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Kootenay National Park

Radium Hot Springs' Remarkable Rubber Boa

A Species of Special Concern

Hidden in a rock crevice or under a fallen log somewhere near Radium Hot Springs lives a small snake that looks like a piece of rubber, or a worm, or not much at all. It's a rubber boa, and if you haven't heard of it, that's not surprising. Not many people have.

A coiled up rubber boa shows its blunt, rounded tail.
The amazing "two-headed snake!"
© Dr. Robert St. Clair

This little boa is nothing like the giant man-eaters that haunt horror movies. In fact, its preferred meals are baby shrews, mice and voles, so it's not exactly a threatening species. They've never been known to bite people – but if they are handled roughly, they will leave a smelly musk on you. If you do find a rubber boa, please remember that it doesn't want to be picked up any more than you would.

Don't be fooled by their small size (30-80 cm long) - these snakes are in the same family as the massive boa constrictors and pythons. Rubber boas are classed in an ancient group of snakes that has been found in 50-million-year-old fossils, and was apparently once widespread in North America. Now, however, only two species remain – the rubber boa, and the rosy boa, which is found in California and Mexico. These are also the only two boas found outside the tropics and subtropics.

British Columbia is the northern limit of the rubber boa's range in North America. There is one record of a rubber boa from Quesnel, BC and they also occur in the dry southern interior valleys, including a population at Radium Hot Springs, associated with the natural hot springs. Rubber boas are secretive and hard to find, so not much is known about their populations. Mostly active at night, they spend about 25% of their time above ground, under cover, and the remaining 75% underground. While they have been found on vacant city lots, they usually live in grasslands and forests, or near streams and lakes.

A map of British Columbia showing boa range in the dry valleys of the southern interior.
Range of the Rubber Boa in British Columbia
© Rare Amphibians, Reptiles, and Mammals of British Columbia, S. Cannings et al. 1999

Since they are cold-blooded, winter would be a tough season for the boas, so they go into hibernation in the fall and re-emerge in April. Because they feed at night, rubber boas also have to deal with cool night-time temperatures throughout the summer. However, the disadvantage of feeding at low temperatures is offset by the benefits of avoiding snake predators like birds of prey.

Rubber boas have prehensile tails and can climb trees – but they seldom venture out from underground or under cover.
Rubber boas have prehensile tails and can climb trees – but they seldom venture out from underground or under cover.
© Parks Canada / Larry Halverson

Rubber boas in the wild may live for over 30 years. One (wild-caught) boa kept in captivity lived to over 70! Like many long-lived animals, boas have a low reproductive rate. Females give birth to two to eight young in August or September. Clutches may be as infrequent as every 4 years, and even a productive female will not have a clutch every year. Their low birth rate and long life span make rubber boas vulnerable to human activity. Because of this, they are classified in Canada as a Species of Special Concern, and in BC as “vulnerable” (blue-listed).

The head and tail of the rubber boa look so much alike that it has been dubbed the ‘two-headed snake.' The head-like tail may serve to distract predators – there are reports of boas coiling up and performing fake strikes with their tails. Or, while a boa devours a litter of baby mice, it can fend off the mother mouse with its blunt, club-like tail.

If you do find a rubber boa, please do not disturb it. Report the snake to Parks Canada staff. Any sightings are helpful in determining the range and numbers of boas in the Radium Hot Springs area.

Where do most of our rubber boas hang out?

The area around the hot springs is a favorite spot. Don't worry – although rubber boas can swim, they prefer to burrow, so chances are you will have the pools to yourself (at least as far as snakes go!).

Did you know? . . .

Even though rubber boas are cold-blooded reptiles, they can keep the temperature of their heads a few degrees higher than their body temperature while they are hunting on cool nights.