Reptiles are cold-blooded animals that typically thrive in warm environments. However, some reptile species have adapted to survive frigid conditions in cold climates around the world.
If you’re short on time, here’s a quick answer to your question: Certain lizard, snake, turtle and tortoise species have evolved behaviors and physical traits to handle cold climates across northern latitudes and high elevations.
In this nearly 3000 word guide, we will cover unique cold climate adaptations, specific cold hardy reptile species, their geographic ranges and cold climate habitats. We also detail how they handle seasonal changes and extreme winter environments.
Key Physical Adaptations That Help Reptiles Endure Cold
Hibernation and Brumation Cycles
Many reptiles that live in cold climates undergo hibernation or brumation cycles during the winter months. Hibernation involves entering a deep sleep state where metabolism slows down dramatically. Brumation is a similar process but reptiles will occasionally wake up to drink water before going back into a dormant state.
Both adaptations allow reptiles to conserve energy and survive frigid temperatures when food is scarce.
Body Structure and Size
Reptiles in cold regions tend to be stockier and larger-bodied than their warm climate relatives. A bulky build helps retain heat more efficiently. For example, the common garter snake in Alaska can grow over a foot longer than the same species in warmer habitats.
Some reptiles like the timber rattlesnake also have keeled scales that allow them to maximize their surface area to soak up the sun’s warmth. Their size and structure essentially act as built-in insulation.
Coloration
Many cold-climate reptiles exhibit darker skin pigmentation. Melanin in dark scales absorbs solar radiation more effectively than light colors. That’s why you often see reptiles like the northern water snake sporting nearly black scales rather than the light brown patterns of their southern cousins.
Some lizards like the Aspic viper even turn nearly black before winter to boost warming from the sun’s rays.
Anti-Freeze Compounds
Some reptiles have evolved natural “anti-freeze” in their blood that prevents ice crystals from forming and damaging cells and tissues. One of the most common cryoprotectants is glycerol which lowers the freezing point of bodily fluids.
Wood frogs are masters of this adaptation, surviving 65% of their body water freezing solid. Painted turtles and garter snakes also use glycerol to withstand frigid temperatures.
Behaviors That Allow Reptiles to Thrive in The Cold
Basking and Baking
Many cold-climate reptiles, like the common garter snake, rely on basking to warm their bodies (1). By exposing themselves to available heat sources like sunlight, they can raise their body temperatures high enough to become active and carry out daily functions.
Some reptiles, like the red-sided garter snake, even engage in group basking by piling on top of one another to pool heat together. This allows them to reach optimal body temperatures faster (2). The warmth gained from basking and baking in the sun gives these reptiles the heat they need to thrive despite frigid surroundings.
Nesting Underground and Under Objects
Many cold-climate reptiles shelter in burrows, crevices, rock piles, and underground to escape freezing temperatures. The common garter snake is known to brumate through winter by holing up communally in mammal burrows or ant mounds (3).
The ability to retreat below frost lines protects reptiles from harsh weather and freezing. Nestled underground or beneath fallen logs and rocks, cold-climate reptiles can safely hibernate through winter in a thawed, stable environment.
Grouping Together
Certain cold-climate reptiles rely on group dynamics to survive freezing winters through a strategy known as communal overwintering. By huddling close in large numbers, they can pool their body heat to keep each other warm.
For example, garter snakes are known to overwinter in dens of up to 8,000 snakes (4)! Grouping together in vast numbers generates warmth vital for making it through frigid months. This remarkable cooperative survival mechanism allows reptiles to inhabit areas too cold for most others.
Specific Cold Climate Reptile Species
Common Side-Blotched Lizards
The common side-blotched lizard (Uta stansburiana) is a small lizard found across western North America. They have adapted to survive freezing temperatures by finding shelter underground or in rock crevices. During winter, they become completely inactive and their metabolism slows down dramatically.
Their blood contains glucose that acts as an anti-freeze to keep them from freezing solid.
Side-blotched lizards emerge on sunny winter days to bask in the sun and raise their body temperature. Their dark scales absorb heat more efficiently. By basking, they can raise their body temperature by 35°F in just 30 minutes.
This allows them to become active enough to search for food before returning to their shelter.
Common Garter Snakes
The common garter snake (Thamnophis sirtalis) has the northernmost geographic range of any reptile in North America. They survive cold winters by brumation – similar to hibernation but reptiles can briefly emerge to drink water before returning to their dormant state.
Garter snakes typically brumate underground in mammal burrows or rock crevices. Here they are insulated from subfreezing air temperatures. Their metabolism slows to conserve energy but they can emerge for brief periods if temperatures rise high enough.
Throughout winter, they lose one third of their body mass burning stored energy reserves.
Painted Turtles
Painted turtles survive winter at the bottom of ponds or slow moving streams. As ectotherms, their body temperature matches their environment. Underwater, the temperature stays a few degrees above freezing allowing their vital organs to continue functioning at extremely slow rates.
Ice forms at the water’s surface while mud at the bottom provides ideal shelter. Painted turtles take advantage of warm winter days to climb out and bask to raise their internal temperature. Their dark shell absorbs heat from the sun.
But any turtle caught out during a sudden temperature drop can freeze in hours.
Wood Turtles
The wood turtle (Glyptemys insculpta) inhabits forests from Nova Scotia down to Virginia. They spend winters buried in the mud at the bottom of rivers and streams, or in nearby burrows on land. When ice covers the water, they remain dormant under the frozen layer.
- Their lowered metabolism allows them to survive 3-4 months without food.
- They tolerate subfreezing temperatures but must avoid complete freezing or they would die.
- Hibernating wood turtles have survived short-term temperatures as low as -0.4°F in lab experiments.
| Turtle Species | Minimum Survival Temperature |
|---|---|
| Common snapping turtle | -0.4°F |
| Eastern box turtle | 14°F |
| Wood turtle | -0.4°F |
For more details on cold weather survival adaptations, check out this article from Michigan State University.
Geographic Ranges and Habitats
When we think of reptiles, we often imagine them basking in the sun of tropical or desert environments. However, there are actually quite a few species of reptiles that have adapted to withstand frigid temperatures and make their homes in cold climates.
These cold-climate reptiles have evolved special adaptations that allow them to not only survive, but thrive in environments that freeze over seasonally.
North America
North America is home to a diversity of cold-climate reptiles. Some of the most iconic include the eastern garter snake, found as far north as western Alaska and all of Canada, and the common snapping turtle, with a range stretching from Central America all the way to the Northwest Territories of Canada (Source).
These reptiles withstand freezing winters by hibernating underground or at the bottom of ponds and rivers, emerging when temperatures warm again in spring.
The common side-blotched lizard inhabits the rocky deserts of western North America and is one of the northernmost lizards in the world. Its range extends all along the West Coast, throughout the western interior, and north into southern Canada.
Side-blotched lizards are active for only 5-6 months per year before settling into underground burrows or rock crevices to wait out long, freezing winters (Source).
Europe and Asia
The common European viper, more famously known as the venomous adder, inhabits forested areas and heathlands across most of Europe and well into Russia and Asia. These stocky vipers live farther north than any other reptile species, with confirmed sightings within the Arctic Circle in Norway (Source).
Adders brumate underground during winter, when temperatures can drop below -4°F (-20°C) for months at a time.
Several species of turtles, including the Siberian pond turtle and Chinese pond turtle, inhabit parts of Russia, Mongolia, and northeastern China. These turtles endure bitterly cold winters by hibernating in pond mud, which remains slightly warmer than air temperatures.
In parts of Siberia and Mongolia, air temperatures can plunge below -40°F (-40°C) while the turtles slumber just feet below the frozen surface of their ponds (Source).
| Species | Range | Adaptations |
|---|---|---|
| Eastern garter snake | Western Alaska to Atlantic Canada | Hibernates underground |
| Common snapping turtle | Central America to Northwest Territories, Canada | Hibernates at bottom of ponds and rivers |
| Common European viper (adder) | Europe and Asia, within Arctic Circle in Norway | Brumates underground |
As these examples illustrate, reptiles display remarkable adaptability to not only withstand, but thrive in environments many animals cannot. Through behavioral and physical evolutionary adaptations, diverse groups of reptiles inhabit areas with extreme winters across the Northern Hemisphere.
Conclusion
While reptiles are generally viewed as creatures of hot climates, many unique species have evolved to inhabit cold regions. These cold-blooded animals have developed specialized physical traits and behaviors to survive freezing winters and thrive across northern altitudes and latitudes.
Understanding how these reptiles endure hostile environments gives us insight into the diversity of adaptations life can develop. It also shows us that complex ecosystems can emerge even in the world’s coldest places.
