Beavers are the largest rodent in North America. Adult beavers average between 3 to 4 feet in length, and weigh between 35 to 70 pounds. Males are slightly larger than females. Because of their size, the only know predators of the beaver are wolves, coyotes, bear, bobcats, and mountain lions. Beavers spend most of their time in the water and have several adaptations for aquatic life such as clear membranes that completely cover their small eyes underwater, valve-like ear and nostril openings, webbed rear feet, a flat tail, and fur that is water repellent and provides excellent, lightweight insulation.
Beavers live in a family colony that consists of a mated pair of adults, one to several yearlings, and juveniles. The average size of a colony in Colorado is 5 individuals, but can range from 4 to 8. The typical lifespan of a beaver is between 8 and 10 years. Females normally do not reproduce until they are 3 years old, have a single litter each year, and the average litter in Colorado is 2 to 5 kits. Mating is monogamous and the adult female is the dominant family member and the leader of the colony. Courtship and mating occurs January to early March, and the gestation period is about 15 weeks. With the birth of a new litter in the late spring, the 2 year old beavers will leave their colony and seek their own territories. They move an average of 4 miles away from home, but not more than 10 miles.
Beavers are born engineers and create their homes using natural materials such as tree limbs, mud, sticks, and grass to construct lodges for shelter and dams to impound water. Beavers need their ponds to be deep enough to hold water year-round and not freeze solid during the winter, usually a minimum of about 3 feet. This construction, especially the dam building, will cause changes to the area they inhabit. These changes increase wetlands, provide the benefits of naturally slowing down and storing flood waters, removing pollutants, increasing nutrients, increasing plant growth, and creates a habitat that attracts a wide variety of waterfowl, insects, fish, and amphibians, especially compared to the unchanged sections of the same creek. Beaver ponds trap sediment and reduce cloudiness, providing clearer water downstream, which is important for native trout.
Beavers feed on plants with non-woody stems, and the bark, buds, leaves, and branches of young aspen, cottonwood, and willow. Most food is taken within 330 feet of the beaver pond, although they have been known to remove trees from 1,640 feet away. Active colony locations are most recognized in the fall, when beavers are cutting trees for their winter food cache. Tree branches are cut and gathered in the fall and submerged in the middle of the pond. The beavers live off this food supply until spring when the pond ice is thawed.
The benefits of increased wetland habitat caused by beavers, especially in dry Colorado, must be balanced against the destruction of trees near home sites. Individual trees can be protected with an enclosure of a heavy wire mesh around the bottom of the tree, with the bottom anchored to the ground so that beavers can not squeeze underneath. Commercial deer repellents have also been used successfully to protect trees from beavers. Providing a limited supply of cut limbs from aspen, cottonwood, and willow, will also help prevent beavers from cutting down existing trees.
With the amount of rain we received last fall, about 16 inches in 6 days according to Dave Lutter’s rain gauge, and the amount of water that rushed down Elk Creek, the wetland area below the ECHPOA pond was flooded, the beaver dam was breached and the beaver pond was emptied. With the loss of our resident beaver, this habit that once attracted moose, heron, ducks, geese and a great fishing pond, will not be rebuilt. I for one would like to bring the beavers back!
To learn more about Beavers, go to the Colorado State Parks Stewardship Prescription: http://cpw.state.co.us/Documents/CNAP/BeaverManagementPrescription.pdf.