Students will be able to understand the need for, and identify the characteristics of, a viable wildlife shelter.
Groups of students design a shelter for an imaginary animal and then present their designs to the class.
a list and descriptions of imaginary animals (see below) or diagrams provided by the teacher; drawing paper; pencils; crayons (optional); scissors; glue; markers; and chart paper (optional)
- Sniffaches – cross between a bear and a beaver;
- Ptarmilemm – cross between a ptarmigan and a lemming; and
- Gyrsquirrel – cross between a gyrfalcon and a squirrel.
Just like humans, all animals need food, water, space, and shelter to survive. An animal’s shelter or home protects it from weather and predators, and provides it with a safe place to raise its young, to hibernate, or to store food. Each species builds a shelter that is architecturally designed for its special needs. By looking at an animal’s shelter, one can learn a lot about that creature’s needs and behaviour.
Unlike humans, animals can’t use tools or machines for house construction. Instead, they have built-in tools like sharp teeth, beaks, claws, or feet that can manipulate natural building materials such as grass, twigs, mud, bark, or fur. Animals have developed some amazing solutions to the problems of insulation, heat, drain- age, ventilation, and waterproofing. Some native cultures have learned to survive by observing animal shelters and behaviours. For instance, humans have learned to build igloos or quinzhee shelters in snowy landscapes by observing animals that burrow into snow to keep warm.
The beaver is truly a wild construction engineer that routinely rearranges its environment to create the perfect shelter. The beaver uses vegetation for both food and building materials. Its most important tool is its large, curved front incisors. With this built-in axe or saw, a beaver can chisel through trees up to 1.2 metres in diameter. Like our hands, a beaver’s front paws can hold and manipulate objects.
Once a suitable lake, river, or stream has been chosen, the beaver constructs a dam to slow the water flow and control its depth. As deeper water won’t freeze solid in winter, the beaver can remain active year-round. If the water gets too deep, nature’s little engineer will open the dam to lower the water level. Construction begins when the beaver piles brush, branches, and logs across running water. Green wood is used because it is heavier than dry wood and does not float. The ends of branches are jammed into the muddy bottom so they face upstream. That way, the current keeps the wood in place. Gaps and holes are then filled with more wood, mud, and even rocks.
Upstream from the dam, the beaver builds its lodge on an island of branches piled together, or against an embankment. In both cases, logs and branches are piled to form the base until it rises out of the water approximately 15 cm. A firm platform is constructed with more twigs, bark, and mud. Then, a dome is woven from the branches or stems sticking out from the pile. The top of the lodge is usually thinner and composed of looser branches to increase ventilation. One or two entrances are built under water, enabling the beaver to drag branches inside its lodge for food. The interior of the lodge is divided into a central chamber, a winter food cache, and a bathroom area.
When finished, the lodge is usually two to three metres high, and two to six metres wide. It takes about a month to finish a home, which will be used for many years. It may not seem cosy to us, but a beaver lodge can stay well above freezing, even when it’s very cold outside.
Arctic ground squirrels hibernate in burrows during winter. Because permafrost is common in the north, the squirrels must choose their burrow sites carefully. Permafrost is frozen ground that never thaws. Above it lies a shallow layer of soil 10 cm to 30 cm thick that thaws in summer and freezes in winter. Because of the permafrost, burrows are usually less than a metre below the surface. Arctic ground squirrels live in colonies of several families in an extensive and complicated maze of burrows and tunnels. A family’s tunnel can be up to 18 metres long, and contain as many as 56 entrances within 45 square metres. The dens in which they hibernate are located off the main tunnel, and are lined with soft grasses, lichens, leaves, and fur. It’s a toasty place to sleep winter away.
Another northern burrower is the lemming, a small rodent of the Arctic and Boreal regions. During summer, lemmings dig short, shallow tunnels that connect chambers used for nesting, resting, or toilet areas. Their winter nests are built on the tundra surface under a blanket of snow.
Many bear species use a variety of winter shelters or dens, such as caves, mossy hollows under low-sweeping spruce branches, hollow stumps, or snow caves. The black bear lines its den with spruce boughs, rotten wood, and soft plants. If the grizzly bear can’t find a natural shelter, it will dig a hole under an overhanging rock on an inclined slope. A pregnant polar bear will dig out a snow cave on a hillside or ice ridge in which to give birth. Sometimes a male will use a snow cave as a temporary shelter during extreme weather or the darkest periods of winter.
The gyrfalcon doesn’t build a proper nest. Instead it places a few sticks, grasses, or moss on an inaccessible, narrow cliff edge. Occasionally, it will nest in trees, or lay its eggs in the nest of another species, such as the rough-legged hawk. During winter, gyrfalcons huddle in nooks and crannies in cliffs where there is overhead cover to reflect their body heat. They also lie on top of their naked legs and feet to keep them warm.
The ptarmigan will roost temporarily in the insulation of soft snow banks. It flies directly into the banks so it will leave no tell-tale footprints for hungry predators. A rock ptarmigan will burrow a little cave no bigger than its body in snow as a night roost. When daylight appears, or if it is frightened by a predator, the ptarmigan will explode from the snow in a whirr of wings.
- Begin with a discussion of shelters constructed or used by beavers, lemmings, ground squirrels, bears, ptarmigans, and gyrfalcons.
- Divide students into groups of four to six and give each group an imaginary animal from the list above. Ask them to design a suitable shelter for their creature.
- Have groups move outside and split up. Sitting quietly for five minutes, each group first imagines that it is the designated imaginary animal, then decides on the kind of shelter its creature needs.
- Back in class, have the groups spend some time in discussion, then design shelters for their animal.
- Have each group report its findings and designs to the class.
Have students choose one particular shelter, then construct a chart to compare its advantages and disadvantages.
- Build a female polar bear’s den outside in snow.
- Build models of shelters, such as nests or beaver lodges.
- Compare and contrast shelters of birds and animals.
- Take a field trip to look for animal and bird shelters.
Ask students to:
- List the advantages for wildlife of having a shelter.
- List some of the characteristics that make a good shelter.
- Give an example of a certain type of shelter and why it is just right for the animal that lives there.
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