Arctic Tundra Animals

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Author: Tricia Edgar

In the winter, there’s a big chill up in the Arctic, and arctic tundra animals need to be tough to stay warm. How do they adapt to the extreme cold?

The body mass index (BMI) is an approximate measure of body fat. In humans, it’s often used to see if someone is in a healthy weight range for their height. However, we can also use it to see how certain other animals have different amounts of fat to help them survive in a challenging Arctic environment.

Problem: How does an animal’s body mass index help it survive in the Arctic tundra?


  • Calculator
  • Clay
  • Old wool sweater
  • Shortening
  • 2 kitchen gloves
  • 4 rice bag hand warmers
  • 4 wearable thermometers
  • Notebook
  • Pencil

Procedure 1: Calculating BMI

  1. To find an animal’s BMI, take the animal’s mass in pounds and divide it by the square of the animal’s height in inches (to square a number, multiply that number by itself).
  2. Once you have the answer, multiply this by 703 to get the BMI.

BMI Formula

  1. Let’s try calculating the BMI of a typical male walrus as an example. This walrus weighs about 2000 lbs and is 120 inches long. First, multiply 120 by 120 to get 14,400. Divide 200 by 14,400 to get .139. Multiply this result by 703 to get 97.717.
  2. Try calculating the body mass index of other Arctic animals!
  • A pika is about 8 inches long and 0.375 lbs.
  • An Arctic ground squirrel is about 15 inches long and 1.6 lbs.
  • Research other Arctic animals and see what their body mass indexes are.

Procedure 2: How do Animals Survive the Arctic Cold?

  1. We’re going to make a different enclosure for each of three hand warmers. The fourth hand warmer will be our control.
  2. Create and dry a natural clay container that the rice bag can slip into easily. The walls of the container should be about ¼ inch thick.
  3. Using an old wool sweater as your fabric, cut out another container that’s just a little bit larger than a rice bag. This should also be about ¼ inch thick.
  4. Finally, fill a rubber kitchen glove with shortening, and place another glove inside it to create a ¼ inch thick, shortening-filled barrier.
  5. Warm up four hand warmers in the microwave according to the included instructions.
  6. Place a wearable thermometer on each one. Wait a minute and read the temperature displayed by each thermometer, noting it in your book.
  7. Put each of three of the rice bags into one of the three containers that you have created, and place them outdoors when it is cold.
  8. After ten minutes, take a peek at the thermometers and record the results. What happened to each rice bag?
  9. Continue taking temperature readings until all of the bags feel cold to the touch.


The rice bags that stay in the clay container “den,” the wool sweater “fur,” and the shortening “fat” will all stay warmer than the bags that are exposed to the elements. Animals that rely on fat (sometimes called blubber) to survive will have a higher body mass index. They use this fat to keep themselves warm.

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