The Baja California rat snake (Bogertophis rosaliae) is a nonvenomous colubrid snake native to Baja California, Mexico; California; and some islands in the Sea of Cortés.
It is a large (total length, 85–150 cm = 59 inches), slender colubrid snake with a long head, large eyes, and smooth dorsal scales. Each dorsal scale contains two apical pits (Price 1990a, 1990b). The dorsum is uniform olive or reddish brown without dark markings on a cream-colored background (Ottley and Jacobsen 1983). Yellowish or greenish coloration extends from the lower sides of the body to the venter (Price 1990b). The iris is yellow-green (Ottley and Jacobsen 1983).
The Baja California rat snake ranges from extreme southern Imperial County southward into Baja California to Cabo San Lucas (Price 1990a). Over at least the northern half of its range, it is known from widely disjunctive locations (Ottley and Jacobsen 1983, Price 1990b). Its known elevations range from near sea level to ca. 300 m. In the United States, E. rosaliae is known from only one road-killed specimen CSDSNH 644161 taken 26 May 1984 on Interstate Highway 8, 3.84 km (2 mi) east of Mountain Spring (Imperial County), California. Although Stebbins (1985) and others believe this locality to be genuine (L. Grismer and G. Pregill, pers. comm.), some have questioned the validity of this record (S. Barry, J. Copp, and C. Fagan, pers. comm.).
Elaphe rosaliae is largely confined to mesic and dry desert habitats (rocky - arroyos and washes) in the immediate vicinity of small springs (Ottley and Jacobsen 1983, Stebbins 1985) but individuals have also been observed on hillsides and dry mesas away from water sources (L. Grismer, pers. comm.). The habitat components critical to this snake have not been identified precisely, but it may require some kind of shrub or tree with a moderately dense crown in which to take refuge because it has been taken in native fan palms (Washingtonia spp.), date palms (Phoenix dactylifera ), mesquite, palo blanco (Lysiloma candidum ), palo verde, and creosote bush associations in the past (Price 1990b). The locations of oviposition sites are unknown.
The life history of E. rosaliae is virtually unknown (Price 1990b). The species seems to be nocturnal or crepuscular and may be surface active during daylight hours under suitable conditions (Ottley and Jacobsen 1983). Nothing is known about reproduction or growth except that clutches with an unspecified number of eggs have been laid in captivity (Price 1990b). The few data on diet and behavior are based on captive specimens and are difficult to interpret in the absence of data on this snake under field conditions. If similar to other rat snakes, it climbs easily (Wright and Wright 1957) and adults are probably long-lived (see Bowler 1977). No data on movement, colonization abilities, or the potential predators of this taxon exist.
