Restoration Makes an Instant Impact on Anacapa Island

As Earth Day approaches, Island Conservation will share stories of hope and success in conservation.

The first project of its kind in the United States, the restoration of Anacapa Island, helps the Scripps’s Murrelets avoid “Endangered” listing.

Only 14 miles off the coast of Ventura, California, lies the three islands that form Anacapa Island. They, in turn, are easternmost islands in the Channel Islands National Park, established in 1978.

The Challenge

Thousands of birds use Anacapa Island as a nesting area because of its natural lack of predators. However, invasive black rats brought to Anacapa in the 1940’s on ships traveling to the islands were causing havoc on the islands—biologists discovered high rates of predation on murrelet eggs and found bird bands outside rat nests, evidence that rats were eating young birds. Researchers found that more than 96% of Scripps’s Murrelet nests on Anacapa were being predated by invasive rats.

The Solution

In 2001 and 2002, Island Conservation and its partners removed the rats from Anacapa Island, with subsequent monitoring confirming the rats were completely removed.

Outcome

The removal of the rats had an almost instantaneous effect.

In the absence of the invasive predators, Scripps’s Murrelets rebounded almost immediately, with continued strong evidence of Murrelet population growth through the expansion of breeding area, increased nest occupancy, and a higher number of eggs laid at one time.

Today, hatching success among the Murrelets is greater than 90%, compared to less than 20% when rats occupied the island. Cassin’s Auklets have also re-colonized the island. In 2011, Endangered Ashy Storm-petrels established nesting sites on the island for the first time ever.

With the island free of invasive rats, the island continues to return to what it once might have been.

Featured photo: A 90% increase in hatchling survival of the Scripps’ Murrelet helps avoid Endangered listing. Credit: Shayne Wolf