Herpetofauna de la isla el muerto

Bull. Chicago Herp. Soc. 46(10):129-133, 2011

Notes on the Herpetofauna of the Northwest of Mexico: Herpetofauna of Isla El Muerto, Ensenada, Baja California, Mexico
David Lazcano 1 , Gustavo Arnaud 2, Oscar Cruz 2 and Eli García-Padilla 1 Introduction and Background The islands of the Gulf of California are an important natural laboratory to study ecological and evolutionary models usingherpetofauna as an example (Grismer 1994a,b,c,d,e; Grismer, 1999a), and they have been classified as a priority area for the conservation of biodiversity in Mexico (Vázquez-Domínguez et al., 1998). Island species need extraordinary attention because of their limited distribution, as well as being sensitive to pressure such as the destruction of habitat, the introduction of exotic species (Dodd,1987), and the illegal extraction of species (Mellink, 1995). Given that relatively little is known about the species that are found on the islands (Grismer, 2002), it is important to define the state of conservation of each island and its species. This report describes our investigations of the herpetofauna of Isla El Muerto (also known as Miramar Island), one of many small islands belonging to Mexicoin the Gulf of California. Mexico is a megadiverse country with a high diversity of reptiles (804 species) (Flores-Villela and Canseco-Márquez, 2004). Part of this extraordinary diversity is on islands (Case, 2002; Murphy and Aguirre-Léon, 2002). Islands are fragments of natural habitat that have established, adapted, and evolved species and communities separated from the continent, and may alsocontain continental species along with the island species. Insular biota thus are diverse, unique in the world, and of critical importance for global biodiversity (CONABIO, 2008). Island environments are also sites of reproduction, nesting, resting, and feeding for marine wildlife and migratory birds (Tershy and Croll, 1994). However, because most of the island species have evolved in the absenceof large predators or herbivores, they have no defense or cannot compete effectively with such threats (e.g., man or invasive species), which makes them particularly sensitive and extremely vulnerable (Diamond, 1989; Sánchez-Pacheco et al., 2000). Other megadiverse countries with island territories include: Indonesia with 16,000 islands, Philippines with 9,000 islands, Malaysia 500 islands, andPapua New Guinea with 300 islands (Atlas Geográfico Universal, 2006). There is some disagreement in the literature concerning the number of islands each country has, but the countries have one thing in common: many of the islands are uninhabited by humans, making them excellent areas to study endemic herpetofauna. Within our hemisphere the Caribbean area has produced dozens of excellent articlesabout evolution and species. The islands of Gulf of California More than 100 islands and islets were formed in the Gulf of California during the long process of separation of the Baja California peninsula from the mainland that began about 4 million years ago (Carreño and Helenes, 2002). They form an important refuge for colonies of resident and migratory birds, as well as marine mammals. They arealso an important refuge for many endemic species of several other taxonomic groups, including reptiles (CONANP, 2000). The herpetofauna of the islands in the Gulf of California comprises more than 115 species, of which almost 50% are endemic (Grismer, 1999b). In 1978 the islands of the Gulf of California were declared as a reserve and refuge areas for migratory birds and wildlife, aiming toconserve the natural resources of the islands, with an emphasis on endemic species; on 14 July 2005 the islands were incorporated into the list of the Natural Heritage of humanity by UNESCO (CONANP, 2000). Among the rattlesnakes found on Gulf of California islands, 9 species are listed in the Mexican wildlife agency with “Special Protection” (SEMARNAT, 2010). These are Crotalus atrox, C. catalinensis,...