By Ranger Naturalist Charles M. Bogert
BEFORE discussing the herpetology of Grand Canyon, it should be pointed out that all the problems to be confronted are not now apparent, owing to the relatively small amount of collecting that has been done in the region. Collecting here, as in other parts of the arid southwest, is difficult for while species are fairly abundant, individuals are not. Especially is this true in regard to the snakes. To date three amphibians, thirteen lizards, and thirteen snakes are known to occur within the park limits. Two or three other snakes are almost certain to occur here and collecting in some of the more or less inaccessible areas along both the east and west boundaries of the park will probably reveal the presence of more lizards.
My record of the Lyre Snake, Trimorphodon lyrophanes, from Zion National Park, Utah, probably indicates that this species occurs in Grand Canyon. Likewise, some species of Tantilla should occur here. But the secretive nature of these as well as some other small ophidians makes their collection difficult. Collecting at night by automobile headlight, which has proven so fruitful on the open desert, is, of course, impossible at Grand Canyon, except on the rims, which are normally too cold after dark for nocturnal reptiles. Collecting with flashlight on a mule was tried without success.
Men working in the canyon have the best opportunity to collect snakes and so far this has proved to be one of our best sources of material. Particularly are we indebted to Mr. Lloyd Davis at Indian Gardens for his assistance, and it is hoped that other men may become sufficiently interested (or sufficiently overcome their fear) that they will aid us in collecting.
Several species of lizards in the region in and around the park exhibit considerable variation, perhaps not worthy of even sub-specific rank but interesting, nevertheless. For instance, the Collared Lizards, Crotaphytus collaris, in the canyon are colored somewhat like those of California and southwestern Utah, the males usually possessing a dark patch on the throat and darker lateral patches extending from the posterior of the belly on to the rear limbs. The ground-color above is greyish or pinkish brown in live specimens unlike those to the south on the Colorado Plateau which are decidedly greenish in their general coloration.
The Swifts, Sceloporus, undoubtedly are in need of an extensive revision before problems connected with their taxonomy are settled. There occurs along upper Bright Angel Creek a phase of Sceloporus which I first noticed in 1928 and which several observers have commented upon since. Individuals, both young and adult, are without markings, the upper surface possessing a uniform bronze coloration. Study of the Sceloporus group may reveal this to be a distinct species. Field observations would lead one to expect this, for while inhabiting the rocks along with Sceloporus elongatus it is easily distinguishable and there appear to be no "intergrades".
The Horned Lizards, Phrynosoma, which occur within the park limits only on the plateaus so far as known, are apparently the same on both North and South Rims. Following Van Denburgh, I would call those within the park on the wooded plateau Phrynosoma douglassii hernandesi, while specimens from the desert at Tuba City I have called P. d. ornatissimum. Intergradation would be expected to the east of Coconino Basin where the timber ceases and brushy desert begins.
Concerning the snakes, we have fewer problems of a taxonomic nature. The Gopher snakes, long the bane of existence to herpetologists, present perhaps the hardest problem. While the two sub-species, Pituophis catenifer rutilus and Pituophis catenifer stejnegeri (the latter is not recognized by some herpetologists) have for several years been pointed to as an example of diverging development resulting from the canyon barrier, the finding of specimens well down in the canyon tends to detract from the validity of the barrier hypothesis in this case.
With the reptiles, probably our best example of the canyon as a barrier is to be found in the rattlesnakes, Klauber's sub-species, the Grand Canyon Rattlesnake, Crotalus confluentus abyssus, seems to be nicely consistent, the only specimen so far found to occur outside the canyon walls being a specimen collected this past July by Bert Long and David Smith on the west slope of Cedar Mountain near the east boundary of the park. The specimens of abyssus from the east end of the park seem to be less distinctly marked than those from Indian Gardens and Roaring Springs, but they are distinctly different from the yellowish green Prairie Rattlers, Crotalus confluentus confluentus, found a few miles south of the rim. Rattlers are exceedingly rare along the South Rim and any specimens found may aid considerably in establishing the relationship existing between the "pink" and the "yellow" sub-species of Crotalus confluentus. No specimens have been collected at the canyon edge on the North Rim and the only specimen from the Kaibab Plateau apparently is a juvenile from Jacob's Lake. Any specimens from the Kaibab are likely to prove of great value.
The one Black-Tailed Rattlesnake, Crotalus molusaus, collected in the canyon is of interest in extending the range of this species to the north and the Grand Canyon probably marks the northern limit of its range. Only extensive collecting to the north of the Colorado River in the west end of the park would establish this, however. The Black-Tailed Rattlesnake is apparently not rare in Havasu Canyon, according to a Havasupai Indian with whom I talked.
Regarding the problem of life zones, we have few reptiles which may be regarded as good indicators for a single zone. Of the lizards, only the Desert Brown-Shouldered Lizard, Uta stansburiana stejnegeri, seems to be very strictly confined to the Lower Sonoran Zone. The Gecko, Coleonyx variegatus, probably is confined to Lower Sonoran, but too few specimens are available to say definitely. If we follow the zoning outlined in "Ornithology of the Life Zones" by Randolph Jenks*, we find several desert lizards ranging well up into the Upper Sonoran. I have collected Sceloporus magister on the rim at Yavapai Station which Jenks regards (and properly I believe) as the upper limit of the Upper Sonoran Zone. Likewise, I have collected the Chuckwalla near the top of the Redwall limestone well into the Upper Sonoran Zone.
Except for Sceloporus magister the other members of this genus here seem to have Upper Sonoran propensities, but their range extends well into the Transition Zone. In the case of Phrynosoma the preference for the rim would seem to be one of terrain rather than of climate.
To what extent ophidians are affected by life zones in the canyon not much can be said concerning most species until more collecting has been done. The Western Striped Racer, Masticophis t. taeniatus, the Gopher Snakes (considered as a genus), and the Wandering Garter Snake, Thamnophis ordinoides vagrans, are apparently affected but little by varying conditions between the canyon bottom and the rims while the King Snakes, Lompropeltis, the Patch-Nosed Snake, Salvadora g. hexolepis, and the Bi-colored Ground Snake, Sonora Semiannulata, are probably confined to the Lower Sonoran Zone extending upward into the Upper Sonoran to the base of the Redwall limestone.
Concerning the rattlesnakes, it has been perhaps the climatic factor which has brought about the evolution of the distinct Crotalus confluentus abyssus, a snake confined to the canyon and to the Lower and Upper Sonoran Zones. Collecting to date indicates this. If we dare to offer any hypothesis regarding the origin of the Grand Canyon Rattlesnake, the effect of the canyon as a climatical or environmental basis would appear to be one of the best.
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