Northern Prairie Wildlife Research Center
DISTRIBUTION: Found throughout North Dakota, especially along the larger streams and rivers and in the Turtle Mountains. Not as abundant in the prairie pothole region of the state.
There are two sub-species of beaver in North Dakota. The Canada beaver (Castor canadensis canadensis) is found largely in the eastern and northeastern part of the state and in the Turtle Mountains. The Missouri River beaver (Castor canadensis missouriensis) is found in the Missouri River and its tributaries. The Canada beaver is somewhat more valuable due to its darker coloration, slightly larger size, and better quality fur. Beaver movements and transplanting have caused the original ranges of the two sub-species to overlap and crosses between the two are found in many areas.
HABITAT: Beavers are water dwelling animals. They prefer streams with an abundance of trees and brush with which they can build dams to control the water level.
LIFE HISTORY: Beavers pair for life and are monogamous (males mate with only one female). They breed in February or March and the young are born three months later in May or June. They may have from one to eight young. The usual litter contains from two to four. The young beavers remain in the nest for five to six weeks. They remain in the lodge of their parents for two years. Then the parents send them out on their own. These young beavers usually follow the stream to an unsettled area, find mates and build their own dams and lodges. Beavers have lived as long as nineteen years in captivity but it is very doubtful if many reach that age in the wild.
The average beaver weighs about thirty pounds. Just about every year some exceptionally large beavers are caught, weighing as much as seventy pounds. One of the largest beaver ever caught was taken near Lancaster, Wisconsin in April, 1960. It weighed ninety-two and one-half pounds.
Beaver are both nocturnal and diurnal (active during the day) but are most active during the late evening and at night, especially if they live near human habitations.
The beaver does not hibernate. During the fall they build a large store of food near their lodge. This food pile, which is placed in the water, is known as a beaver cache. As both the cache and the beaver's entrance to the lodge can be reached from under the ice, the beavers do not need to come out above the ice during the winter. Beavers build dams to insure a water depth sufficient to enable them to live safely and comfortably at all times. They cannot breathe under water, but they can stay under for long periods of time and can work under water without fear of drowning.
They build their lodges and dams out of whatever material is readily available. They usually use sticks, brush, and mud but also use aquatic plants and grasses, especially if no woods material is available. Beavers almost always build lodges if materials are available and water conditions are favorable. If materials for lodge building are scarce, or if the stream is too large and swift to dam, they will live in dens dug in the bank.
FOOD HABITS: Aquatic plants, twigs and bark of aspen, cottonwood, and willow are preferred but beavers will eat the twigs and bark of most kinds of deciduous trees and small shrubs and brush.
SUGGESTED BAITS: Fresh twigs and cuttings of aspen (poplar) preferred. Fresh cottonwood or willow twigs and branches.
SUGGESTED LURE INGREDIENTS: Beaver castoreum collected from the musk sacs (or "castors") of the beaver is a basic ingredient of almost all beaver lures.
The beaver is a big, strong animal and you must keep this in mind when trapping them. Do not use small traps as the beaver will pull out of them, and will become trap wise and much harder to catch. When trapping beaver, plan your sets so that the beaver will drown. The surest way to do this is through the use of a drowning wire. In shallow water it may be necessary to wrap the trap chain through the spring of the trap to eliminate slack which would enable the beaver to reach the surface.
Some trappers place sticks in deep water so the trap chain will wrap around them. This method will work as the weight of the trap will eventually tire the beaver out, but it is not as fast nor as efficient as the use of a drowning wire. Another method of making drowning sets is to tie a rock to the end of the trap chain. The beaver pulls the trap and rock into deep water and drowns.
The fur of a beaver becomes prime during the winter and is at its best in late winter and early spring. This means that most beaver trapping must be done through the ice. Fortunately, during this period beavers are attracted to bait and this makes them relatively easy to trap under the ice.
Bait sets under the ice are made along the beaver's travel lanes from their lodge to their food cache. It is wise to locate these cache and houses and pick out good trap sites before freeze up as this is much more difficult to do when everything is covered with ice and snow. Twigs and small branches of aspen and cottonwood make the best bait but willow and birch may be used.
One of the easiest and most effective under-ice beaver sets is the "pole" set. Take a pole of dry wood and nail or tie green aspen to it for bait. Place a trap on the pole (tie it in place with string) about a foot below the bait with the trap chain secured to the pole below the trap. Place the pole through a hole in the ice and push it firmly into the mud until the bait is about six inches below the bottom of the ice. Nail a crossarm to the end of the pole sticking up through the ice so that the beaver cannot pull the pole under the ice.
The pole set can be modified in many ways to suit various conditions. Small dry sticks can be nailed to either side of the pole to hold the trap in a horizontal position. Some trappers use two small poles in place of one larger one and nail crossarms across for the bait and trap. You can also use boards in place of poles and push the board in at an angle much like the leaning-board set used in trapping muskrats.
In shallow water it is often possible to place the trap on the bottom of the pond. Cut a hole in the ice in the shape of a "U" about two feet long. Build a cubby of dried sticks with one end stuck in the bottom of the pond and the other sticking up through the hole in the ice. Build the cubby in the shape of the "U" with the opening about one foot wide. Place the fresh bait in the closed end of the cubby so the beaver has to cross the trap (or traps) to get at the bait. Attach a wire to your trap and run it in behind the cubby logs, up through the hole in the ice and fasten it to a crosspiece of strong, dry wood. Push the ice and slush back into the hole when you are done as this will hold the cubby sticks in place until the ice refreezes.
When making any under-ice sets for any species be sure that you have some method of retrieving your trap and catch. This can be done by securing your trap to a pole or by leading a long wire attached to the trap chain up through the hole in the ice and securing it to a cross-piece.
When spring is near and the ice shows signs of weakening, pull up your under-ice beaver sets. Otherwise, you might lose your traps when the ice goes out.
After the ice is out, beaver can be caught in a variety of water sets. Blind sets are effective if you find a place where the beavers have been going up on shore. Set your trap about six inches deep and use a drowning wire on your trap.
Blind sets can also be made where beavers have been going up onto their dams and are especially efficient where there is a small break in the dam. Set your traps on the upstream side of the dam. Traps set on the beaver's house may scare the beavers and make them harder to catch in your other sets. Beavers can also be caught by setting traps at the entrances to their bank burrows.
In the spring of the year, beavers are especially attracted to fresh bait. Find a spot in water from four to eight inches deep near where the beavers have been active. Construct a cubby of dried sticks in the shape of a rough "V" and place some freshly cut bait of aspen or cottonwood twigs as the head of the cubby. Place your trap so that the beaver has to cross it to get the bait. As the beaver swims with its front feet folded in at its sides, there is a chance that it will spring the trap with its belly. Place a small branch near the center of the cubby and place your trap just to one side and slightly back of this branch. When the beaver strikes this branch with its stomach, it will stop swimming, and as it settles down to eat, a hind foot should come down upon the trap.
When trapping beaver, the good trappers always plan for a hind foot catch. A beaver caught by a front foot will often twist its foot off in the trap unless it drowns first. Try to picture the beaver as it swims up to your set, as it finds the bait, and as it settles down right about "here", so that is where you set your trap.
Beavers often use scent mounds along the shore. These are mud piles upon which the beavers deposit some of the secretion from their castor glands. Artificial scent mounds can be made by heaping up a little pile of mud and placing a few drops of beaver castoreum for lure on the mound. They can be used for beaver sets simply by placing traps at the bases of the mounds. If these mounds are near the water's edge use a drowning wire.
Sometimes it is necessary to make dry land sets for beaver although you should stick to water sets if possible. Unless a humane type trap is used in dry land beaver sets, you should use a multiple trap set with the idea of trying to catch the animal in more than one trap to prevent its escaping. Space your traps so that no part of one trap can touch the pan of another. This will prevent a trap on the beaver's foot from springing another trap. Cover the traps, chains and stakes with dried grass, leaves or moss.