Santa Cruz Garter Snake 2006

Santa Cruz Garter Snake, San Mateo Skyline, 2006

Gartersnakes have toxins in their saliva which can be deadly to their prey and their bite might produce an unpleasant reaction in humans, but they are not considered dangerous to humans.

  • Size
    • 18 - 40 inches long (46 - 102 cm). Most snakes encountered are generally 18 - 28 inches long (46 - 71 cm). Neonates are 7 - 10 inches ( 18 - 25 cm).
  • Appearance
    • A medium-sized slender snake with a head barely wider than the neck and keeled dorsal scales. Ground color is gray, brown or black. There is a wide yellowish to orange-yellow dorsal stripe, but with the side stripes absent or obscured.There may be small alternating dark spots on the sides. The throat is white or yellow, sometimes bright yellow. The underside is bluish or greenish sometimes with pink or yellow marks.
    • Some average scale counts: Average of 8 upper labial scales, 6 and 7 not enlarged. 11 lower labial scales. Rear pair of chin shields is longer than the front. The internasals are longer than they are wide and pointed in front. Average of 19 or 21 scales at mid-body.
  • The following description is from Boundy, Jeff. Systematics of the Garter Snake Thamnophis atratus at the Southern End of Its Range. Proceedings of the California Academy of Sciences Volume 51, No. 6, p. 330. 1999.
    • "...midbody scale rows 19 (65%) or 17 (35%) ... vertebral stripe yellow to orange yellow and broad, averaging 4.0 (range 2.7 - 6.5) scale rows in the nuchal area ... lateral stripes absent; dorsum olive black, grading to dark olive at the ventrals; dorsal black spots obscure; iris dark brown; top of head dark olive brown to olive black, with a prominent parietal spot; supralabial suture marks narrow when present; demarcation between dorsal head color and dusky olive supralabials indistinct; chin cream, becoming deep yellow on the throat; venter abruptly becoming olive gray in the thoracic area, continuously darkening posteriorly; prominent yellow-orange midventral suffusion; dark markings absent from transverse ventral sutures..."

Key to Identifying California Gartersnake Species

  • Behavior
    • A highly-aquatic snake, able to remain underwater, but also found away from water. Active during the day, and after dark during very hot weather. Can be active most of the year when conditions allow, but primarily found spring through fall.
    • When threatened, this snake will often escape into water, hiding on the bottom. If it is frightened when picked up, it will often strike repeatedly and release feces from the cloaca and expel musk from anal glands.
    • Adults have been found to forage actively, neonates are sit-and-wait foragers, and juveniles practice both forms of foraging.
  • Diet
    • Probably eats mainly amphibians and their larvae, including frogs, tadpoles, and aquatic salamander larvae (newts and giant salamanders, Taricha and Dicamptodon ), but small fish are also eaten. Captives have also taken small rodents.
    • A study of the diet of T. atratus in the Bay Area1 found that native amphibians are a very important part of their diet, with Sierran Treefrogs being the most important amphibian prey, followed by California Toads, California Newts, and California Red-legged Frogs.
  • Reproduction
    • Courtship has been observed during March and April. Young are born live late summer to early fall.
  • Range
    • This subspecies, Thamnophis atratus atratus - Santa Cruz Gartersnake, is endemic to California. According to Boundy, 1999 2 in his revision of T. atratus into three subspecies, Thamnophis atratus atratus occurs in the "Santa Cruz Mountains and the southern San Francisco Peninsula, from the San Andreas rift lakes to the San Lorenzo River watershed and Uvas Canyon." Intergrades with T. a. zaxanthus occur in the southern Santa Cruz Mountains.
    • (Authorities who do not recognize T. a. zaxanthus show the range of this subspecies also occuring in the East Bay south along the coast and inner south coast ranges into Santa Barbara County.)
    • The species Thamnophis atratus - Aquatic Gartersnake, ranges from Santa Barbara County north through the coast ranges into southwest Oregon.
  • Habitat
    • Creeks, streams, small lakes and ponds, in woodland, brush and forest and grassy ecotones. Seems to prefer shallow rocky creeks and streams. When found in muddy ponds there are usually rocky outcrops nearby.

Santa Cruz Garter Snake Range

Rnage - Gray & Red

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