While walking along the boardwalk on July 4, my eyes were drawn to a distinctive black snake, sunning itself in late afternoon sunshine. Curious, because it was black, I took a photo. The Wildlife Rescue Association of B.C. identified it as a melanistic garter. Further email conversations with Will Husby and Alan Whitehead of the Bowen Nature Club identified this beautiful snake as a western terrestrial garter.
Will Husby pointed out that “Melanism in garter snakes is an adaptation to living close to bodies of cold water…. Being black (melanistic) helps the garter snake quickly reheat its chilled body after a swim. They simply bask in direct sunlight, often on a hot rock on shore, till they warm up.”
The western terrestrial’s head is quite prominent in proportion to its neck. Its body is robust and the tail distinctively long. Adults can reach lengths between 18 to 37 inches; females grow larger than males.
One way to differentiate between different species of garters is “…to catch it and count the scales along the upper and lower lip and side of the ribcage between the top of the back and the belly, and observe the shape of certain scales on top of the snout,” noted Alan Whitehead.
The western terrestrial is the second-most common garter snake in Canada, with a lifespan of up to two years. The habitat is open forest and grassy meadow areas close to shorelines, where they also hunt and hide if feeling threatened. They feed on other snakes, mice, frogs, slugs, worms, fish and even small birds. Their venom, though slightly poisonous to prey, is not a threat to humans. They will bite if feeling particularly threatened and if caught, will release a foul-smelling liquid as their first line of defense.
They hibernate in underground dens and mate during spring. Females don’t lay eggs. They bear live offspring in litters of one to 24, between July and September. Based on the size of the snake I saw alongside the boardwalk (close to 30 inches), my guess is that it was a female, soon to give birth.
Further Reading: Western Garter Snake, Dr. Patrick T. Gregory, University of Victoria; Hinterland Who’s Who.