Outdoors: Beaver dams have many benefits to ecosystem

Courtesy Photo/Mary Gayle SartwellBeaver dams make great trout ponds like this one I am fishing on the Hermosa Creek in Durango, Co.

I stood on the edge of the beaver dam and cast a #18 blue dun out into the deep channel that marked the creek bed that flowed along the far shore. Although now covered with about six feet of water, this channel was where I hoped to find a trout or two. Nature’s best engineers had built a beautiful pond on the upper reaches of the Parker River. 

It is hard now for folks to imagine how important the beaver was to the exploration of this continent. Just as Salem, Boston and New Bedford were once the whaling centers where fortunes were made, the profits from the sale of beaver pelts to Paris, Rome and London generated profits that created some of the largest real estate holdings ever known on this continent. Wave after wave of trappers, traders and explorers spread out across the United States and Canada in search of the beaver.

It is his fur that made him desirable to man. It is hard to describe how soft and luxuriant a fully tanned beaver pelt is beneath your hand. The long dark guard hairs cover a wonderful, incredibly thick, lighter brown under fur that made it the most popular skin for outer garments before man-made fibers were invented. It was waterproof, warm and beautiful. If you wore a beaver coat and were covered with a buffalo robe, you were comfortable in the surrey or sleigh.

There is no doubt that the beaver (castor canaensis, for you Latin fans) is the master mechanical engineer of the animal kingdom. He is a nonstop builder that can create some of the most elaborate and strong dams that are able to hold back vast quantities of water. I have seen dams in Canada that are a quarter of a mile wide and that have created back-ups a mile long. 

These ponds are created solely to provide the beaver a safe environment in which to live. They build a domed lodge made out of mud, branches and twigs that has a large dry and warm  central living area above the level of the water. The only way in and out of the structure is under water which prevents predators from entering their home. It is also above the ice level which allows oxygen in during the winter. 

In the spring of the year the young beaver separates from his family and heads off on his own. He locates an area where young poplars grow as this is their main food source. He then seeks out a relatively flat spot in the brook and starts a dam.

It is amazing how quickly they can stop up the flow of water. Where there was once a quick flowing stream, they can create a small pond of several feet deep. 

Over time these dams slow the speed of the creek. The deposits in the water sink to the bottom, making for an incredibly rich soil that grows lilies and other water-dependent vegetation. Other wildlife such as ducks and geese soon make these small impoundments their homes and breeding grounds as well. Trout find places to hide in the new growth and feed on the insects that thrive in the environment. A whole new little ecosystem develops.  

Upstream from their freshly constructed dam, the beaver begin to build a new house. Although relatively modest to start, these houses, over time, can grow to become huge structures. And as the new arrivals find a mate, they need to create space for the youngsters that will follow

The pair breed in January or February and the youngsters will be born in March or April. The litter will range anywhere from two to six with the average about four. The kits will weigh in at a hefty pound each,  fully furred and eyes wide open which is quite advanced in relation to other wildlife.  For example, a black bear cub at birth only weighs six to eight ounces, is blind and relatively hairless. 

The young are soon eating the tender bark of the poplar and playing around the pond. These little fellows are built to live in the water. They have five toes on each foot, but the back feet are completely webbed making them great engines for swimming.  When they dive below the surface they can close their nostrils and ears so no water will get in. They also have a see-through membrane that they can lower over their eyes. It  acts like a pair of goggles so they can see very well under water. They can hold their breath up to fifteen minutes so, when alarmed, they can swim all the way to their lodge and go up through the underwater entrance to safety. 

As an adult a beaver can grow up to sixty or so pounds and be over four feet long. Their teeth are a very bright orange and continue to grow their whole life. The only thing that keeps them short is the wear from constant gnawing on wood. The tail is large, flat, and nearly hairless. It is used as a rudder in the water and a prop when it stands up on land. He has a thick layer of body fat that keeps him warm in the cold water. He keeps that hair waterproof by covering it with castoreum which is an oily secretion taken from its scent glands.

The dried testicles of the beaver were used as early as the ninth century in the Middle East and Europe to relieve pain. The willow tree, which the beaver eats, contains salicin. The castoreum transforms this into salicylic acid which is similar to aspirin. Native Americans ate the willow bark to relieve pain, but the concentrated amounts in the beaver testicles worked better.  This castoreum is also used to this day in the manufacturing of perfume.

As the dams fill up and the food sources diminishes, they are then forced to abandon their dam and lodge and move on to new territory where the process starts all over again.

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