All About American Beavers

Nature's hydroengineers, American Beavers, present several challenges.

| March/April 2011

Beaver Dam

Beavers use sticks, branches and mud to build lodges in which to live, where they are protected from predators. Dyer

As I approached the five-wire electric fence that protects my grapevines in a remote three-acre field, I immediately knew I had a problem. The characteristic “tick, tick, tick” of the charging circuit was noticeably silent. Knowing that heavy weeds or errant brush can sometimes cause the fence to ground out, I started walking in search of the problem. As I rounded a corner of the field that borders a slough, I found the source of the short. A 20-foot poplar tree was lying across the fence pinning all five wires to the ground. Because we hadn’t experienced any severe weather recently, I was completely perplexed until I glanced at the base of tree and noticed the telltale chew marks of a beaver.

I was aware that there was a small beaver colony on my property. Occasionally I would hear the loud “slap” of a tail on water or catch the sight of a beaver swimming across the slough, but this was the first time they had caused me any problems. Higher than normal water levels were allowing the beavers access to trees near my fences and outbuildings. After spending an afternoon cutting up the fallen tree and retightening my fence, I decided to research my options for dealing with future problems and also to learn a little more about beavers.  

Beaver basics

The American Beaver is actually the largest North American rodent. It is found throughout the United States and Canada, with the exception of extreme northern Canada, the deserts of the Southwest, and most of Florida. According to the book, Beavers, by Wil Mara, the beaver’s large orange teeth are capable of chewing through a 6-inch tree in 15 minutes. With a flat, paddle-shaped tail that serves the dual purpose of acting as a rudder in the water and aiding in balance on shore, the beaver is well equipped to survive in an aquatic environment. Adding to its water-capable makeup, the beaver’s nose and ear valves shut when it submerges, and a thin membrane covers its eyes serving as a type of goggle to protect the eye from irritation. It also has lips that close behind its front teeth, enabling it to carry a branch in its mouth without drowning and protecting the beaver from swallowing any splinters of wood while gnawing through a tree. The front feet of a beaver are short and equipped with claws useful for grooming and packing mud, and the rear feet are webbed, which enhance its swimming ability. The beaver’s lung capacity is also quite amazing, allowing it to stay underwater for up to 20 minutes without resurfacing for air.

Beavers may grow to a length of 5 feet, but 3 to 31⁄2 feet is more typical. They can weigh as much as 90 pounds, with the average adult beaver typically between 40 and 50 pounds. Their coat is composed of long, coarse guard hairs over a thick undercoat and ranges in shades of brown.

Community creatures

Beavers mate when they are 2 years old. The mating season runs from November to March. Young beavers (kits or pups) are born in May or June, with an average litter of three to four. Beaver babies weigh less than a pound and have the ability to follow their mothers underwater before they are a day old. Young beavers stay with their parents for two to three years. After the first year, the parents will have another litter –
only one litter per year – and the young from the previous year will actually help care for the newborn kits. Typically, after a third year at most, beavers are “kicked” out of the colony and forced to find their own mate and territory. 

Saved from the brink

The beaver’s thick, luxurious coat or “pelt” is what led to the near extinction of the beaver population in the United States in the last century. As early as the 1500s, the beaver was trapped for its fur, which is strong, warm and has the natural ability to shed water. Hats, coats and collars made from beaver were popular and led to a worldwide demand for pelts. Much of the Westward expansion in the United States was predicated on the relentless pursuit of new and more productive beaver populations for trapping. When Europeans first came to America, it was estimated that the beaver population was anywhere from 150 million to 200 million animals. By the early 1900s, the beaver had disappeared from most of its range across the central United States. It was about this time that the public became concerned about the animal’s extinction and enacted trapping regulations, and live trapping reintroduced beavers across much of their original range. Today, the beaver population is estimated around 10 million and continues to hold stable. 

john wilkinson
2/22/2011 5:50:20 PM

The Beaver have intrigued me since I was knee high to a grasshopper. I have trapped them for both relocation and for damage control, so I'm aware of their "busy as a beaver" work ethics. They are also the only critter that is capable of creating their own habitat. I just read the article, it was very informative and accurate. However, the picture on pg. 17, is incorrect. Those are Nutria on the float not Beaver. Nutria were introduced to the U.S. from Argentina in the 60's, where they were raised on a farm for their fur. Unfortunately, they escaped and now have become very devastating in the coastal marshes in Southern states.

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