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.
How does an animal’s body mass index help it survive in the Arctic tundra?
- Old wool sweater
- 2 kitchen gloves
- 4 rice bag hand warmers
- 4 wearable thermometers
Procedure 1: Calculating BMI
- 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).
- Once you have the answer, multiply this by 703 to get the BMI.
- 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.
- 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?
- We’re going to make a different enclosure for each of three hand warmers. The fourth hand warmer will be our control.
- 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.
- 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.
- Finally, fill a rubber kitchen glove with shortening, and place another glove inside it to create a ¼ inch thick, shortening-filled barrier.
- Warm up four hand warmers in the microwave according to the included instructions.
- Place a wearable thermometer on each one. Wait a minute and read the temperature displayed by each thermometer, noting it in your book.
- 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.
- After ten minutes, take a peek at the thermometers and record the results. What happened to each rice bag?
- 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.
What would you wear if you went to the Arctic? Since the cold winter weather there can dip to -40 degrees Fahrenheit, you’d be wise to wear warm layers that block the wind.
Growing fur is a good survival strategy for animals in the Arctic: it’s a lightweight way to stay warm. Like a sweater, fur keeps air next to the body, and these air pockets help the animal retain heat. Fur can be challenging in wet conditions, however—it gets heavy, and water reduces the amount of air pockets, making it less useful as insulation. Animals like sea otters need to groom themselves almost constantly to keep air pockets in their fur, which keep the otter warm even though it is wet. Animals that have fur may have a lower body mass index than animals that rely primarily on fat to keep warm.
Fat, which is on the inside the animal’s body, is an excellent insulator because it allows the animal to stay warm even when the animal is wet. It’s also a way for the animal to save energy: during hard times, when there isn’t much to eat, animals can live off their fat reserves. This fat is often called blubber, and the bodies of some Arctic marine mammals can consist of up to 50 percent blubber! This special fat contains a lot of blood vessels. In cold conditions, the blood vessels contract, so that the animal spends less energy heating its body.
When you created a clay house, you built a model den. Dens are a great way for animals to stay warm in the wintertime. Just as you might head into your warm house and burrow under the covers, animals burrow into the ground to keep warm. Animals like pikas live in underground dens in the wintertime, munching the roots of plants and eating their stored food.
Other animals hibernate, slowing down their body functions and spending most of their time resting or sleeping to conserve energy. This way, they can use a lot less energy to survive, and don’t have to eat nearly as much. Marmots and ground squirrels are two Arctic hibernators.
Other animals migrate to stay warm. If your grandma goes to Florida in the winter, she’s not a silly goose – she’s following in the footsteps of many animals that fly, walk or swim to warmer climates to keep warm in the winter. These animals start moving south in the late summer and early fall, and by the time the winter hits with its cold weather and limited food, these animals will have arrived in warmer a warmer place with a better menu. Arctic caribou are known for their long walking migrations, and many birds such as geese fly long distances to warm places. Even butterflies migrate!
Think about the ways that you stay warm in the winter. How are these similar to or different from the ways in which other animals stay warm?