Moose evolve to withstand the rigors of winter

Willow, a 5-month-old calf, follows her mother, Connie, as they walk through the free-roaming area at Northwest Trek Wildlife Park.
Willow, a 5-month-old calf, follows her mother, Connie, as they walk through the free-roaming area at Northwest Trek Wildlife Park. Courtesy

North American moose, known to scientists as Alces alces americanus, are native to North America. They can be found throughout Alaska, Canada and northern parts of the lower United States. Evolution has shaped this species into powerful animal that has adapted to endure cold weather. In fact, a moose doesn’t just tolerate Northwest winters — it actually thrives here.


When you leave the house in December, you might bundle up in a jacket, hat, gloves, and boots — thick clothing designed to keep heat close to your body.

Moose have a built-in solution: a super-insulated “jacket” made of fur. Long, hollow hairs and a dense, soft undercoat keep moose warm and cozy in temperatures that would make the rest of us shiver.

1,500 That is how much an adult moose can weigh, in pounds. Smaller adult moose might weigh 800 pounds.

Hollow hairs help moose retain heat because they add an extra layer of trapped air, just like a puffy jacket. This type of hair is also found on deer, polar bears, mountain goats and other mammals. Many animals with hollow hairs also have dark skin, which absorbs heat better than light skin.

A moose’s giant snout is something to behold, and it, too, serves a purpose in winter. When humans inhale cold air, it goes directly into our lungs.A moose’s elaborate nasal passage forces air through a long, winding path that heats the air before it reaches the moose’s lungs.


A typical adult moose could weigh anywhere from 800-1,500 pounds. Those massive bodies help moose retain heat. That’s because the ratio of outer body surface exposed to cold air is relatively small compared to the size of a moose’s internal structures (bones, muscles, fat, and organs). In combination with that insulating fur, this body type helps an adult moose keep warm in very cold temperatures.

Male moose, called bulls, also don’t devote any energy toward growing antlers in the winter. Instead, this annual transformation begins in the spring, when energy sources (food and heat) are abundant.


A moose’s diet consists mostly of leaves, twigs, grass and other vegetation, also called browse. Along with other large mammals like musk ox and caribou, moose eat more browse toward the end of the year. This is kind of like stocking up your pantry in the fall so you don’t have to leave the house as much in winter.

Once cold temperatures hit, a moose conserves energy by moving as little as possible. Because nutritious browse is harder to find in winter, the moose draws energy from the fat it has built up in the previous months.


Cold winter nights are the best time to stay indoors, wouldn’t you say? A moose would agree. However, a moose’s shelter doesn’t involve a couch, a blanket and Netflix. Instead, they seek out areas with plenty of browse on the ground and a forest overhead to provide cover.

Believe it or not, one purpose of this shelter is not to keep warm, but to keep cool. Yeah, you read that right: a moose is so well-insulated that it may actually feel too warm in winter temperatures over 23 degrees Fahrenheit. On warmer winter days, a moose might even lie in the snow to cool down.

When moose need to move from one shelter to another in search of browse, they can use their long front legs and powerful shoulder muscles to trek through snow up to 3 feet deep. In warmer months, when they aren’t slowed down by snow, they can run up to 35 mph.

Get up close

Northwest Trek Wildlife Park in Eatonville is home to Willow, a 5-month-old moose calf. The young moose can often be seen with her mother, Connie, as visitors tour the 435-acre free-roaming area from the comfort of a heated tram. Learn more at nwtrek.org.