Black Rats Take the Bait on Palmyra Atoll
Biologists claim victory over rodents on Palmyra Atoll in an ongoing effort to restore seabird populations, this time in the tropics.
In a precedent-setting project for tropical restoration, invasive black rats that had been preying on native animals on a remote Pacific atoll were successfully eradicated this summer.
"Although it will be two years before we can confirm rat removal, the operations were a great achievement," said Susan White of the U.S. Fish and Wildlife Service, who oversaw the operation on Palmyra Atoll.
She explained how crews from several government agencies and nonprofit groups dropped poison by plane on Palmyra in June; spread it on the ground by hand and shot it by slingshot into palm trees overhanging the water. By August, there were no signs of rats on this "complex and challenging environment," White said.
The largely unoccupied group of 25 islets, a national wildlife refuge in the Pacific Remote Islands Marine National Monument, is located about 1,000 miles south of Honolulu.
Most island eradications — including rat projects on Anacapa Island in the Channel Islands National Park off Southern California and on Rat Island in the Alaska Maritime National Wildlife Refuge — take place in temperate zones. On Palmyra, White said, eradication crews had to cope with dense rainforest vegetation, and they had to find a rat poison that would work when wet.
The crews also faced the daunting task of capturing and caring for the native bristle-thighed curlews, which are large shorebirds with long, curved bills. The birds need 24-hour care in captivity: Every few hours, their legs must be manually stroked and moved around to maintain their circulation. Project crews captured 13 curlews and set up a round-the-clock schedule of physical therapy for them from early June to early August, when they were released. Since then, eight of the birds have been spotted with non-captured flocks.
"People said it couldn't be done, but we did it," White said. "The team was phenomenal in their tenacity and dedication in capturing the curlews and keeping them from getting stressed."
In addition, she said, the atoll's native geckos were successfully captured and released back to their respective islets.
"The lessons learned from removing invasive rats from Palmyra Atoll are critical to the survival of seabirds and native species on islands around the world," said Bill Waldman, executive director of Island Conservation. "Following upon successful projects in temperate climates, … the methods developed for and proven at Palmyra set a precedent for subsequent efforts to restore other tropical islands, protecting species in places where it might have seemed impossible before."
As Miller-McCune reported in 2009, island restoration is a primitive science, subject to unforeseen consequences. Fish and Wildlife and The Nature Conservancy, an international nonprofit organization, maintain a small research station on Palmyra that provides information about how healthy ecosystems respond to invasive species, climate change and marine restoration. Island Conservation, a nonprofit group based in Santa Cruz, Calif., participated in the rat eradication with them, along with members of the U.S. Department of Agriculture and U.S. Geological Survey.
Black rats were likely introduced to Palmyra during U.S. military occupation of the atoll in World War II. According to Island Conservation, the rats preyed on ground-nesting and tree-nesting birds, particularly sooty and white terns, consuming their eggs and chicks; they attacked native land crabs, and they ate the seeds and seedlings of native trees. Several species of seabirds, including burrow-nesting shearwaters and petrels, no longer breed on Palmyra.
The incongruity of environmentalists killing animals in order to save others on the Channel Islands was the basis of novelist T.C. Boyle's most recent book, When the Killing's Done. In a conversation with Miller-McCune's Tom Jacobs, Boyle discussed how characters in his novel grapple with the inherent contradictions:
"They believe in preserving wildlife and the environment. But they disagree on this essential question. Dave believes all life is sacred. Alma agrees, but she believes in making exceptions for practical considerations, such as killing pigs and rats to save indigenous species that are unique to this island, and are on the verge of extinction. You must sacrifice (some life for this greater good). That's what this debate is about."