Henry S. Fitch

“ Although some of the records published for Thamnophis sirtalis are erroneous, being based on misidentifications of other species, various outlying records, including those in western Kansas, the Panhandle of Texas, and southeastern New Mexico probably represent localized relict populations that have survived from a time when the species was more generally distributed in this region. The population of T. sirtalis in the Río Grande drainage of New Mexico is geographically isolated and remote from other populations of the species. ”

“ There are few, if any, remaining large areas in the United States where herpetologists have not carried on field work. It may be anticipated that certain rare and secretive species will still be found far from any known stations of occurrence, and seeming gaps in the ranges of these species will eventually be filled. But for the common garter snake the negative evidence provided by the lack of records from extensive areas should be taken into account in mapping the range. ”

“ Most large collections of garter snakes contain misidentified specimens. The diagnostic differences in color and pattern are often obscured, especially if the specimens are poorly preserved. Many specimens deviate from the scalation typical of the form they represent, and key out to other species. Isolated records should therefore be accepted with caution. A case in point is Colorado University Museum No. 46, from Buford, Rio Blanco County, Colorado, originally identified by Cockerell (1910:131) as Thamnophis sirtalis parietalis. ”

“ The red of the dorsolateral area frequently invades the lateral stripe, which sometimes is mostly red, and may even invade the ventrals in parietalis, but in fitchi the red marks are usually confined to the dorsolateral area, and do not invade the lateral stripe. ”

“ In having the dorsolateral area consistently black, with the three uppermost series of red crescents reduced or absent, and in having the ventral black spots reduced or absent, these specimens from Colorado, Wyoming, and South Dakota differ from more eastern and more typical parietalis, and tend toward fitchi, even more strongly than some Idaho specimens tend toward parietalis. ”

“ In the Teton Range and in Yellowstone National Park these garter snakes occur in headwater streams up to the Continental Divide. KU 27956 from Two Ocean Lake 3-1/2 miles northeast of Moran, Teton County, Wyoming, agrees in its characters with fitchi, having the red lateral marks small and inconspicuous, discernible only on the anterior half of the body. The dorsolateral area is dark, almost black. The ventrals lack dark markings.
In Utah, populations of sirtalis occur in the drainages of the Bear, Weber and Sevier rivers and other smaller streams of the western half of the state. ”

“ Only a minority have all the dorsolateral marks red, and in some of these specimens the marks higher on the sides are progressively paler red, having a bleached out appearance. Most typically the marks between rows three to six are some shade of red while the smaller marks between rows six to nine are pale—yellowish, greenish, or buffy. In some the pale area of the lateral stripe is in varying degrees suffused with red, which may extend onto the edges of the ventrals and even to the underside of the tail. ”

“ From extreme southern Colorado south across New Mexico to the Mexican border T. sirtalis occurs in continuous or nearly continuous populations in the Río Grande Valley, and has been recorded from many localities. It has been recorded from relatively few localities of tributary streams (Los Pinos, Abiqui, Santa Fe) all near the main valley. There is one record from the Ocate River, a headwaters tributary of the Canadian River, in the Sangre de Cristo Mountains near other localities in the Río Grande drainage. ”

“ Cope (1900:1076) recognized as a distinct subspecies, Eutaenia sirtalis dorsalis, the same population that we recognize herein as T. s. ornata, and Smith (1942:98) considered the name dorsalis to be a synonym of T. s. parietalis. However, it is almost certain that both authors misapplied the name, since the type of Baird's and Girard's (1853:31) Eutainia dorsalis was obtained in Coahuila, Mexico, between Monclova and the Río Grande, far south of the known range limits of T. sirtalis in Texas. The description does not fit T. sirtalis and almost certainly pertains to another species. ”

“ Colorado. A total of 520 live parietalis has been examined from the University of Kansas Natural History Reservation some 130 miles south and a little east of the type locality in Nebraska. These probably differ but little from typical specimens. The range of individual variation in pattern is especially notable. In those from the Reservation, the ground color varies from dull olive-brown to almost jet black. The markings on the dorsolateral area vary in color, in shade and in extent. These marks are chiefly confined to the skin between the scales of rows three to nine. ”

“ Subsequent more detailed studies by later workers with more abundant material led to the recognition of some subspecies that Ruthven thought invalid and led to the resurrection of some names that he had placed in synonomy. Van Denburgh and Slevin (1918:198) recognized infernalis as the subspecies occurring over most of California and southern Oregon, differing from more northern populations in having more numerous ventrals and caudals and a paler ground color. ”

“ T. s. parietalis may be diagnosed, on the basis of these snakes from northeastern Kansas, as follows: Size medium large (length 23.5 to 34.5, or, exceptionally 43.5 inches in adult males; 32.5 to 46.0 inches in adult females) , dorsolateral color olive to black. Approximately every other scale of the third row is bordered above and anteriorly by a crescent-shaped area of scarlet colored skin. Similar crescent-shaped areas border the scales of the fourth and fifth rows and often two adjacent crescents meet at the ends of an intervening scale and fuse forming an H-shaped mark. ”

“ In each local population of this subspecies the characters seem to be remarkably uniform and stable.
Fig. 2. Diagrammatic drawing of pattern in stretched skin of T. s. fitchi; the pale markings on the black dorsolateral area are scarlet (× 2-1/2) .
Fig. 3. Diagrammatic drawing of stretched skin of T. s. parietalis; the scarlet markings extend farther dorsally than in T. s. fitchi and black spots are prominent on the ventrals laterally. Some individuals of parietalis have much paler ground color, resembling ornata except in minor details (× 2-1/2) . ”

“ Top of head olive, supralabials pale gray, edged with black posteriorly; chin milky white, with dark edges posteriorly on fifth, sixth and seventh infralabials; [pg 298] dorsal stripe yellow; including middorsal row of scales and little more than adjacent half of row on either side of it; dorsolateral area olive-brown with row of black spots on its lower half, these spots elliptical, averaging about size of one scale on anterior part of body, smaller posteriorly ”