The beaver or (Castor canadensis) is north America’s largest rodent. It is the only species of beaver in North America and it’s the world’s third larges rodent (35-80 pounds and up to 3.5 feet in length). The South Americancapybara and the Eurasian beaver are the only rodents larger than the beaver. When described, beavers are often given a geographical adjective such as Canadian beaver, American beaver, or North American beaver; however, they are all the same. In Michigan, beavers are most common in communities with lots of streams or lake chains, such as Brighton, Lakeland, Green Oak, Hamburg, Pinckney, Hell, Gregory, Ann Arbor and Ypsilanti.

Beaver Behavior

Beavers are easy to identify because of their large, unique tails, which are flattened and shaped like the wide end of a canoe paddle. This tail has a variety of uses: as a rudder when swimming, as a paddle to propel them through the water, and as a tool to flatten and pack mud into their dams. Their flattened tail makes the beaver especially suited to the aquatic life; they can truly be described as aquatic rodents and are extremely gifted swimmers. Beavers will spend most of their time foraging along the banks of rivers and streams, and it is here that they are most often sighted. However, if there are no available rivers, beavers will take up residence in any body of water where the banks are suitable for their survival.

Beavers burrow into banks to make their dens. The entrances to these burrows are in a submerged portion of the bank and run up at an angle so the living quarters are deep in the bank above the water level (see Fig. 1). If the dens are built too close to the surface of the ground, they may not have enough overhead support and could collapse or be dug up.  In the winter, when food is scarce, predators such as bears and wolf can dig into the den if it is not far enough underground. The problem is that many banks are not suitable for this kind of excavating. Beavers address this problem by mounding sticks over the den and piling mud on top of the sticks. During winter the the mud freezes, creating a rugged and durable barrier that protects the den.

Fig 1. Beaver Den on the Bank of a River

beaver den illustration

Beavers have built a reputation for themselves as being anything but lazy. Cliches about the beaver’s busyness have become common (“busy as a beaver” or “like a busy little beaver”). A perfect example of the beaver’s industriousness is their construction of lodges. If banks are too shallow for burrowing, beavers will build large, extravagant lodges surrounded by water, commonly referred to as “beaver dams.” These lodges are constructed out of the branches of deciduous trees such as aspen, willow, birch, poplar, and oak. They also use a lot of mud in the construction to protect the lodges against the weather. The lodge serve as a shelter and the bark is their primary food source during the winter. During warmer months, beaver will eat the tender bark on the new growth of trees and shrubs.

When beaver build lodges in rivers or streams, the lodge acts as a dam, raising the water level. This effectively floods out foraging areas, allowing beavers to safely access food without ever having to leave the water. Beavers are most famous for there tireless dam construction. The dams often reach across large expanses of water as the beaver attempt to increase the amount of residual flooding. The largest beaver dam ever recorded was spotted by satellite in Alberta, Canada. The dam was 2,790 feet long and stretched over a half mile (twice as wide as the Hoover Dam). The dams can reach such great sizes because a group of beavers will often form a colony and work together to build tremendously vast damming systems. A beaver colony can consist of up to 20 beavers.

The entrance to the lodge is always submerged  beneath the water’s freeze level. The snow that falls on the dam during the winther insulates the dam and keeps the lodge relatively comfortable, even in the harshest conditions. Beavers, like most rodents, are hoarders who collect and stash large provisions of food for the winter. During the warm months beavers will spend time knawing down trees and shrubs with there front incisor teeth. They will then stab the sharp end of the gnaeed branches into the ground in the water around the dam. The tender bark on the branches will be eaten durring the winter and also serves as great structural habitat for fish.

The beaver’s gnawing  ability is legendary. They commonly gnaw and drop trees up to 2.5 feet in diameter and have been known to drop trees over four feet wide at the base of the trunk. The beaver will often begin a dam by dropping a large tree at the edge of a river or creek. Once the tree has fallen in the water (usually stretching across to the opposite bank) it serves as a foundation and a filter to catch all the rest of the floating debris the beaver will harvest up stream. The beavers work extremely fast and have been known to build dams over night.

A common question people have is how do beavers know when to get away from the tree they are bringing down? Do beavers ever get crushed or killed by the trees they cut down? Beavers do not actually gnaw the trees all the way through. They only gnaw partially, allowing the wind to bring the tree down the next time a little gust blows through, and return to the tree after it has fallen.

Effects on local habitat

Beaver dams are incredibly beneficial for the local wildlife, creating nesting areas for waterfowl, mink, voles, and muskrats. It’s not uncommon for other small mammals to burrow into the sides of the dam (without burrowing into the beavers living chambers directly) and coexsist. Probably the most beneficial aspect of the beaver’s presence is a significant increase in successful spawning of migratory trout and salmon.

Beaver dams filter out harmful sediments and substances that would otherwise destroy the fish eggs in rivers and streams. The dam itself is not the filter,  however; the slow moving water of ponds created by beaver dams allow these substances to settle out and prevent the destruction of the eggs. Interestingly enough, the dams do not form a barrier for fish migration, as larger fish are able to jump over the lower portions of damn and the smaller fish find channels through the innerworkings of the dam. Studies in the state of Washington demonstrate that the presence of beaver dams increase fish spawning success by 89%. Healthy migratory and local fish populations stimulate and abundance of flourishing wildlife that gather to feed off these nutritionally rich and fatty fish as the returning numbers of fish grow exponentially each year.It is worth noting that dams also do not stop the flow of a river; rather, they  temporarily restrict the flow until the water builds up and spills over, under, or though portions of the dam.

Unfortunately, beavers and humans don’t always get along. In regions where beavers are prolific the beaver’s dams threaten downstream property with flash floods and upstream areas are susceptible to flooding or complete destruction of crops, homes, highways, railroads and many other inhabited areas. Other damages include contaminated water supplies, alterations in wildlife habitat, drainage system impairment, chewed landscapes, and trees falling on homes. The assessed economic damage is approximately $1 billion per year in the southeastern United States alone. There are benefits and costs to having a beaver population nearby, and effective beaver control needs to take these both into account.

If you have a beaver on your property, Creature Control has skilled trappers on hand that can apprehend and remove the beaver from your property. It is possible to trap beavers on land, but trapping them in water is much more practical. Whether on land or in the water, beaver trapping is a difficult process, requiring very thorough inspections with special equipment; it can be very laborious and time consuming. It is a process that Creature Control has been extremely successful at. Our skilled technicians have the experience to identify areas of beaver activity and live trap them underwater, upon which they can be safely removed and relocated. If you think you have a beaver, problem call Creature Control today!