Sssnakes on Vancouver Island
- Created: Wednesday, 18 May 2016 10:46
Spring is in full swing; the birds are chirping, the gardens are lush and the snakes are out.
Do not fear, the snakes of Vancouver Island are non-venomous and feed primarily on slugs and worms. Both of these photos to the left show a Northwestern Garter Snake (Thamnophis ordinoides) attempting to chow down on a chunky black slug (Arion ater). Snakes have a modified lower jaw that can separate into two halves (they do not dislocate their jaw as commonly thought), thus enabling the snake to eat food that is considerably larger than their own head. The largest part of the snake's body is often what limits the size of prey that can be consumed.
(BOTH: Northwestern Garter Snake, Thamnophis ordinoides eating a black slug, Arion ater. Photo credit LEFT: Micheal McIlvaney & RIGHT: Katie A.H. Bell)
There are two major groups of snakes on the island: the Sharp-tailed Snake (Contia tenuis) and Garter Snakes (Thamnophis spp.). There are three species of Garter Snakes, including the Common Garter Snake, Thamnophis sirtalis, the Northewestern garter snake, T. ordinoides, and the Western Terrestrial or Wandering garter snake, T. elegans). All of these four snake species are active during the day (diurnal) and primarily terrestrial, although all Garter Snakes can swim and T. elegans is often found near/in water feeding on juvenile amphibians and/or very small fish.
All three species of Garter Snake are common throughout BC and not at risk of extinction (yellow-listed). Distinguishing between these three types of Garter Snake is mostly based on morphology; primarily, colour and patterning. All of these snakes have stripes that run the length of the body, however the colour and brightness of these stripes vary. An experienced snaker may also identify the species by counting the number of top lip (labial) scales.
The Western (Terrestrial or Wandering) Garter Snake (snake on the LEFT in the photo) is the most distinguishable, with black spots that invade the prominent yellow/orange mid-dorsal stripe, making it appear zigzagged.
Next, the Common Garter Snake (RIGHT in the photo) is the most familiar as it is the most common and also three distinct yellow stripes and red/orange bars running along either side of the mid-dorsal stripe.
Last but not least is the Northwestern Garter Snake (MIDDLE in the photo). This species varies greatly in appearance, often dull brown and with less prominent/incomplete/absent dorsal and/or lateral stripes. Thisspecies also has albino and melanistic (all black) morphs.
(Three species of Garter Snake found on Vancouver Island, from LEFT to RIGHT: T. elegans, T. ordinoides, and T. sirtalis)
The most secretive and smallest snake species on Vancouver Island is the Sharp-tailed Snake, Contia tenuis. This is red-listed in BC and considered endangered by the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) due to its low population size and secluded range (southeast Vancouver Island, Gulf Islands and Pemberton). This snake is also reliant on Garry Oak meadows, which are native and biologically rich ecosystems that have been devastated by European settlement and continued development.
You can identify this snake species by its small, sharply-tapered and pointed tail. Also, these snakes have fairly consistent body colouration (greyish yellow/red-brown) without any distinct stripes.
HAT has been working to help the Sharp-tailed Snake since 2005, identifying and protecting suitable habitat in the region to conserve it. To learn more about what HAT is doing for the Sharp-tailed Snake check out: http://www.hat.bc.ca/sharp-tailed-snake-stewardship/about-our-program.
(Sharp-tailed Snake, Contia tenuis. Photo credit, Christian Engelstoft)
Remember, all of these snakes are completely harmless. Better yet, as slug-eaters they are great friends for your gardens; slugs munch on the leaves, as well as ripening fruits and vegetables of plants.
By Katie Bell, HAT Volunteer and Wildlife Conservationist