Canadian Projects: Beavers
The beaver is Canada's national emblem, taking the role played by the bald eagle in the United States. But it is not for anything like the same reason. Beaver were instrumental in the early European exploration of Canada due to the value of their pelts to Europeans. The felt-top hats, like the one worn by the Mad Hatter in John Tenniel's illustrations of Lewis Carroll's famous Alice in Wonderland books, were the vogue in 19th century England, and beaver pelts were used in their production. The demand resulted in the fur trade extending its tentacles throughout wilderness areas of what is now Canada. The lustrous fur continued to be favored in fashion well into the 20th century.
When beaver pelts were greatly in demand, wildlife management officials always claimed that the take by trappers was "sustainable" and did not diminish the populations. Now that demand (and subsequent value of beaver pelts) has significantly decreased, beavers are becoming more common and are reappearing in areas where trappers had previously wiped them out.
Beavers still have not reached historical numbers, but their presence has caused some conflicts with human interests. One major concern is that beavers can cause flooding by blocking water flow, including the movement of water through culverts. The water can back up and flood crops and even rural roads.
There are numerous devices that can mitigate against such situations. One is to keep beavers away from culverts so they cannot block water flow, which they do to create ponds large enough and deep enough to accommodate their "lodges" — elaborate structures of interwoven sticks and branches that provide chambers for raising their young, with underwater entrances to avoid predators.
Apart from blocking culverts, beavers also will construct elaborate dams across streams to form ponds, and can also cause unwanted flooding. In such cases tube piping placed through the dams can allow humans to control the depth of the pond to reduce or eliminate flooding. Both these methods tend to be more effective, and at times more cost-effective in the long term than trapping or shooting the beavers and are obviously more humane, but often local authorities know nothing about them or have no idea how well they work.
Beavers, when not persecuted, are not especially shy around people. They can move into suburban and urban areas, where their habit of gnawing through trees and felling them to use their branches for food and for construction of dams and lodges can create conflicts. Some of the trees chosen by beavers may have been planted, and valued, by the human community. However, such trees can be wrapped in heavy gauge wire that protects them, thereby allowing beavers to focus their attention on less-valued, fast-growing species such as poplars. Again, education and persuasion are essential. Too often the first and only response to such conflicts is to get rid of the beavers. Educating humans is important, ongoing work.
One of the most serious charges levied against beavers is that they are a source of disease, specifically giardiasis, popularly called "beaver fever." It is caused by a type of parasite that can be found in the intestines of various species, including humans. It usually is transmitted via infected water, and thus beavers, muskrats and other aquatic species often are blamed for its presence. But the term "beaver fever" is a misnomer, and recent research shows that it is usually human fecal matter that first contaminates the water, thus infecting the mammals living in the habitat, rather than vice versa. Studies show that the greater the use of water by humans, especially for recreational activities, the greater the likelihood of waterborne giardiasis being present.
It should also be noted that we are ever more aware that beaver ponds provide valued ecological and social functions. Ecologically they provide breeding habitat for a wide range of other wildlife species, including ducks, frogs and fish. But also they help to protect water sources and combat droughts by maintaining higher water levels and protecting wetlands. This has become of particular importance in recent years due to an increase in regional droughts. Two biologists, Glynnis A. Hood and Suzanne E. Bayley, reported in Biological Conservation in 2008:
"Shallow open water wetlands provide critical habitat for numerous species, yet they have become increasingly vulnerable to drought and warming temperatures and are often reduced in size and depth or disappear during drought. We examined how temperature, precipitation and beaver (Castor canadensis) activity influenced the area of open water in wetlands over a 54-year period in the mixed-wood boreal region of (the western Canadian province of) Alberta. This entire glacial landscape — with intermittently connected drainage patterns and shallow wetland lakes with few streams — lost all beaver in the 19th century, with beaver returning to the study area in 1954. We assessed the area of open water in wetlands using 12 area photo mosaics from 1948 to 2002, which covered wet and dry periods, when beaver were absent on the landscape to a time when they were well-established. The number of active beaver lodges explained over 80 percent of the variability in the area of open water during that period. Temperature, precipitation and climatic variability were much less important than beaver in maintaining open water areas. In addition, during the wet and dry years, the presence of beaver was associated with a ninefold increase in open water area when compared to a period when beaver were absent from those same sites. Thus, beaver have a dramatic influence on the creation and maintenance of wetlands, even during extreme drought. Given the important role of beaver in wetland preservation and in light of a drying climate in this region, their removal should be considered a wetland disturbance that should be avoided."
In providing such information by one community, municipality or region at a time, we have made inroads on protecting Canada's beavers from persecution, but it is a continuing, uphill battle against ignorance — and against indifference to the plight of this magnificent animal.
Learn more about Coexisting with Beavers — no matter where you live — with our helpful brochure.