Adult, 600′, Baja California Sur, Mexico
Same individual as above
SAN LUCAN BLUE ROCK LIZARD
Petrosaurus thalassinus – Cope 1863
IDENTIFICATION:
DISTRIBUTION:
This beautiful species is found in the Sierra la Laguna (and its associated ranges) and Sierra la Trinidad of the Cape region of Baja California Sur , as well as on Islas Espiritu Santo and Partida Sur in the Gulf. Elevational distribution from sea level to 2,020 meters in the Sierra la Laguna.
HABITAT:
Petrosaurus thalassinus is most often found in the immediate vicinity of rocky canyons, boulder-strewn hillsides and arroyo bottoms and sea-side cliffs. These lizards appear to be particularly common on rocks near large trees or other vegetation, and rarely seen in areas where vegetation is non-existant.
Canyon Riparian Habitat, 800′, Baja California Sur, Mexico
Boulders in Tropical Thornscrub habitat, 400′, Baja California Sur, Mexico
Same locality as above
Site of my first Petrosaurus thalassinus observation, 1000′, Baja California Sur, Mexico
NATURAL HISTORY:
This large, diurnal lizard is extremely wary and will usually not allow a human to approach closer than several meters. They are omnivorous, consuming flowers, leaves, seeds and many varieties of insects. Grismer (2002) reports witnessing an adult male P. thalassinus “chase down, capture, kill, and eat a subadult male that climbed onto the boulder on which he was basking.” Breeding takes place in the spring; egg laying occurs in late spring and summer, and hatchlings appear in summer and early fall.
TAXONOMY:
This species is closely related to P. repens, found farther north on the Peninsula. In the past, repens was considered a subspecies of thalassinus.
TYPE:
Described as Uta thalassina by E. D. Cope (1863). Holotype: USNM 5302. Type locality: “Cape St. Lucas [Cabo San Lucas]“, Baja California Sur, Mexico.
PERSONAL NOTES:
In June, 2002 Gary Nafis and I found this species at many localities in the Cape of Baja California Sur. We found them to be abundant in Agua Caliente Canyon near Santiago, and in the boulder-strewn ravines along the highway from La Paz to San Juan de los Planes. At both localities, Sceloporus hunsakeri, Aspidoscelis maxima, Phyllodactylus unctus and Urosaurus nigricaudus were also found in abundance. My first experience with this species was extremely memorable: after arriving at our campsite the night prior, I awoke early to a very chilly morning with overcast skies. After a little birdwatching I made my way toward an isolated boulder pile as the sun began to cut through the clouds. I climbed around on the rocks, hoping to see a lizard in a crevice and upon hearing a “scuffling” noise above me, I looked up and just a few feet from my head was an enormous (close to record size I’m sure) male P. thalassinus! I stared motionless and the lizard did the same, until I moved for my camera and the wary beast ran quickly to a crack. I was struck by the fast that although the weather was cold and the sun had not yet emerged from the clouds, this lizard was substantially heated up and quite active. To this day I have not been able to approach another blue rock lizard so closely.
CONSERVATION STATUS:
This species is abundant where it occurs, and is found on several protected islands. It is in no need of special protection.
REFERENCES:
Cope, E. D. 1863. Descriptions of new American Squamata in the Smithsonian Institution, Washington. Proceedings of the Museum of Nature and Science Philadelphia 15:100-106.