Rubber Boa. Charina bottae

Description: A small boa, less than 800 mm in total length. Head not set off from neck. Eye small, with vertical pupil. Head scales large and irregular. Chin shields small. Dorsal body scales small, smooth, in 32-53 rows; ventral scales 182-231. Anal plate entire. Subcaudal scales single, 24-43 in number. Tail short and blunt, capped by a rounded plate. Pelvic spurs present in both sexes, but more well-developed in males. Dorsal colour uniform olive green to tan or red brown to dark chocolate brown. Venter yellowish, with or without orange or brown mottling.

Variation: Juveniles pink to tan above, with light yellow to cream venter. There is some sexual dimorphism, with females achieving greater absolute size and maturing at a greater size.

Natural history: This species generally prefers moist coniferous forests and woodlands, but may be found in more open areas where sufficient cover exists. It is found from sea level up to 3,050 m. It is able to climb trees, swim and burrow. The diet consists chiefly of small mammals, which they constrict, but they are also known to take insects, lizards and salamanders. Musk is produced from anal glands.

Reproduction: This species is viviparous. The young are born from September to November. The litter size is two to eight, and young average about 7.5 gm and 220 mm in total length.

Distribution: Known to occur from Quesnel in the interior of B.C. south to the San Bernadino mountains of southern California, and east from the northern California and Oregon coasts to north central Wyoming and south central Montana. The northeastern species range limit appears to be the Continental Divide. Records from the Kootenay River area and Glacier National Park (U.S.) are within fifty kilometres of the Alberta border. If present in Alberta, it is probably restricted to the region between Crowsnest Pass and Waterton.

Remarks: Three subspecies are sometimes recognized. Charina bottae utahensis closely approaches the Alberta border.

Significant references: Cunningham 1966; Hoyer 1974; Nussbaum and Hoyer 1974; Rodgers and Jellison 1942; Stejneger 1890; Stewart 1977.