Bucky Beaver Lives Here
Despite the fine quality of their fur coats, they look a little dumpy. Their teeth also are a little too prominent to be pleasing – but their whiskers are cute. Certainly they are prominent Canadians. On formal occasions they go by the name Castor canadensis, but to their friends they are simply beavers. The plan of action for any beaver couple is to raise their young and to enjoy long healthy lives. This is not a surprising nor an unusual agenda. Nevertheless of all the wildlife creatures that make their home in most parts of North America, the beaver is fast becoming extremely unpopular. The fact is that beavers are the only animals in the world which can change the landscape to suit their own needs and desires. The trouble is that the beavers’ alterations often do not fit the plans of people living in the same area. Then again in other parts of the country, wildlife officials regard beavers as economical wetlands managers.
Back in Alberta, it was in the spring of 1996 that a provincial wildlife official claimed that beavers are the number one nuisance. Because of a successful life style, both cities and countryside support generous numbers of this animal. They cut down trees, plug culverts and flood roads. They dam streams and flood fields and woods. The results are very scenic and excellent for beavers and other wildlife, but extremely expensive for people who often insist on reclaiming the fields and the roads and in planting new trees. As we struggle to protect certain parts of the landscape from the best efforts of the beavers, it is easy to forget how unique beaver talents are and how wonderfully these animals have been designed.
Beavers are engineers and builders. With only their teeth and front paws, they change landscapes so that a safe home can be built and enough food harvested and stored. The lodges or homes are large and conspicuous. Most are about 5 m in diameter and about 2 m high. Animals as large and tasty as beavers, would surely be a popular meal for predators if all the hunter had to do was wait by the lodge until the beaver came home. Obviously, hidden entrances are essential to beaver survival. What the beavers do is to locate their lodge in the centre of a body of water. Then the entrances are hidden under the water, well shielded from the view of predators like wolves. Since the beavers maintain an active lifestyle throughout the year, they must be able to come and go from their lodge even when arctic gales howl. Since most small bodies of water freeze under these conditions, the beavers need to find ponds and streams deep enough so that some liquid water remains below the ice. Since such deep locations are hard to find, the beavers instead undertake to change whatever pond or stream they have selected, into the deep conditions that they need. This is where the amazing dam building skills of the beaver are called into play.
First of all the beaver must select the spot where they will build their dam. It is the sound of trickling water which stimulates the beaver to plug the flow. The point that the beavers typically choose is where the noise of moving water is the greatest. This is roughly the point where the water is moving the fastest. The distance to be blocked is probably the least at this location. Beavers are not committed to any one style of dam. They build whatever it takes to block the flow of water. Dams may be long or short, high or low. Dams as high as 5.5 m have been found. One was documented that was 500 m (one half km) long and 4 m tall. Most are much shorter. When the water flow is sluggish, a dam will be built straight across the streambed. When the current is strong however, the dam is built with a convex curve in the upstream direction so that it best resists the pressure of the water. The beavers instinctively know how to compensate for stress and strains of the water pushing against the dam. On the upstream side of the structure, the dam wall is vertical – but on the other side, it slopes downstream at a 45 degree angle. Such a beaver dam is an extremely stable structure that can resist great water pressure and erosion. These animals even build outlet sluices for disposal of overflow water. The construction, after all, must not be the means of flooding out the lodge during times of higher than normal rainfall. The beavers always make the right engineering choices.
Since the beaver are unique in their water management capabilities, it is obvious that they have been endowed with remarkable characteristics. These animals do not learn their building skills from their elders. They just know them. In Europe, for example, beaver which were hounded almost to extinction and which for generations had no opportunities to utilize their talents, once again are displaying their full architectural expertise.
Besides brain power, each beaver needs the physical ability to actually build dams. These large animals weigh between 16 – 32 kg as adults. In shape they are rotund, with almost no neck and short, stubby legs. On land a beaver’s progress looks awkward and slow, but in the water the same animal swims easily. This is facilitated by hind feet which are fully webbed for swimming. One thing these animals need to be able to do, is spend considerable time under water establishing the footings of their dam. The beavers’ small beady eyes are able to see as well under water as in the air, thanks to a transparent membrane that protects the eyes while submerged. Special valves in the nostrils and ears keep out unwanted water during dives. The oxygen holding capacity of the beavers’ red blood cells must be special too as these animals are easily able to stay under water as long as 15 minutes. So don’t hold your breath waiting for a diving beaver to re-appear!
The beavers’ front paws are small and delicate, without webs. They function almost like hands. They are able to carry objects such as sticks, stones or mud and they manipulate these into place in the course of their building activities. The beaver begins his dam by laying sticks and rocks in the streambed at the desired location. Some sticks are actually pushed into the mud. Stones and more sticks are placed in front of and between the initial markers. A considerable amount of timber is required for the dam. Here too the beaver is appropriately equipped for his task. His front teeth are hardened with a dark orange enamel (not pretty, but effective). The teeth grow continuously and the outer tips grind against each other. This keeps the cutting edges chisel-sharp. With these cutting instruments, beaver can easily fell trees 30 cm or even twice that in diameter. The trees are used in building operations, and as sources of twigs, bark and leaves for food. Another interesting feature of beaver mouths is the fact that their lips can be closed behind their front teeth. Thus while submerged, they can chew without choking on sawdust or water. This gives a whole new meaning to the expression “My lips are sealed” !!
A final design feature of the beaver is their large flat tails. Not only do these serve as a rudder while swimming, but beavers in the water also use them as a warning device. When a beaver slaps the water with its tail, a noise like a pistol shot warns other beaver and might even scare a predator. But the uses of the beaver tails don’t end there. On land the tail props an animal upright when standing or sitting, and it provides support to an animal which is walking on its hind legs carrying building materials or food.
All these remarkable design features make possible the maintenance of a year-round cosy beaver home. Each male beaver selects only one mate and keeps her for life. A couple produce one litter per year. Youngsters stay in the family home until they are two years old. Their life span in the wild is ten to twelve years but in captivity some might last until their twenties or thirties. All winter long the beavers eat sticks from a large collection stored underwater close to the lodge. They particularly enjoy trembling aspen, poplar, willow and birch. One fifteen month study of an adult beaver couple in a national park in Canada, found that these animals cut down 266 trees for their building and eating activities. If such an energetic beaver family were to live in an urban setting, or even in a farm setting – it is easy to imagine that the beavers’ activities would be noticed and would be very unpopular.
Then again in some parts of Canada, beaver ponds represent one of the most important wildlife habitats. These ponds are especially important for ducks which are nesting or raising young. Rather than undertaking expensive management of wetlands, some wildlife jurisdictions simply encourage the beavers to do what comes naturally. Interestingly, some of the new forest cutting practices actually discourage the beaver and thus depress duck populations as well. When buffer strips of mature trees are left beside streams, the area is unattractive to beaver. Anything that discourages the growth of trembling aspen will contribute to lower beaver populations and reduced wildlife variety. Trembling aspen grows best in open territory. Old fashioned clear cutting perhaps had some positive features.
So people pursue their agendas and the beaver follow theirs. When a conflict arises, people try to discourage the beaver. As an article in the Edmonton Journal (May 9, 1996) reported: “People have tried everything to get rid of beavers. They’ve blown up a dam and then put in electric wires so the beavers won’t come back. They’ve tried flashing lights and sirens – the beavers always come back.” We may find beaver activities expensive and annoying at times. On other occasions we greatly appreciate their work. Wherever we are, we must admit they are beautiful animals, wonderfully designed to follow their own agenda. Canada’s national emblem is characterized by skill, initiative and lots of energy. It’s fun to watch them in action. Aren’t you glad they live in our country?
Moxie’s challenge: Make a list of beaver design features and discuss who their Creator is. Can you think of any creatures which are not perfectly designed for their particular lifestyle?
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