Getting rid of rats

E: The Environmental Magazine, Sept-Oct, 2003 by C. Josh Donlan, Tosha Comendant

Two shipwrecks, an endangered seabird, animal rights activists, hordes of ship rats and a helicopter--all on a small island 12 miles off Ventura, California. The Channel Islands National Park and Island Conservation recently united in a $1 million project to remove non-native rats from Anacapa Island in an effort to protect critical nesting habitat for seabirds. Rat predation had reduced one of the largest breeding colonies of Xantus murrelets to just a few pairs, earning the seabird a potential spot on the federal Endangered Species List.

Non-native rats are one of the greatest threats to global biodiversity, and nowhere is this impact more devastating than on islands. Historically, conservationists held few tools to curtail this devastation. But in the early 1980s, New Zealanders developed effective techniques for removing non-native species from islands, and they've now been successfully eliminated from more than 100 worldwide. The trick is to get every last rat, and the tool is rodenticide pellets dropped by helicopters.

Rats arrived on Anacapa Island in 1850, when the paddle steamer Winfield Scott crashed into the island. According to the Anacapa Island project director, Gregg Howald, "By removing rats from Anacapa Island, we are not only saving seabirds from extinction but we are restoring an entire ecosystem."

In addition to the endangered murrelets, Anacapa Island is the sole U.S. nesting location for brown pelicans. Eradicating non-native rats alto protects a native mammal, the Anacapa deer mouse. Before showering the island with rodenticide, biologists conducted in-depth genetic studies of the native mouse and housed a captive population for six months during and after the poisoning.

There were some negative impacts. It was impossible to capture all the native mice and many died due to rodenticide consumption. A few dozen landbirds were poisoned. But, many actions were taken to limit non-target impacts. Biologists live-captured dozens of owls, kestrels, hawks and peregrine falcons, which might have fed on poisoned rats, and temporarily held them in captivity.

But animal rights activist Rob Puddicombe claims that the National Park Service is playing God. "To me the idea of species is just an abstract concept," says Puddicombe, a volunteer wildlife rehabilitator. "These animals are here and alive now. Their lives have value." Puddicombe faces charges for illegally coming onto Anacapa Island and spreading rodent chow filled with the antidote to the rodenticide. While his attempt failed, he gained the support of the Fund for Animals, which led a failed legal attempt to stop the project.

Six months have passed since the rodenticide application and the island appears rat-free and alive with native biodiversity. Researchers have found 17 Xantus murrelet nests on the island--the highest number ever recorded. The native mice have been successfully reintroduced and native lizards and salamanders are now enjoying a rat-free environment. "It's a huge step forward for conservation," says Kate Faulkner, chief of resource management for the park. One pleasant surprise is the first-time discovery of the nesting site of another small seabird, the Cassin's Auklet, on the island. Once known as Rat Rock, the area may now need a new name. CONTACT: Channel Island National Park, (805)658-5730, www.nps.gov/chis; Island Conservation, (831)459-1461, www.islandconservation.org.