Red-sided Garter Snake. Thamnophis sirtalis

Description: A medium-sized, slender, elongate snake, attaining a total length of between 460 and 1,300 mm. There are usually seven upper labial scales and ten lower labials, and two pairs of chinshields, with the rear pair being longer than the anterior pair. The dorsal scales are keeled, there are usually nineteen scale rows at mid-body and the anal scale is single. The tail is moderately long. The background colour is dark olive to black. There are dark spots on the back and usually red or orange bars on the sides. The dorsum of the head is primarily olive in colour. The vertebral and lateral stripes are variable and maybe yellow, greenish, orange or blue. The lateral stripe occurs on the second and third scale rows. The venter is bluish and is often darker posteriorly. The throat is whitish.

Variation: Males have knobbed keels on the scales above the vent. Females may be considerably larger than males. Males have relatively longer tails.

Natural history: This species has very broad habitat preferences and tolerances. It often lives in the vicinity of ponds, marshes, ditches, dugouts and streams. It may be found in forested habitat, farms or in urban situations. If molested, it may flee to water or, if captured, bite and / or smear the attacker with foul-smelling anal gland secretion and faeces. It eats fish, amphibians, reptiles, birds, small mammals, worms, molluscs and some arthropods. It is very coldtolerant. Red-sided garter snakes are mildly venomous and may immobilize their prey with oral secretions. These secretions have no effect on man. In Alberta, this species emerges from hibernation as early as mid-April. The distance between hibernation sites and feeding grounds may be as much as nine kilometres.

Reproduction: This species is live-bearing and normally gives birth to twelve to eighteen young, although litters may range from as few as three to as many as eighty-five. The young may be born any time from May to October and average 200 mm in total length at birth. Litter sizes are smaller and individual neonates larger in western Canada than in the east. Mating usually occurs in spring, following emergence from hibernacula, but it may also occur in the fall. Males may mate with many different females and individual females may be inseminated by several males. Gravid females exhibit low rates of movement during gestation and prefer to occupy retreats that provide protection and more suitable thermoregulatory conditions. In the northern parts of its range, there is massive communal denning. Pheromonal cues may play a role in locating the dens.

Distribution: This species occurs at scattered localities throughout Alberta. Its status in the extreme northwest of the province and along most of the Saskatchewan border is uncertain. Although it may occur in all habitat types, it is chiefly a resident of the boreal forest and aspen parkland. It occurs at elevations up to 2,000 metres. Extralimitally, it occurs from south central Northwest Territories and James Bay, south to Florida and the Gulf coast in the east, and southern California in the west. It is absent from most of the arid south western United States, although it is present in parts of New Mexico and Chihuahua, Mexico.

Conservation status: The most widespread reptile in the province, the red-sided garter snake appears at no imminent risk of decline.

Remarks: Twelve subspecies are recognized. Thamnophis sirtalis parietalis is the Alberta subspecies, and this subspecies occurs from the Northwest Territories and east central B.C. south to the Texas Gulf coast, and east from the Rockies to approximately the Mississippi.

Significant references: Aleksiuk 1970,1971a, b, 1976a, b; Aleksiuk and Gregory 1974; Aleksiuk and Stewart 1971; Arnold 1978; Benton 1980; Blanchard 1943; Blanchard and Blanchard 1941,1942; Bona-Gallo and Licht 1983; Burghardt 1975,1983; Carpenter 1952a, b, 1953; Charland 1995; Charland and Gregory 1995; Clark and Chandler, 1992; Clark and Bradford 1969; Cooper et al. 1989; Costanzo 1985,1986,1988,1989a, b, c; Costanzo and Claussen 1988; Crews 1976; Crews and Garstka 1982; Crews et al. 1984, 1986; Dalrymple and Reichenback 1981; Fitch 1940, 1965, 1980; Fitch and Maslin 1961; Garland 1988; Garstka et al. 1982, 1985; Gibson and Falls 1975, 1979; Gibson et al. 1989; Gregory 1974,1977b; Gregory and Larsen 1993; Gregory and Nelson 1991;

Gregory and Stewart 1975; Halpert et al. 1982; Hart 1975; Hawley and Aleksiuk 1975; Herzog and Bailey 1987; Herzog and Burghardt 1986; Hoskins and Aleksiuk 1973; Huey et al. 1989; Jansen and Foehring 1983; Joy and Crews 1985, 1986, 1988; Krohmer and Crews 1989; Larsen, K.W. 1987; Larsen and Gregory 1988,1989; Larsen et al. 1993; Lawson 1989; Macartney et al. 1989; Mutschmann 1995; Peterson 1987; Pough 1977; Rodgers and Jellison 1942; Rosen 1991; Rossman et al. 1996; Ruthven 1908, Schwartz et al. 1989; Secoy and Ramaekers 1980; Seibert 1950; Shine and Crews 1988; Stewart 1965; Sweeney 1992; Tanner 1988; Van Denburgh and Slevin 1918; Whittier and Crews 1985, 1986; Whittier et al. 1985, 1987a, b; Wilde 1938; Young 1988,1989.