Midnight Sun


Glacier Rivers

Plant Adaptations

Animal Adaptations




How Do Animals Survive the Cold Weather of the Tundra?

A Grizzly Bear Mother and Her Cubs


Last night, August 09, it snowed up in the Mountains.


As the sun rises above the mountains, the light begins to spread across the tundra and it slowly begins to warm up.  It was very cold last night.  From the look of the ice on our tent, it was below freezing! 

It dawns on us that it is August.  Back at home people are swimming in the lake.  Here, on the 

tundra, we're shivering as we pack our winter hat, long underwear, gloves, and an insulated jackets that we slept in,  into the top of our backpacks.  We'll need those again tonight.

You must be wondering how the animals that live on the tundra can survive the cool summer nights and the frigid winters.

Today, as we hike, we'll keep a sharp eye out for animals and explore how they survive the cold weather.


Long Life Cycle

Down here is a caterpillar many call the Arctic Wooly Bear.  These little caterpillars survive the freezing cold of summer nights and and the deep freeze of the tundra's winter. Caterpillars in most areas grow for one summer and then transform into a butterfly.   Here on the tundra, caterpillars only grow a little during the short, cold summer. It can take them many years, up to 14 years, to transform into a butterfly.  Over the winter, these 



Over the winter, these caterpillars freeze solid and thaw out again to resume life once it is warm enough. 

caterpillars freeze solid and thaw out again to resume life once it is warm enough.  This caterpillar will eventually transform into a Greenland Sulphur butterfly.


The caribou's body has adapted in many ways to survive the long, cold winters of Denali.

Each leg has two crescent shaped hooves.


Toughing it Out

There is a caribou. These amazing creatures have adapted in many ways to survive the long, cold winters of Denali. First, their hair keeps them very warm.  Their long hairs are hollow and provide very good insulation.  Second, each leg has two crescent shaped hooves. These hooves grow longer in the Fall.  This ensures that the exposed pad between their hooves stays above the snow. Therefore, they stay warmer.  Third, their long legs are often submerged in the deep snow.  They have had to adapt their circulation system to prevent their legs from freezing and to keep the cold from spreading up to their bodies.  The arteries and veins in their legs are very close together.  The outward flowing blood (arteries) warms the inward flowing blood (veins).  This allows their body temperature to remain warm while their legs are colder.



A Deep Sleep

Wow, that's a grizzly bear.  Grizzly bears survive the long Denali winters by going into a deep sleep. Throughout the summer,  Denali's grizzly bears gorge themselves on blueberries, roots, and small mammals.  They stuff themselves around the clock to get enough body fat to survive the winter. When winter approaches they go into their dens that they dig into the soil or find a natural cave.  They fall into a deep sleep where their temperature, 



Grizzly bears survive the long, Denali winters by going into a deep sleep.

pulse rates, and breathing rates become very shallow.  The grizzly sleeps so deep that they can actually have their babies while sleeping and do not wake up during the birth.


They go deep down into their burrows to hibernate during the long, cold winter of Denali.



Look over there.  That is an arctic ground squirrel.  They go deep down into their burrows to hibernate during the long, cold winter of Denali.  There burrows are a maze of tunnels and dead ends.  These dead ends actually trap air.  The warmth from the ground heats the air.  This warm, trapped air acts as insulation against the frigid outside temperature. They also line their dens with grass and other arctic plants to insulate their comfy home.  Then, they hibernate. Their metabolism, heart rate, and breathing slow down almost to a stop. If their burrows are not flooded out by water from melting snow, the

arctic ground squirrel will wake up in the spring and survive on food they have stored until it is warm enough to go outdoors.

It is very difficult for animals to survive out here on the tundra.  Just look at all the animals we saw.  They have had to adapt in a variety of ways to withstand the cold.  Check out some more of the animals that live on the tundra to learn about them and how they survive the cold summer nights and frigid winters. 

The Amazing Animals of the Tundra



So, You Want To Learn More About Alaska's Animal Adaptations?

Animal Adaptations

Life in a Deep Freeze

Animal Adaptations


Try This (Hands-On Fun)

The Perfect Arctic Animal

Animal/Human Adaptations for Survival


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