Farallon Islands Foundation: Tres Marias & Revillagigedo Islands

Tres Marias Islands and Revillagigedos Islands

Using FIF Chariman Dick Spight's boat and crew, Island Conservation and Ecology Group scientists visited the Marias islands off the west coast of Mexico to survey the native species and assess the need for eradication of nonnative species. Three of the four islands were confirmed to have introduced mammals, including rats, cats, goats and dogs. One island, San Juanito, was found to be free of introduced mammals and also to have the most intact ecosystem. Removing invasive mammals from the Marias Islands would protect a highly diverse reptile fauna and breeding seabirds including: Red-billed Tropicbird, Red-footed Booby, Brown Booby, and Brown Pelican. Eradication has not yet begun on these islands.

Island Conservation and Ecology Group scientists also visited the Revillagigedos Islands 500 miles offshore. The archipelago consists of Socorro, Clarion and San Benedicto islands. On Socorro, the scientists made an assessment of nonnative species which could be threatening endemic seabirds and passerines (such as the Socorro Mockingbird, Socorro Wren, Socrorro Parakeet, Townsend’s Shearwater). On Clarion Island, rabbits and feral pigs and sheep had destroyed much of the native vegetation and degraded areas where seabirds nested. Most at risk was the highly threatened Townsend’s Shearwater. Pigs and sheep were successfully eradicated, but some rabbits remained and the island needs to be revisited.

ICEG scientists also visited San Benedicto Island and surveyed the seabird fauna on the island. Invasive mammals are not present on San Benedicto, but a volcanic eruption in 1952 destroyed most of the island. ICEG and collaborators investigated the status of the Wedge-tailed Shearwaters on the island. Preliminary genetic data suggest this may be an endemic subspecies or even species of shearwater on San Bendicto.

  • Year of grant: 2002
  • Amount: $93,000
  • Grantee: University Of California at Santa Cruz Foundation