Socorro Island tree lizard Urosaurus auriculatus
Life: Found only on Socorro, across most of the island but missing from land eroded by sheep. Adults average about 66 mm from snout to vent. Endangered (Wikipedia).
The islands
Four volcanic islands
Far offshore, almost uninhabited
The Revillagigedo Islands lie about 386 km southwest of the tip of the Baja California Peninsula. Apart from two small naval bases they are uninhabited (UNESCO). Socorro is by far the largest (Wikipedia).
| Island | Area (km²) | Highest point |
|---|---|---|
| Socorro | 132.06 | Cerro Evermann, 1,130 m |
| Clarión | 19.80 | Monte Gallegos, 335 m |
| San Benedicto | 5.94 | Bárcena, 310 m |
| Roca Partida | 0.014 | 34 m |
The volcanoes are still active. On 1 August 1952 Bárcena erupted on San Benedicto and buried the island in ash and pumice up to 3 m deep; all its plants and land animals were wiped out, and the San Benedicto rock wren went extinct that morning. Seabirds returned the next breeding season (Wikipedia). Socorro last erupted in 1993, under the sea off Punta Tosca (Wikipedia).
At least 33 plant species are found only in these islands (UNESCO); 21 of them only on Socorro (Wikipedia).
Reptiles
Two lizards and two snakes
Every one found nowhere else
The islands have two endemic lizards and two endemic snakes (UNESCO). No photos yet on this page; each card links to photos online.
Clarión Island tree lizard Urosaurus clarionensis
Life: Found only on Clarión Island (Wikipedia).
Clarión Island whipsnake Masticophis anthonyi
Life: Found only on Clarión Island (Wikipedia).
Clarión nightsnake Hypsiglena unaocularus
Life: Reported by William Beebe after a 1936 visit, then struck from the record when later visitors could not find it. A Smithsonian team found eleven 79 years later, and genetic tests showed it is a species of its own. Beebe described it as small and dark brown with lines of black spots (Scientific American).
Restoration
Sheep, cats and pigs
Introduced animals and their removal
Invasive animals are the greatest threat to the islands (UNESCO). Sheep were brought to Socorro in 1869, cats became established after 1953, and pigs reached Clarión in 1979 (Wikipedia). Pigs and sheep have since been removed from several islands and cats on Socorro greatly reduced; unusually for islands this size, rats never arrived (UNESCO). Socorro’s sheep were gone by 2010 (Wikipedia).
Protection
Mexico’s largest fully protected marine reserve
How the islands are protected
The islands became a biosphere reserve in 1994 (Wikipedia) and a UNESCO World Heritage Site in 2016 (UNESCO). In November 2017 Mexico declared the Revillagigedo National Park, 148,087 km² of ocean closed to fishing and other extraction (Pew 2018). Four threatened species of sea turtle are found in the park (Pew 2018), and a large green turtle was seen at Las Cuevas on San Benedicto (trip report 2001).