the Polynesian rat and black rat, are considered the leading cause of the accelerated decline of Hawaii forest birds and the native forest itself.
Polynesian rats arrived in about A.D. 400, and the black and Norway rats came with Westerners in the 1780s.
Some rats, which can climb trees and swim more than a mile, compete with forest birds for food such as native snails, insects, seeds and fruits, wildlife officials say.
Black rats have been the primary cause in the decline of the endangered Oahu elepaio and also a decrease in palila hatchlings on Mauna Kea on Hawaii island, federal wildlife officials said.
A draft programmatic environmental impact statement looks at expanding the use of the rodenticide diphacinone.
The poison is now commonly used in bait stations that allow only select animals to enter and eat the bait. Officials are looking at using aerial drops as an alternative in inaccessible wildlife areas, where bait pellets would be dispersed from a bucket suspended by a helicopter.
Other methods of distribution under consideration include flinging pellets by hand or by mechanical spreader, and placing bait in a bag in the canopy of trees or shrubs.
State and federal officials hope to develop detailed strategies for controlling rodents as well as mongooses in about a year.
For now, officials have been holding a series of statewide meetings to receive public comment on the preliminary EIS that includes past uses of pesticides and various alternatives in controlling rodents and mongooses. More public meetings will be held once a draft environmental impact statement is prepared about a year from now, officials said.
Diphacinone, produced by Wisconsin-based Hacco Inc., has been used successfully in eliminating rats on Mokapu island near Molokai and Cocos island south of Guam, Campbell said.
According to one study included in the programmatic EIS, diphacinone did not result in deaths of Micronesian starlings on Cocos island, whereas another rodenticide did.
Campbell said wildlife officials are considering applying diphacinone aerially to Hanawi in East Maui, where rats are causing a decline in native birds.
He said a predator-proof fence in combination with diphacinone bait stations and mechanical traps at Kaena Point has prompted the return of native vegetation, as well as a rise in the number of albatrosses.
The deadline for public comment on the draft is April 7.
Comments may be made in the following ways:
>> Electronically at regulations.gov. Follow the instructions for submitting comments on Docket No. FWS-R1-ES-2015-0026.
>> By letter to Public Comments Processing, Attn: FWS-R1-ES-2015-0026; Division of Policy and Directives Management; U.S. Fish and Wildlife Service; MS: BPHC; 5275 Leesburg Pike; Falls Church, VA 22041–3803.
