Introduction to Beaver
Beaver, the largest North American rodent. Beavers also are found in parts of Euope and Asia. Beavers live in woodland ponds, lakes, and streams. They are related to the gopher, marmot, chipmunk, and squirrel.
Beavers use their sharp teeth to cut down trees.North American Beavers live mostly in the Rocky Mountains and in northern Canada. Scattered colonies are also found near Lake Superior and in Maine. Due to extensive trapping their range has been reduced. However, they have been reintroduced in some areas and the populations are thriving.
Facts in brief about beaversNames: Male, none; female, none; young, kit or pup; group, family or colony.Gestation period: About 3 months.Number of newborn: 2 to 4.Length of life: About 12 years.Where found: Asia, Europe, North America.Scientific classification: Beavers make up the beaver family, Castoridae. The North American beaver is Castor canadensis. The European beaver is C. fiber.The Body of the Beaver
A full-grown beaver is about 30 inches (76 cm) long—not counting the tail—and weighs 35 to 60 pounds (16 to 27 kg); unusually large beavers sometimes weigh 110 pounds (50 kg) or more. The animals have small, rounded heads, small ears that can be closed when swimming, and powerful jaws. The body is thick-set; its back is humped. The forelegs are short with handlike paws that can be used to handle sticks and logs. The hind legs are much larger and permit the beaver to sit erect. The webbed toes on the hind feet make the animal a powerful swimmer.
How Big Is a Beaver?The beaver is the biggest rodent in North America. An adult beaver is 3 to 4 feet (91 to 120 centimeters) long from its head to the end of its tail. The animal weighs from 40 to 95 pounds (18 to 43 kilograms).
Thousands of years ago, beavers were even bigger than they are today. Some were nearly 8 feet (2.4 meters) long. Scientists are not sure why beavers have become so much smaller.
A beaver’s back feet are 6 to 7 inches (15 to 18 centimeters) long. Each foot has webbed toes with strong, split claws. The webbed feet work like flippers to make the beaver a strong swimmer.
How Is a Beaver’s Fur Helpful?A beaver’s fur is helpful in many ways. For example, it is so thick that it can protect the beaver from insect bites and pointy sticks.
Fur also helps a beaver in the water. A beaver can waterproof its fur by combing in its body oil with its claws. Once the fur is waterproof, it helps keep the beaver warm as it swims.
Fur keeps a beaver comfortable in cold weather, too. The fur traps body heat underneath. It acts like a blanket to keep the beaver warm, even in freezing weather.
Fur also helps a beaver stay safe. Its brown color lets the beaver blend in with trees and bushes. That way, beavers can hide from their enemies.
The beaver's teeth are used to cut down trees needed for food as well as for dams. There are two cutting teeth, or incisors, in each jaw. They are curved with chisellike cutting edges, capable of cutting through trees two feet (60 cm) thick. Although the tips are worn away by constant gnawing, the teeth remain approximately the same size because they continue to grow throughout the animal's lifetime.
What Makes a Beaver a Rodent?A beaver, like all rodents, has four incisors. A beaver has two incisors in its upper jaw and two in its lower jaw. Beavers use their incisors to gnaw.
The front of each incisor has a very hard orange coating. The back of each incisor is much softer. It wears down faster than the front. As a beaver gnaws, this difference in hardness allows each incisor to form a sharp edge, like the edge of a chisel.
Incisors are not a beaver’s only teeth. A beaver also has 16 back teeth that are used for chewing.
In between a beaver’s front and back teeth is a long gap. In this gap are flaps of skin that actually separate the front and back of the animal’s mouth. This helps a beaver gnaw wood without swallowing splinters. A beaver can also gnaw in a pond without swallowing water. If this rodent wants to eat or drink, it just opens its skin flaps.
Beavers have two sharp incisors in each jaw.The beaver's broad, flat, scaly tail is 8 to 12 inches (20 to 30 cm) long. Shaped like a canoe paddle, it is used as a rudder in swimming. The first beaver to see an approaching enemy sounds an alarm by slapping the water with its tail.
What Is Special About a Beaver’s Tail?A beaver’s tail looks somewhat like a boat paddle. It is about 12 inches (30 centimeters) long and 6 to 7 inches (15 to 18 centimeters) wide. The tail has scaly skin and almost no hair.
A beaver’s tail is quite useful. In the water, it helps the beaver steer while swimming. On land, the tail supports the beaver when it stands up to eat or cut down trees.
A beaver’s tail also comes in handy as a storage space. It stores body fat that supplies the beaver with energy when food is hard to find. In addition, the tail stores two body oils. The beaver uses one oil, castoreum (kas TAWR ee uhm), to mark its territory. It uses the other oil to waterproof its fur.
The tail serves as a defense weapon, too. If a beaver senses danger, it slaps its tail hard on the water. The loud noise warns other beavers in the area to take cover.
Life of the Beaver
Beavers are most active at night. They feed mostly on the inner bark of hardwood trees that grow near lakes and streams. The animals usually live in family groups called colonies. These typically consist of 12 beavers (often a pair and their last two litters), in several homes.
The beaver's home, or lodge, is built in the water or on the bank of a pond, lake, or stream. The lodge is a hollow mound of sticks plastered together with mud. The room inside, which serves as living quarters for the family, is above water level and has an air hole in the top. The lodge has thick walls that protect the animals from weather as well as from enemies. Its entrance is a tunnel that opens under water. Some beavers store twigs and branches for winter food in a second room dug under the first. Others store their food in an underwater pile near the entrance to the lodge.
Beavers dam streams and ponds to keep the water deep around their lodges at all seasons of the year. The entire colony works on these dams, the largest of which are sometimes 1,000 feet (300 m) long and more than 10 feet (3 m) high. The animals use their sharp teeth to cut down trees and shape the logs. The pieces are then dragged into the stream and laid in layers in the mud, which anchors them. Mud, stones, and branches are packed among the logs. As the dam raises the water level, more material is added at the top.
Why Do Beavers Build Dams?A beaver dam is a wall of sticks and stones in a stream. The dam traps water flowing downstream. Behind the dam, a pond forms. The pond is still and deep—the perfect place for a beaver home. The pond is also a place to store food and to hide from enemies.
Building a dam keeps beavers very busy. Often a whole family works together to build the dam. The beavers begin by pushing rows of sticks into the stream bed. Then they pile rocks and mud onto the sticks to weigh them down. Later, the beavers push tree branches and grass between the sticks. They add more mud so that water cannot flow through the sticks.
It usually takes two to three days for beavers to build a dam. When it is finished, the wall of sticks is high. The top of the dam rises above the water. Beaver dams can be very long, too. Most stretch between 16 and 96 feet (5 and 30 meters) across.
What Is a Beaver Lodge?A lodge is a home that beavers build in a pond. The lodge is made from the same materials as the dam—sticks, rocks, and mud. The top of the lodge rises 3 to 6 feet (91 to 180 centimeters) above the water. It has a shape like a cone and looks a little like a tepee.
The lodge has several underwater tunnels and entrances. All of them lead to a main indoor room, or chamber. The chamber floor is 4 to 6 inches (10 to 15 centimeters) above the water. The chamber keeps baby beavers warm and dry. It is also a place where parents dry off after bringing food to their babies.
Beavers take good care of their lodge. They add to it and fix it often. Some beaver lodges last as long as 30 years.
Beavers mate for life. A litter consists of up to eight young, or kits, which weigh less than one pound (450 g) at birth. The young remain with the parents until they are nearly two years old and are carefully trained to take care of themselves. In their natural environment, beavers live 10 to 12 years; in captivity, sometimes nearly 20 years.
What Do Baby Beavers Look Like?At birth, baby beavers look just like their parents, only smaller. Baby beavers are called kits or pups. Newborn kits are about 15 inches (38 centimeters) long from their heads to the ends of their tails. They each weigh 1/2 to 1 1/2 pounds (0.2 to 0.7 kilograms). Beaver kits have thick fur, sharp teeth, and open eyes. They can see, hear, walk, and swim immediately.
Before baby beavers are born, the other family members get the lodge ready. They work closely together to do this.
The mother carries her babies inside her body for three months before giving birth. She has two to four babies at a time. Usually they are born in April or May.
What Is Life Like for Beaver Kits?Like all mammals, baby beavers drink only their mother’s milk at first. They swim for the first time inside the lodge. They’re too young to waterproof their own fur, so their mother does it for them.
After one month, the kits can leave the lodge. The mother shows them how to find food and escape from enemies. The kits learn by doing what she does.
As kits grow, they play together. They wrestle and chase each other. They also dive and swim. All this exercise helps make their muscles stronger.
After one year, the young beavers are ready to start working. They cut down trees and help build and fix the dam and lodge. They also help their parents care for their newest brothers and sisters.
Young beavers live at home for about two years. Then they must go off on their own. In time, they each find a mate and build a new lodge.
Importance of Beavers
Beaver fur is highly valued for its softness and durability. Much of North America was explored by trappers seeking beaver pelts for export to Europe. In colonial times, beavers were found throughout North America as far south as central Mexico. After years of unlimited trapping, the animals disappeared from much of this area. It became necessary to protect those remaining by laws limiting trapping to a short season.
Certain glands in the beaver's body produce castoreum, a material like musk used in making perfume and also as a lure in wild animal traps. Beaver dams help hold runoff water, reducing the danger of floods and aiding soil conservation.
What Do Beavers Like to Gnaw?Beavers love to gnaw trees. They eat the inner bark, twigs, roots, and leaves. A beaver’s favorite trees are poplars, aspens, cottonwoods, willows, and birches. One acre of trees can feed a family of six beavers for more than a year.
Like most rodents, beavers are herbivores (HUR buh vawrz). That means they eat mostly plants. They eat many shrubs in the spring and summer. They also like to eat water plants such as water lilies.
Beavers plan their meals carefully. In the fall, they store food for the winter. They cut trees into small pieces. Then they stick the wood in mud underwater near their homes. In the winter, they swim under the ice and eat the wood they have stored.
What Keeps a Beaver Busy?Beavers seem to be at work all the time. They are often busy gnawing down trees. Beavers eat some parts of the trees and use other parts to build homes. Beavers cut trees even after they have a home and plenty of food. Scientists don’t know why beavers like to do so. But one reason may be to keep their incisors from growing too long.
Cutting down a tree takes time and hard work. First, the beaver bites the trunk in two places. It keeps biting into both cuts to make them deeper. Then it pulls off pieces of wood between the cuts. After doing this many times, the tree is ready to fall. Before the tree crashes down, the beaver runs for safety, often diving into water.
After the tree falls, the beaver returns to work. It gnaws off the branches. Then it pushes, pulls, or carries the log into the water. The beaver stores some of the branches in the water for food to eat during winter. It uses other branches to build or fix its home.
Who Are a Beaver’s Enemies?A beaver’s most dangerous enemy is the otter. An otter can swim into a beaver lodge through the underwater tunnels. Inside, the otter often attacks weak and helpless beaver kits.
On land, a beaver has many more enemies. They include coyotes, wolves, foxes, and bears. Other enemies, such as hawks, eagles, and owls, may not attack an adult beaver, but they will go after the kits. A beaver keeps from danger by staying in water a lot. It comes out at night to eat or work. But even then, it stays alert for signs of enemies.
If a land enemy comes near, a beaver will slam its tail down. It does this to warn other beavers of danger. Then it hides, either by going underwater or to an escape hole it has dug on land. The hole has a tunnel that leads to water. If cornered, a beaver will fight with its sharp teeth.