|
|
||
|
Search Archive | |
 |
 Anacapa Island, 12 miles from the southern California mainland, is one of five islands in Channel Islands National Park and is just over 700 acres in size. Segmented into three islets, east Anacapa was treated with aerially applied rodenticide in fall 2001; the same rat eradication measures will be used on middle and west Anacapa in 2002. Courtesy of Tim Hauf; interpretation by National Park Service
Kate Faulkner Gregg Howald Steve Ortega |
 |
 By Kate Faulkner, Gregg Howald, and Steve Ortega Located off the southern California coast and part of Channel Islands National Park, Anacapa Island provides critical habitat for seabirds, pinnipeds such as California sea lions, and endemic plants and animals. The island’s steep, lava rock cliffs incorporate numerous caves and crevices that are particularly important for the increasingly rare seabird species, Xantus’s murrelet and ashy storm-petrel. The largest breeding colony of the California brown pelican in the United States also occurs on Anacapa Island, and a unique subspecies of deer mouse (Peromyscus maniculatus anacapae) occurs only on this island. Unfortunately, the Anacapa ecosystem has been degraded by the nonnative black rat (Rattus rattus) that preys on birds, reptiles, amphibians, and invertebrates. In the mid-1990s, staff of the national park met with biologists of the Island Conservation and Ecology Group to discuss black rats and investigate solutions to the problems they pose. The Island Conservation and Ecology Group was very active internationally in the restoration of island ecosystems through the eradication of nonnative species. They described how rats had been successfully eradicated from various islands, particularly in New Zealand. Thereafter, the former Western Region of the National Park Service funded a research proposal to determine if and how rats could be eradicated from Anacapa and through a cooperative agreement partnered with the conservation group to do the work. But Anacapa Island presented special challenges. Its extensive steep cliffs would complicate placing rodenticide bait into the territory of every rat. The endemic deer mice would feed on any bait that was attractive to the rats. Additionally, the endangered California brown pelican, extremely sensitive to disturbance, breeds and nests on a large portion of Anacapa Island eight months of the year. Following extensive consultation with experts, Channel Islands National Park and Island Conservation and Ecology Group determined that rats could be eliminated through the distribution of bait pellets containing brodifacoum, the anticoagulant used in the majority of successful rat eradications, from a hopper suspended under a helicopter. The bait application would need to happen in the fall, the end of the dry season, when rats are very hungry and numbers of human visitors and birds are relatively low. Protection of the native deer mouse would be achieved through two measures. First, a small population of the mice would be held in captivity, preventing exposure to the bait and allowing for their restoration. Second, only the eastern portion of Anacapa Island would be treated in the first year, ensuring survival of wild deer mice on middle and western Anacapa, which would be treated the following year. Extensive ecological monitoring before and after the rat eradication operation would be needed to determine the environmental impacts of the project. Fortuitously, the American Trader Trustee Council, consisting of the California Department of Fish and Game, National Oceanic and Atmospheric Administration, and the U.S. Fish and Wildlife Service, had court settlement monies resulting from a southern California oil spill in 1990. In part, the purpose of the settlement monies was to restore seabird populations injured by the spill. The trustees supported eradication of the black rat from Anacapa Island because it is one of the most significant islands for breeding seabirds in southern California. They expect to spend approximately $1 million for rat eradication and another $1 million for pre- and post-eradication monitoring, education programs, and efforts to prevent future introductions of rodents to the island. Following public input and application for a permit to aerially apply the bait, the first phase of the operation was completed in December 2001 when east Anacapa Island was treated. Channel Islands National Park and its partners are currently monitoring the site to determine whether all rats were eradicated, and the results look promising so far. The park is also monitoring impacts to non-target species and the recovery of species impacted by rats. Phase II, treatment of middle and west Anacapa, is planned for fall 2002. |
|
This material is from Natural Resource Year in Review--2001, published by the National Park Service, U.S. Department of the Interior, in May 2001 (publication D-2255) /YearInReview/yir/yir2001/05_risks/05_5_faulkner.html Last Updated: |
