Rubber Boas are small but stout snakes, usually less than 70 cm long. Their most distinctive characteristics are their lack of pattern and the their blunt tails, which resemble their heads. Their colour is variable but ranges from green to chocolate brown. Their eyes are very small and their pupils are elliptical. Males have vestigial hind limbs on either side of their cloaca which can often be seen as small dark spurs.
Copulation occurs during the emergence period, usually in April. Female Rubber Boas give live birth to 2-8 offspring, ranging from 180 to 280 mm long. Birthing occurs in late August through mid September. It appears that adult females are not capable of reproducing every year and may even be limited to reproducing every three to four years (Hoyer and Stewart 2000) or will attempt to reproduce but low temperatures do not allow the embryos to develop (Dorcas and Peterson 1998).
Rubber Boas feed almost exclusively on small mammals. Their favorite prey are nestling rodents, which they consume in the nest and if attacked by the mother rodent, they will present their tail for the defending mother to chew on. Rubber Boas are also fond of shrews.
Rubber Boas are perceived to be secretive as they are almost always concealed or underground. They sometimes bask near the den site but the only other time they are in the open is when they are making long distance movements. In the spring and fall Rubber Boas are active in the day to avoid cool nights but in the summer they are most active at night.
In BC, Rubber Boas emerge from their dens as spring weather exceeds about 15C. However, they often stay concealed during the emergence period, which can last several weeks. Copulation occurs during this emergence period. When daytime temperatures exceed 20C they will disperse to their summer ranges. Rubber Boas will return to their den in the fall. Dens can be occupied by one individual or contain up to 10 or more individuals.
Rubber Boas are most often associated with low elevation mountainsides. Here they can take advantage of warm aspect slopes, especially during the cooler weather in spring and fall. Mountain slopes often have an abundance of rock, which is also important to Rubber Boas for thermoregulating. Rotten logs and stumps are also important attributes in their habitat, as they will worm into the wood and use it for cover. In grassland Rubber Boas will use rodent burrows for cover and to hunt. Dens are most often in bedrock or rubble but they can also use rodent burrows.
In BC, Rubber Boas are found throughout the warmer valleys in the southern third of the province. The northernmost record is from Quesnel. Outside of BC, Rubber Boas are found only in the western United States and avoid the hottest deserts in Arizona and California.
The inoffensive Rubber Boa is typically not persecuted by humans, and for that matter, rarely encountered. Most threats are a result of residential and agricultural development, flooding from hydroelectric projects, rock quarrying, timber harvesting, and road building. Traffic mortality is an ongoing threat that affects Rubber Boa populations throughout much of their range. Some populations are protected within Provincial Parks and conservation holdings of non-government organizations.
The Rubber Boa is the only boa to occur in Canada. It is in the genus Charina which is Greek for graceful. The species name bottae is named after a Spanish explorer who first described the snake in California (Hoyer 2001). There is only one species in the genus and two subspecies are recognized, the southern and the northern form. The latter is the subspecies that occurs in BC.
Rubber Boas are the most inoffensive of all BC snakes. No one has ever been bitten by this snake, anywhere in their range. When handled, they typically wrap their body around a finger or wrist. Despite being a boa constrictor, they are far too small to restrict circulation when they squeeze. It is illegal to keep one as a pet and they are often refuse to feed and ultimately succumb to starvation.
Dorcas, M.E. and C.R. Peterson. 1998. Daily Body temperature Variations in Free-Ranging Rubber Boas. Herpetologica 54 (1): 88-103.
Hoyer, R.F. 2001. Natural history (and other info) of the Rubber Boa. Available online.
Hoyer, R.F. and G.R. Stewart. 2000. Biology of the Rubber Boa (Charina bottae), with emphasis on C. b. umbratica. Part I: Capture, Size, Sexual Dimorphism, and Reproduction. Journal of Herpetology 34 (3): 348-354.
Recommended citation: Author, Date. Page title. In Klinkenberg, Brian. (Editor) 2021. E-Fauna BC:
Electronic Atlas of the Fauna of British Columbia [efauna.bc.ca]. Lab
for Advanced Spatial Analysis, Department of Geography, University of British
Columbia, Vancouver. [Accessed:
2023-12-01 3:09:50 PM]
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