NWT Species at Risk

Red-sided Garter Snakes are the most northern snakes in North America and can be found from northwestern Ontario to eastern British Columbia. The NWT population of Red-sided Garter Snakes is at the northernmost edge of the species’ range.

In the NWT, Red-sided Garter Snakes are found near Fort Smith, inside and outside of Wood Buffalo National Park, where the karst landscape provides the caves and crevices snakes use for hibernation. There are 11 known or suspected overwintering locations within about 25 km of Fort Smith, of which five are in the NWT.  Red-sided Garter Snakes are also seen along the Little Buffalo River and near Hay River and Fort Resolution, which suggests there may be hibernation sites in these areas. 

Range map information

Red-sided Garter Snakes are ectotherms, meaning they primarily rely on their external environment to regulate their body temperature. They adjust their temperature through behaviours such as basking in the sun or taking cover under rocks and logs. In the winter, they hibernate underground below the frost line in rock crevices, animal burrows or other cavities. They often hibernate in large groups that may include hundreds of snakes.

Red-sided Garter Snakes are preyed upon by birds and mammals such as hawks, ravens, weasels and foxes. The snakes themselves are predators that eat wood frogs, chorus frogs and various other small animals. In summer, they are often found around freshwater marshes where there are frogs to eat. These summer habitats may be far from hibernation sites, so the snakes have to move long distances each spring and fall.

Red-sided Garter Snakes mate mostly in the spring. In April and May, at the Salt River Day Use Area in Wood Buffalo National Park, snakes can be seen mating after they leave hibernation. Snakes form “mating balls” as many males attempt to mate with a single female. Sometimes a male will pretend to be a female, causing other males to cluster around them and help warm them up.

Red-sided Garter Snakes do not lay eggs; instead, the female incubates the developing snakes in her abdomen and gives birth to live young. In late summer or early fall, groups of females may give birth together at sites that offer protection from predators (for example, brush or rock piles). Their litter size is usually small, e.g. five to 20 young.

In the North, female Red-sided Garter Snakes reproduce only every second year, or less often. Males take one to two years to reach sexual maturity; females take three years. Their life span typically ranges between six to 12 years, but can reach over 20 years.  

Red-sided Garter Snakes are harmless to humans but may release a musk (smelly liquid) if handled or disturbed. They communicate by picking up scents in the environment with their tongues, using a special organ called the vomeronasal organ. These scents help them choose mates and reproduce.

Little is known about population size or trends for Red-sided Garter Snakes in the NWT. Information from one hibernaculum just south of the NWT border, in Wood Buffalo National Park, suggests a stable population from the early 1980s to about 2011, but up to date estimates are not available.

Red-sided Garter Snakes hibernate in specific, small areas – which means a single threatening event could negatively impact many of the NWT’s snakes at once. This is a key reason why they were assessed as a species at risk in the NWT.  

In recent years, severe wildfire and drought have impacted the habitat of Red-sided Garter Snakes in the NWT, and climate change makes their future more uncertain. Snakes are also killed while crossing NWT roads, especially while emerging and dispersing from their winter dens. Roadkill mortality has been linked to snake population declines in other parts of Canada.

The NWT Wildlife Act prohibits damaging or destroying a snake hibernaculum. Additionally, Wood Buffalo National Park protects a large area of Red-sided Garter Snake habitat – including some key overwintering sites – from impacts of human activities.

In 2024, the NWT Species at Risk Committee assessed Red-sided Garter Snake as a species of Special Concern in the NWT. They determined that threats, combined with the fact that the species occupies only a small area in winter, put it at risk of becoming Threatened or Endangered. Red-sided Garter Snake is currently under consideration for addition to the NWT List of Species at Risk.

Red-sided Garter Snakes can travel long distances, so snakes from secure populations in northern Alberta could likely repopulate areas in the NWT if needed. This reduces the overall risk of snakes disappearing from the NWT.