The Beaver

Without beaver fur, the fur trade might never have existed. The fur of the beaver had unique qualities that made it a good choice for felt hats and helped sustain a fashion for almost 300 years. To understand the process of making a felt hat, you might want to check out the section on beaver hats.

Today, after almost 400 years of trapping, the beaver is abundant, and in many places there are so many beaver they are considered a nuisance. The northeastern corner of Minnesota is one of the places where the beaver is once again thriving. For those who travel the same lakes and rivers used by the voyageurs, the beaver dam and beaver lodge are common sites. In fact, it is almost impossible to travel a small stream without encountering numerous beaver dams which force you to drag your canoe and equipment over the branches and mud used to construct the dam. In the evening as you sit at your campsite, beaver are often seen swimming. Always busy, they seem like workmen heading off for the “night shift”. In the early morning they can often be seen heading back toward their lodges after a busy evening of feeding and building.

Where they live

Water is the most important factor in the daily life of the beaver. They can manage poor food conditions much better than a lack of water. Beavers cannot survive where water levels fluctuate too much from season to season or if the water is fast moving. If you want to find beavers, look for stable water levels in lakes, streams and rivers. They prefer ponds, small lakes with muddy bottoms and meandering streams.

beaver fur hat, fur tradeBeavers never venture far from the water. They build their lodges (homes) on the water (islands) or next to the water and must have an exit directly to the water. If the water level drops, the beaver will extend its lodge or dig a canal until it is possible to create an underwater exit. If the water level isn’t deep enough, it will relocate. Dams the beaver builds often have the effect of increasing water depth. Rather than travel across land, a beaver will seek to dig a canal between two water sources if they are relatively close together. When they live in a northern climate, the water must be deep enough to allow them to leave the lodge through an underwater exit even during the winter when the lake or stream might have a thick layer of ice.

A natural swimmer and the slap of the tail

The beaver’s tail is used for balance when it is on land, but the beaver is basically a clumsy and slow moving animal on land. It would easily fall prey to the wolf, fox, bobcat and others.

The slap of a beaver tail is very loud. It sounds like someone doing a “cannonball” into the water and is easily mistaken for a large rock or tree falling into the water. They slap their tails to warn other beavers of danger, to frighten enemies and to make an enemy reveal its location by startling it.

In the water however, it is a sleek, torpedo shaped swimmer. The front feet are tucked under the chin. The webbed rear feet provide powerful swimming skills and the tail is used for maneuvering. The beaver has a nictating membrane that protects its eyes underwater. Both its nostrils and ears close automatically when its nose touches the water. It has fur lined lips and features in its mouth that prevent water from entering its wind pipe.

The prized beaver fur is well adapted for an animal that spends all its life in dark, damp and humid places. The underfur (the layer prized for making hats), is thin, soft, wavy and very dense. The color usually ranges from black to gray. The external guard hairs are stiff, thick and long. The guard hairs serve to keep dirt and water from reaching the underfur. When a beaver dives, a layer of air is captured in the fur next to the skin to help provide insulation.

Beavers can stay underwater for as long as 15 minutes. This is because they are very good at using the oxygen in their lungs. They may be able to use as much as 75% of the oxygen in comparison with about 15% for humans. They also seem to be able to increase the oxygen flow to their brain, tolerate high levels of carbon dioxide and reduce their heart rate when diving.

The slap of a beaver tail is very loud. It sounds like someone doing a “cannonball” into the water and is easily mistaken for a large rock or tree falling into the water. They slap their tails to warn other beavers of danger, to frighten enemies and to make an enemy reveal its location by startling it (remember the slap is LOUD). The beaver may even slap its tail to play. When really frightened however, beavers usually skip the tail slap and quickly swim away. Although it is not known why, females are more likely to slap their tails than males.

What they eat

Beavers are strictly plant eaters (herbivores). When feeding on shore, they try to stay close to the water’s edge. When possible, they will build dams to increase the depth of the water to increase the shoreline. They will also dig canals to allow water to flow to new feeding areas. The beavers front teeth are constantly growing. The outside surface is very hard while the inside layer is relatively soft. As the beaver chews on hard bark, the inside layer wears down faster than the outside. The result is a very sharp, chisel like tooth, well suited for stripping bark and chewing through wood. Beavers keep the front teeth sharp by grinding them together.

Beavers cut down trees to eat the bark. They also eat leaves, woody vines, some types of grass and shrubs. They eat pond plants including lillie pads. In the north woods they prefer the trembling aspen tree if it is available. They store food supplies underwater for the winter. It has been noted that beavers will often cut down trees that they do not enjoying eating. It appears that they often use these trees and branches for their building activities.

How they live

Beavers live in family groups rather than colonies. Beavers are monogamous (one male and one female are a breeding pair). The family may have adult children, but usually only one pair is actively breeding. The young, called kits, are born with their eyes open, fully furred, have teeth and can swim and walk within minutes of birth. However, it takes them a long time to fully develop and become independent. It is typical for kits to remain with the parents for more than a year.

Beavers tend to avoid each other outside of the lodge. However, kits depend on adults and yearling kits for survival, getting food, building and maintaining the lodge and dams and for establishing the winter food bed during their first summer and winter. For these reasons, keeping the “family” together is very important.

Beavers tend to move around mostly at night during the summer months. During the winter in the north country, beaver may spend months living under the ice, never venturing on to the shore. They survive on the food supplies stored in the food bed.

It is not known exactly how or why new family groups are formed. Kits may leave the home lodge before they are a full year of age or stay until they are almost three. When they do leave, they may travel several miles in order to find a new living place. Sometimes whole families will move together when food supplies become poor.

Most beaver activities like building dams and houses, digging, moving materials and storing food in the fall seem to be “instinctual”. Beaver raised in isolation show the same patterns of behavior as animals living in the wild. Building dams is a particularly strong behavior pattern. It appears that it is “motivated” by the sound of running water. That is, beavers build dams to minimize the sound of flowing water. The effect of increasing water depth is a consequence, not the reason. One scientific study actually found beavers building a dam against a wall in a dry room when they played the sound of running water through a loud speaker in the wall!

The beaver lodge is a complex structure composed of sticks and mud. Besides its underwater entrance, each lodge has a vent hole in the top. Lodges generally provide excellent insulation during the winter months. A study of beaver lodges in Alaska found that the inside temperature of a lodge never got below 25 degrees (fahrenheit), even though the outside temperature dropped as low as 49 degrees below zero!