Below Zero Activities

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Winter Wonders

Age: Grades 7-12
Subjects: Biology, Environmental Studies, Social Studies, Mathematics Skills: identification, movement, cooperation, analysis, calculation
Duration: minimum 30 minutes
Group Size: any
Setting: outdoors and indoors
Conceptual Framework References: 2a, 2c, 3d, 4a, 4b, 4c
Key Vocabulary: foot load, surface area, grams, kilograms, centimetres squared

Objectives

Students will be able to:

1. Identify two or more animals that travel easily in snow;
   
   
2. Hypothesize why these animals are good snow travellers;
   
   
3. Experience an efficient way to move over deep snow, and
   
   
4. Calculate food loads of different animals.

Method

Students take the part of either humans wearing winter boots, or lynx wearing snowshoes, and then attempt to collect food tokens. Students also calculate their foot load and compare it to that of the lynx.

Background Animals like the lynx, have adapted to deep snow by developing large feet. The lynx's big paws are like snowshoes. They distribute its weight broadly so that it can pad swiftly and easily over the snow. A deer, however, sinks and struggles in just several inches of snow on its narrow, sharp hooves. Tough snow travelling forces the deer to waste precious energy. Consequently, they have learned to gather in smaller areas or 'yards' over winter months, where they pack down a network of trails for easier travel.

An animal's ability to move on top of the snow is related to the surface area of its foot and also how much weight that foot places on the snow. To estimate the weight or foot load of a four-legged animal, we assume that each foot supports one-fourth of its weight (though the front feet generally carry about 70 per cent). Therefore, foot load is one-fourth of the animal's weight divided by the surface area of one of the animal's feet. The final figure estimates the force that each foot places on the snow.

Foot load generally increases with body size. However, many animals, like the lynx, have a low foot load relative to their body size. Interestingly enough, the lynx's favourite meal, the snowshoe hare, has an even lower foot load. In the evolutionary race to adapt to snowy habitats, the snowshoe hare is still out in front!

We place more weight on our feet than animals do because our weight is distributed over only two feet and not four. That's why people in snowy climates invented snowshoes and skis. These increase our surface area while decreasing our foot load, so that we can get around more easily on snow.

Materials

snowshoes for half the class; graph paper for each student; pencils; weigh scale (in kilograms) or ask students to weigh themselves in kilograms at home; food tokens, such as coloured disks (three or four per student); field of undisturbed snow; calculators (optional); and pictures of animals in winter conditions (optional).

Procedure

1. Discuss and make a list of adaptations that help animals survive winter.
   
   
2. Discuss the importance of a low foot load to winter survival. Have students weigh in if they haven't already done so at home, then convert their weight to grams. Now students are ready to figure out their own foot load.
   
   
   1. First they trace one bare foot on a piece of graph paper marked in square centimetres. Next, students count the number of squares inside their foot outline, including squares that are more than half inside the outline. (Do not count squares that are less than half inside the outline.)
      
   2. Now multiply the number of squares by two to get the total area supporting a student while he or she is standing on both feet.
      
   3. Have each student then calculate their weight load by dividing their weight (in grams) by the area of support (cm2). The calculation is as follows: weight of student (g) (g/cm2) = weight load area of support (cm2)
      

    

3. Compare student foot loads to that of the lynx (32 g/cm2). Which one will be the most efficient snow traveller?
   
   
4. Outside, spread the tokens throughout a designated play area, ideally an open field of deep, undisturbed snow. Twenty centimetres of snow makes a good game, however, deeper is even better!
   
   
5. Divide the group into two teams -- snowshoe hares and deer. The hare put on snowshoes, while the deer wear winter boots.
   
   
6. The two teams line up on an edge of the playing field. The teacher signals the start. Each team moves quickly through the field, collecting as many food tokens as they can within a maximum time limit of five minutes. Note: hares should be more efficient than deer, however, poor snowshoe skills may skew the results!
   
   
7. In class, each team counts their food tokens and compares success rates. Discuss how their experience in the game relates to winter wildlife survival. How can humans decrease their foot load, and so travel more efficiently? What other animals have high foot loads? How do they cope with deep snow?

Variation

Students calculate foot loads of different mammals, such as moose, caribou, shrews, etc.

Extensions

1. Students make a presentation of their findings by developing a large graph showing the relationship of their foot loads to those of efficient animal travellers. Students illustrate the graph to make it an educational bulletin board.
   
   
2. Students examine other physical adaptations of wildlife to winter on both land and water.

Evaluation

1. Explain the benefits of low foot loads for snow travel.
   
   
2. Explain some adaptations made by animals and people with higher foot loads for easier travel on snow.

Copyright 1998 by the Canadian Wildlife Federation.
All rights reserved.