Leave it to beaver

On a very cold morning last month, I sat in a well-concealed hide near a small, wooded pond. It was quiet and still there, just off the Cooper River, and the first hints of daybreak had begun coloring the eastern sky. Suddenly a loud “pop” nearly jolted me off my stool. 

 

Though it still startled me, I had heard the sound before. As the noise was being repeated several times my eyes searched the still-dark pond, and at last I found the source. A dark form was silently making a small wake through the water. It headed towards the nearby bank, eased through some tall reeds and was gone. This protesting beaver had made it very clear that I had intruded too close to her lodge. These tail slaps are a beaver’s alarm signals, and they can be heard and recognized from quite far away.                                                                                                    

Castor canadensis, the American beaver, is sometimes called the North American beaver or the Canadian beaver. These beavers inhabit most of North America and, through human introduction, a small part of South America. Paleontologists have identified beaver fossils as far north as Ellesmere Island, in the high arctic, dating from much warmer times some 3 million years ago. They have been here a very long time.

 

The American beaver is a “keystone species.” Keystone describes a species that can fundamentally change entire ecosystems by itself. I was reminded of that fact recently in another pond where I saw some of the damage a local beaver family had done in an amazingly short period of time. In less than two weeks, and probably in just a few days, a beaver or beavers chewed through and felled a tall, healthy tree, which appeared to be a swamp chestnut oak, about a foot and a half in diameter. In no time these industrious rodents had killed what took decades to grow and mature. There is a great YouTube video, “Why do Beavers Build Dams? Nature’s Engineers” by Real Wild. It details how man’s introduction (or reintroduction) of beavers into a given area largely saved the Elk Island National Park in Alberta, Canada, but is also threatening to destroy the natural balance of Tierra del Fuego.

 

Beavers inhabit freshwater swamps and ponds, especially with moving water. Their lodges are conspicuous mounds of wood, brush, etc. and have underwater entrances for protection. Beavers eat the bark and cambium from the trees they fell and use much of the rest in their construction projects. They have several adaptations, like their self-sharpening teeth, their nasal and ear valves for diving and their third eyelids for underwater vision, that make them very good at what they do.

 

Young beavers will live with their parents for a couple of years while learning their trade and helping with the dams and lodges. Then they will move on, find their mates, and build dams and lodges of their own. They can live as long as 20 years in the wild.