B.C. Reptiles & Amphibians

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Credit: Jade Spruyt

Northern Rubber Boa

Charina bottae

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Description

The Northern Rubber Boa is a distinct, small, thick-bodied snake that is almost always less than 70 cm long. They have loose skin with very small, smooth scales that give it a rubbery appearance. Rubber Boas are characterized by their uniform colour, ‘rubbery’-looking skin, and their blunt tails that resemble their heads. In fact, they are also known as the “Two Headed Snake” as it is solid-coloured, making it very difficult to tell the head from the tail unless very close. The head is blunt like the tail and the eyes are very small with elliptical pupils. They are typically dark olive green or brown with pale yellow-orange bellies. Juvenile Rubber Boas are very small and more pink/orange in colour, very closely resembling a large earthworm. Male Rubber Boas have vestigial limbs on either side of the cloaca that appear as small dark spurs.

Listen to the Indigenous words for “snake” here!

Similar Species

There are two other uniformly coloured snakes in British Columbia that could be confused with the Northern Rubber Boa from afar, though from up close the difference is obvious. The Western Yellow-bellied Racer and the Common Sharp-tailed Snake are both solid-colored snakes, although Yellow-bellied Racers are larger than Rubber Boas and both species have long, pointed tails.

Northern Rubber Boa

Western Yellow-bellied Racer

Common Sharp-tailed Snake

Distribution

The Northern Rubber Boa ranges in North America across the Pacific Northwest as far south as northern California and into British Columbia as far north as Quesnel. Within B.C., Rubber Boas are fairly widespread in the southern third of the province, especially in river valleys, with the highest densities occurring along the U.S. border.
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Habitat

In British Columbia, the Northern Rubber Boa hibernates throughout the winter in rocky crevices, root hollows, or old mammal burrows that dip below the frost line. When temperatures are warm enough in the spring, they emerge from overwintering dens but remain concealed for much of this emergence period, which can last several weeks. Once daytime temperatures are warm enough (typically above 20 degrees Celsius), they will disperse into their summer range. Rubber Boas can be found in a variety of habitats including woodlands, grasslands, coniferous forests, dry pine forests, juniper woods, and riparian areas. Although they are able to occupy a variety of habitats, they generally avoid hot, dry areas and prefer more humid and mountainous areas. Within their habitats, cover objects and burrows are important microhabitat features and they spend most of their lives either concealed or underground. During the spring Rubber Boas are active during the day to avoid the cool nights, but in the summer, they are primarily nocturnal to avoid the arid days.

Reproduction

orthern Rubber Boas mate in the spring very shortly after emergence from their overwintering dens. Rubber Boas are ovoviviparous, giving birth to 2-8 live young in late summer or early autumn. Females generally mate every other year but may be limited to every 3 or 4 years in some instances, especially if temperatures are low which do not allow embryos to develop. Rubber Boas reach sexual maturity after 3-5 years, and have a long lifespan of up to 30 years.

Diet

Northern Rubber Boas do not have a big appetite, and eat less frequently than most other snakes. Their favourite foods are mice and shrews, especially newborn individuals. The favourite hunting tactic of the Rubber Boa is to invade the nest of a rodent to consume the nestlings. If attacked by the mother rodent, they will use their tail as a club and decoy to keep the defending mother at bay while it proceeds to constrict and consume the nestlings. Older Rubber Boas can often be distinguished by the heavy scarring on their tails from the bites of mother mice. Although small mammals are the favourite food of Rubber Boas, they are capable swimmers, climbers, and burrowers, opening up many other prey items. They may also eat bird eggs, nestling birds, small lizards, other snakes, salamanders, or bats.

Conservation Status

Global: G5 (2016)

COSEWIC: SC

SARA:1-SC (2005)

Provincial: S4 (2018)

BC List: Yellow

Learn more about conservation status rankings here

Threats

The Northern Rubber Boa has a patchy distribution and a low reproductive rate, which when combined with the potential threats of road mortality, habitat destruction and fragmentation, or illegal collection, could lead to disconnected populations. This could lead to the species becoming more vulnerable to a loss of genetic diversity, potentially leading to major population declines or extirpations.
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Did You Know?

Fact #1

When being attacked by a potential predator, the Northern Rubber Boa curls into a ball hiding its head in the middle of the ball. The hardened tail is then presented as a decoy, thrashing it about as if it were striking at the attacker. If the predator continues, the Rubber Boa will release a stinky musk from the vent in hopes of deterring the attacker.

Fact #2

Northern Rubber Boas are true boa constrictors, and the only species of boa in Canada. They are in the same family as the Reticulated Python and the Anaconda.

Fact #3

Northern Rubber Boas are the least aggressive of all the snakes in British Columbia. In fact, no one has ever been bitten by a Rubber Boa in any part of its range. If handled, they will typically wrap their body around a finger or a wrist and rest peacefully, as they are too small to restrict circulation in a human. However, despite their perceived ‘friendliness’ and undeniable cuteness, it is illegal to keep Rubber Boas as pets as they commonly refuse to feed in captivity and will ultimately starve.

Species Account Author: Marcus Atkins

References

B.C. Conservation Data Centre. 2011. Species Summary: Charina bottae. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2021). 
B.C. Conservation Data Centre. 2018. Conservation Status Report: Charina bottae. B.C. Minist. of Environment. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2021). 
B.C. Conservation Data Centre. 2021. BC Species and Ecosystems Explorer. B.C. Minist. of Environ. Victoria, B.C. Available: https://a100.gov.bc.ca/pub/eswp/ (accessed Jun 15, 2021). 
B.C. Ministry of Environment. 2015. Management plan for the Northern Rubber Boa (Charina bottae) in British Columbia. Prepared for the B.C. Ministry of Environment, Victoria, BC. 24 pp. 
COSEWIC. 2016c. COSEWIC assessment and status report on the Northern Rubber Boa Charina bottae in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. xiii + 38 pp. 
Environment and Climate Change Canada. 2017g. Management Plan for the Northern Rubber Boa (Charina bottae) in Canada. Species at Risk Act Management Plan Series. Environment and Climate Change Canada, Ottawa. 2 parts, 3 pp. + 24 pp. 
https://www.bcreptiles.ca/snakes/rubberboa.htm 
http://www.canadianherpetology.ca/species/species_page.html?cname=Northern%20Rubber%20Boa 
http://linnet.geog.ubc.ca/efauna/Atlas/Atlas.aspx?sciname=Charina%20bottae