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Rattlesnakes!

Large-blotched Ensatina Discovered
in the Sierra San Pedro Mártir, Baja California, México

Two museum associates from the Department of Herpetology published an article detailing their discovery of the salamander Large-blotched Ensatina from a mountainous locality four hours drive south of the border. Clark Mahrdt, a Department Associate, and Dr. Lee Grismer, a Research Associate, described their findings in the journal Herpetological Natural History (1998, vol. 6, no. 1, pages 73-76), along with co-author Ron McPeak.

Ensatina escholtzii klauberi, Large-blotched Ensatina, by Jim Melli It had been speculated that Ensatina eschscholtzii klauberi occurred in the Sierra Juárez by Klauber in 1927 based on the reported locality of an observation from 125 km southeast of the city of San Diego. However, due to the lack of a voucher specimen, many subsequent authors dismissed the record as erroneous. Still, others believed this species would be present in the Sierra San Pedro Mártir, a mountain range further to the south. This belief was based on the continuous nature of the habitat south of the nearest known locality in Pine Valley, San Diego County.

In August, 1998, Clark discovered Large-blotched Ensatina in the vicinity of La Tasajera in the Sierra San Pedro Mártir on a southwest facing slope next to a sparsely vegetated meadow. At this time of year, the Mártirs experience daily afternoon thundershowers which provided enough moisture for the summer activity of these salamanders. Over much of the range of Ensatina eschscholtzii, activity is usually confined to the winter months. Like much of the herpetofauna of the Sierras Juárez and San Pedro Mártir, this record is the southernmost locality of E. e. klauberi, disjunct from its more widely ranging distribution to the north.

Dr. Grismer believes this species dispersed from the north and entered Baja California through montane corridors that opened up 1-2 million years ago. They became restricted to extremely high elevations as the surrounding lowlands warmed up and became more arid during the Pleistocene.

Map from Herpetological Natural History, 1998, vol. 6, no. 1, pages 73-76

Clark Mahrdt served as a Curatorial Assistant to the Department from 1969 to 1974 and is currently a biological consultant in San Diego County. Dr. Lee Grismer is the foremost authority of amphibians and reptiles of Baja California and is a Professor of Biology at La Sierra University in Riverside County.