|Barbara A. Maxfield
Chief, Division of External Affairs
Pacific Islands Ecoregion
U.S. Fish and Wildlife Service
300 Ala Moana Blvd., Room 3-122
Honolulu, HI 96850
Public Outreach Coordinator
Hawaiian Islands Humpback Whale National Marine Sanctuary
Hawai‘i Department of Land and Natural Resources
Tel: (808)587-0365 Fax:(808)587-0115
1151 Punchbowl St.
Honolulu, Hawaii 96813
Kure Atoll Now Rat-Free After Multi Year Eradication
After seven years of hard work and monitoring to control Polynesian rats (Rattus exulans) on Kure Atoll's Green Island, Hawaii Department of Land and Natural Resources (DLNR) wildlife officials have finally declared the 260 acre island, "rat-free."
Rats trapped on Kure Atoll
Kure atoll is a State of Hawaii Wildlife Sanctuary dedicated to protecting the numerous seabird and shorebird populations which breed, visit, or migrate to the island each year. For decades, the island has been challenged by the rat population that has wreaked havoc on the nests, eggs and chicks of the many ground-nesting seabirds, boobies, shearwaters, petrels, tropicbirds, terns and noddies that breed on the island.
The multi-year eradication effort began in 1993 as a joint effort of DLNR and the U.S. Department of Agriculture. Wildlife biologists who instituted the program say follow up assessments have shown that for nearly 6 years now there has been no sign of rat activity on the island, indicating that the eradication efforts proved successful.
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According to Ethan Shiinoki, DLNR wildlife staffer (above), "With the reduction in the rat population, there has been a marked increase in the numbers of Christmas shearwaters, Bonin Petrels, Wedge-tailed Shearwaters, and Red-tailed tropic birds. Although these bird species are not presently endangered, their range throughout the Hawaiian Islands, especially the main Hawaiian Islands, has been vastly reduced due to predators like rats."
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Polynesian rats were most likely introduced by accident to Kure by early Polynesians who visited the island. However, the rats may have also been spread by boat traffic, shipwrecks or with floating debris. The rats may have been abundant on Green Island since at least 1870 and have been the most significant predator at Kure. By the mid 1960's, large numbers of birds, their chicks and eggs, had been decimated.
The Kure Atoll rat control program was initiated in August 1993 with the goal of total eradication. During the initial phase of the program, three-hundred bait stations were installed throughout the island. Very quickly, the rats were eliminated down to a 4% detection level. Baited stations were left in place when the Coast Guard left the island permanently the following month. This initial phase of the program was supervised by the U.S. Department of Agriculture Animal Damage Control Branch, with manpower and oversight supplied by DLNR's Division of Forestry and Wildlife.
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In February of 1994, DLNR and the National Marine Fisheries Service returned to the island to re-bait and monitor the stations. At that time detection of rats was less than 5%. In May of 1995, 400 "gnaw" sticks (wooden staked soaked in peanut oil and driven into the ground with 8 inches protruding - see above), 100 bait stations and 400 pounds of rat bait with diphazinone were delivered to Green Island. One DLNR wildlife technician remained on island until July to assess rat activity. Each bait station was checked three times during that period. For the first time, no rat activity was witnessed.
A year and a half later, in September of 1995, the island was checked again. Instead of finding rats in the bait stations (see below), wildlife staff found geckos and large black beetles in and around the stations. These animals are typically prime rat food, which again indicated to the biologists that rats had been eliminated.
Just to be sure, subsequent surveys have been conducted annually (1996-2000). During those follow-up surveys, wildlife officials checked bird carcasses and vegetation for signs of rat predation or scavenging. The latest survey was done this past summer when Ethan Shiinoki, DLNR wildlife staffer again found no sign of rat activity.
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"Rats appear to be eliminated on the island, at least for now," said Shiinoki. As a result, we expect our bird populations to continue to climb. However, rats could reappear again via another shipwreck or accidental introduction during an illegal access.
"It's critical that this island remain isolated from human impacts. Any re-introduction of rats or other predators to this island would have a devastating impact on the ground nesting seabird populations that are now on the rebound," Shiinoki continued.
"This is a great success story for us and we hope that we can keep the island rat-free. The success of the rat control program at Kure shows that resource management agencies in Hawaii have the technology and expertise to conduct successful predator control programs," said Shiinoki.
"With one major problem dealt with, we can now turn our attention to weed control, another major management problem of us on island," concluded Shiinoki.
Shiinoki and fellow wildlife staffer Nalu Yen will continue to check for rats during their current visit to the island this week. They have been on island for 2 days now and have not seen any sign of rat activity. Throughout the week, they will continue to monitor the island for rats and other management issues that challenge the bird, turtle and monk seal populations at the Atoll.
Kure Atoll is located 1,175 nautical miles northwest of Honolulu at the extreme northwestern end of the Hawaiian Archipelago. The island is 60 nautical miles west-northwest of Midway Atoll. Kure is the northernmost coral atoll in the world. It's largest emerged island, Green Island is home to 16 species of nesting seabirds and serves as a wintering area for a variety of migratory bird species from North America and Asia.
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