Thursday, 18 July 2013

The Common Garter Snake - An Interesting and Beautiful Reptile

The common garter snake, or Thamnophis sirtalis, is an interesting and often beautiful reptile found in many parts of North America. I used to see this snake frequently, but now that my neighborhood is more built-up the animal is harder to find. An exception was my recent discovery of a snake beside a nearby pond. Unfortunately, it was dead, but at least I was able to get lots of photos.

A Common Garter Snake
Photo by Linda Crampton

There are a number of subspecies of garter snake. The snake's appearance is very variable. Even garter snakes in the same subspecies can look different from each other! The snakes that I've seen in my area  - southwestern British Columbia - have yellow stripes on a dark green, dark grey or black background. Some animals also have blue stripes and/or red patches, producing a very attractive appearance.

Winter Dormancy

Garter snakes have some interesting habits. (Keep in mind that I'm talking about the garter snakes in my part of the world.) They stop eating before they enter their winter dormancy, allowing their stomachs to empty. Garter snakes spend the winter in a den called a hibernaculum. They're often accompanied by other garter snakes and even by other types of snakes. The snakes may form a dense ball of dormant animals. Technically, the dormant state of reptiles in unfavorable conditions is known as brumation instead of hibernation.


The snakes emerge from their hibernaculum in spring. Generally the males appear first, followed by the females. Mating takes place very soon after the snakes emerge from the den. Often many males cover a single female, all trying to pair with her.

Garter snakes give birth to live young in July or August. They are ovoviviparous animals. Their young develop in eggs, but these are retained inside the mother's body instead of being laid. The eggs contain yolk to nourish the youngsters. They hatch inside the mother and the offspring are then born live.  Generally, about 10 to 15 young are born, but some garter snakes have been known to produce as many as 70 youngsters in a litter.

Another view of a common garter snake
Photo by Linda Crampton
Hunting For Prey

The common garter snake is diurnal (active during the day), but it's most active in the morning and late afternoon or early evening. It's carnivorous and a hunter. It feeds on frogs, toads, salamanders, slugs, earthworms and insects. It also occasionally preys on small mammals, birds, fish and other reptiles. The snake enters water at times and can swim, which it does very well.

The tongue is red with a forked, black tip. It's extended frequently to pick up molecules in the air. The tongue is then inserted into the Jacobson's organ in the roof of the mouth, which detects the chemicals on the tongue. In this way the snake can find potential prey. The Jacobson's organ is also used to detect chemicals called pheromones that are released by females to attract males during mating.

Dangers to Humans

Garter snakes shouldn't be handled unless absolutely necessary. The snake often releases a smelly mixture of musk and feces from the vent at the end of its tail when it's handled. It will also bite if it has no other choice.

Garter snakes have long been considered to have a non-poisonous bite, but researchers have now discovered that their saliva is slightly toxic. The toxin may help to subdue the snake's prey. It's harmless to humans. however. Like any animal bite, a wound created by a garter snake bite should be properly cleaned, treated and covered. It will most likely be painful and itchy.

The subspecies of the common garter snake that I see most often is the Puget Sound garter snake (Thamnophis sirtalis pickeringii). It's a very interesting animal. I hope my next encounter is with a live snake instead of a dead one.

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