Located 14 miles off the coast of California, Anacapa Island is the easternmost island in the Channel Islands Archipelago. Comprised of three islands strung closely together (East, Middle and West Anacapa), Anacapa Island is part of the Channel Islands National Park. Native species to the island include the Vulnerable Xantus’s murrelet (now renamed Scripps’s Murrelet), the endemic Anacapa deer mouse and the largest breeding colony of brown pelicans in California.
Once an island with no natural predators for nesting birds, invasive non-native black rats were inadvertently introduced to the island from ships visiting the islands in the 1940’s. The invasive rats decimated native seabird populations by eating eggs and chicks. In 2001 and 2002, Island Conservation, the Channel Islands National Park, California Department of Fish and Game, the U.S. Fish and Wildlife and the National Oceanic and Atmospheric Administration removed the invasive rats from Anacapa Island. In the absence of these invasive predators Xantus’s murrelets (now renamed Scripps Murrelet) rebounded almost immediately with nesting success increasing by 91% the year after the rats were removed. The nesting success has remained at around 90%, compared to just 20% when rats were still there.
This was not the only success story. Since the removal of the rats, ashy storm-petrels have been recorded nesting on the island for the first time ever and the Cassin’s auklet, a small seabird which had been unable to nest on Anacapa Island due to the risk of rat predation, has returned. Populations of the island’s only endemic mammal, the Anacapa deer mouse, are also thriving after the removal of the rats which used to compete with the mice as well as predating on them.