by R. D. Stevenson
Dept. of Biology, University of Massachusetts Boston, Boston MA 02125
Susan Abruzzi
Teacher, Paul F. Doyon Memorial School, Ipswich MA 01938
Table of Contents:
Traveling southbound on interstate 95 through the town of Newbury, Massachusetts, approximately ten miles south of the New Hampshire border, we noticed a wide, watery channel just down the embankment. This channel was too wide to have been engineered by the highway department and too wet to be a seasonal wetland filled with skunk cabbage. A closer inspection, accomplished by getting out of the car, revealed a beaver colony. Who would have thought? Upon reflection, the signs were clear but the context so unlikely that the obvious conclusion was not made. Having made the observation that the beavers had built a channel parallel to the highway, we were no longer surprised by the sight of a dead beaver several miles farther down the road.
The channel spreads over several miles between Route 1 and I 95, and the sun shines down on the rippling water, causing reflections that resemble smoke rings to dance up and down the newly submerged tree trunks. For the waterfowl, turtles, and otter that have recently discovered this rich habitat, it’s a welcome signal. However, for the people who live around this newly formed wetland, these rings seem to serve as a warning for flooded basements and roads, unsafe drinking water, septic system issues, and of trees being felled, as yards quickly become the town’s newest pond.
The colonization of interstate highway property and suburban communities by beavers is a clear indicator of the tremendous recovery of this ecologically important species, but it also suggests how beavers' activities can bring them into conflict with humans. In this paper, we will provide some background information about the name and natural history of the beaver, discuss its ecological role as a keystone species, review its historical relationship with people in New England and discuss the current controversies surrounding the beaver's impacts on human-dominated landscapes. Throughout history, beavers have been a harbinger of the changing role of human attitudes and relationships with the environment. We suggest that proactive management techniques and willingness by humans to share the Commonwealth would greatly reduce human-beaver conflicts. At the end of the article is a list of contacts if beavers have become a "nuisance" in your neighborhood.
The beaver's common name comes from the Anglo-Saxon word "beofor," meaning brown (Rezendes 1999). A quick check of the US Government’s authoritative Integrated Taxonomic Information System (ITIS) http://www.itis.usda.gov/itis_query.html), using "beaver" with the Animalia and vernacular options selected, tells us that the scientific name of the North American beaver is Castor canadensis. Click on the scientific name and the database returns the taxonomic hierarchy including the beaver’s family, Castoridae, and order, Rodentia. Because of the beaver’s great economic importance during the Europeans’ invasion of North America that began in the 1600’s, it is surprising that the beaver did not get its scientific name until 1820 when Kuhl wrote the taxonomic description. If one returns to the initial query page of ITIS, it is possible to learn about the genus Castor, by typing in "Castor", and checking "scientific names" before submitting the query. The genus was bestowed by Linnaeus in1758, when he applied the name Castor fiber to the European beaver, a larger animal and only other extant congener of our species. Both sexes of beavers possess musk glands that produce a liquid, castoreum, used for scent marking by the beavers and collected by humans for making perfumes. The word "castor" is also associated with castor bean oil from the seeds of Ricinus communis (Euphorbiaceae), a star in the constellation Gemini, and the twin in Greek mythology (http://daphne.palomar.edu/wayne/plmar99.htm). Despite the connections we have not been able to uncover why Linnaeus christened the beaver Castor.
The fascinating biology and habits of the beaver, North America’s largest rodent, are well known to many adults and children. Elementary school students learn that beavers build dams and can make a mounded home out of logs and mud; that they cut down trees with their large incisors; and that they use their paddle-like tail to slap the surface of the water to communicate danger to others in the colony. These primarily nocturnal animals have several other intriguing adaptations that enable them to thrive in an aquatic environment.
One such feature is their built-in waterproofing lotion. Beavers waterproof their fur by using an oil that is secreted from their anal glands (Pennsylvania Game Commission 2001, Ryden 1989). This oily substance is rubbed over two different types of hair that grow on their bodies: the coarse guard hairs, and a shorter under fur. It is the under fur that provides insulation during the colder weather, and it was this finer hair that the trappers so ferociously sought during the fur trade. On the second toe of each webbed, hind foot, beavers have an extra claw or a special pincer claw which helps with grooming (Ryden 1989, Snell).
Beavers have valvular ears and nostrils that automatically close when swimming. They also have a nictating eye membrane that protects their eyes while they navigate through their murky underwater world. While submerged, beavers have an amazing ability to close their mouths behind their four large incisors, allowing them to carry and chew foods underwater without drowning (Ryden 1989, Pennsylvania Game Commission 2001). In addition to their well known tail-smacking behavior, beavers use their tails as rudders. Their webbed feet help to propel them through the water. All of these features enable beavers to stay underwater for a period of fifteen or twenty minutes (Ryden 1989, Pennsylvania Game Commission 2001).
Beavers locate most of their food by using their keen sense of smell (Pennsylvania Game Commission 2001). Herbivores, their choice foods include birch, willow, aspen, and alder. Beavers also feed on a variety of aquatic plants including pond weed and water lilies, especially the rhizomes. Like other rodents, beaver have orange incisors, which are kept sharp by a hard outer layer of enamel and a softer dentine inside. The incisors are deeply embedded in their jaws, and grow continuously throughout the beavers' lives. Incisors must be constantly worn down which the beaver accomplishes by grinding them together or by chewing. Symbiotic microorganisms living in their cecums digest up to 30% of the cellulose material (Findley, J.S. 1987. pp. 85f-88 cited in LTER data 1998).
Beavers are territorial animals, often marking areas around their lodge with scent mounds. Found close to the water's edge, these mounds usually consist of leaves and other debris that are brought up from the bottom of the pond. Scent mounds are marked with the beaver’s castoreum which, often upon close inspection, can be detected. It is uncertain just what these scent mounds are communicating to other beavers. Some researchers suspect that these mounds are used to communicate a variety of messages, depending on whether the oil secretion is from the beavers' anal or castor glands (Ryden 1989). It has been suggested that beavers' territorial behaviors will actually limit population density (Nolet and Rosell 1999).
Beavers have a complex family structure, and are often observed by researchers as being quite affectionate with each other. Beavers have, on average, three to four kits per year and take great care to raise their young. Beaver young usually stay with the family unit for one to two years, with yearlings often taking an active role in helping to raise new kits (Ryden 1989).
More information about the natural history of beavers can be found at:
Beavers turn small streams into ponds and wetlands, thereby altering biota and ecosystem processes and augmenting nature's services, which makes them one of the most important "keystone" species in North America. Beavers create habitat for themselves and a host of other species. As with all ecological disturbances there are winners and losers. Upland trees such as pine become flooded and die, while new habitat is created for willows. Lotic (of moving water) aquatic insects disappear but lentic (of still water) species can thrive. Overall, beaver wetlands create greater standing stocks and major shifts in aquatic insect, plant, amphibian, fish, and waterfowl assemblages (see references in Snodgrass and Meffe 1998). Along with the biotic changes, ecosystem processes are also altered. Water, nutrient and carbon availability, cycling and dynamics are all affected (see references in Snodgrass and Meffe 1998). With regard to natural services, beavers' eco-engineering prevents downstream flooding, reduces erosion and facilitates the creation of new soil.
At the landscape level, the amount of flooded area of beaver ponds depends on the topography. In regions with low relief such as Minnesota, beavers might flood as much as 13% of the landscape (Johnston and Naiman 1990, cited in Lisle 1999) whereas in Maine only 1.5% of the landscape was modified (Lisle 1994, cited in Lisle 1999). Even a pond that covers only 1.5 % of the landscape can draw wildlife from a wide area.
The impact of beavers as agents of ecological restoration has not been documented in New England or in Massachusetts. Their impact must be sizable due to both the unique habitat they create and their population, which is estimated to be over 50,000 individuals in Massachusetts. In Western North America, one can imagine that the ponds built by beaver would have even a greater impact on wildlife because they would provide a local water supply in the drier seasons.
People’s interactions with beaver are deeply rooted in the history of our county. Beavers were very important to First Nation peoples in New England (Spiess 1992, Eckstorm 1926, and Speck 1992 cited in Lisle 1999) as they undoubtedly were throughout most of the continent (Mills 1990). By the time the first European explorers arrived in North America, the European beaver (Castor fiber) had been extirpated across parts of Europe due to the demand for beaver pelts that were primarily being used in the hat industry (Outwater 1997). Beaver fur was the fur of choice for this industry because of the small barbs at the ends of each hair, which enabled them to interlock and make a felt fabric. See http://www.whiteoak.org/learning/furhat.htm.
With the discovery of a land filled with beaver and the strong market demands back in Europe for beaver fur, the trapping of beaver in North America led to one of the first great natural exploitations in the United States and Canada (Outwater 1997). Beavers were to Canada as cod were to Massachusetts. Legendary companies such as the Hudson Bay Company (1670), North West Company (1783), and the American Fur Company (1808) were established primarily for the fur trade, and in particular to trade and sell beaver fur. The beaver trade became a means of procuring goods for Native Americans that they otherwise would not have been able to obtain. Tribes became dependent on these goods, and as a result, changed the ways in which they harvested the natural resources in their area. Beaver pelts became an accepted form of currency. Several companies marked their blankets with points, small lines woven into the fabric, to denote how many beaver pelts one would need to trade to obtain the blanket.
During the peak of the fur trade era some 200,000 pelts a year were sold to the European market. In Massachusetts, William Pynchon had established a trading post in 1636 along the Connecticut River Valley with the main commodity being beaver pelts. By the 1650’s, the beaver trade in Massachusetts was described by Pynchon as being of "little worth". Yet, from 1652 to 1658 Pynchon’s son managed to procure 9,000 beaver pelts. See http://www.meer.org/chap2.htm.
As areas were trapped out, trappers would go farther north and west to find untapped areas. This continued across our country until the early part of the 19th century, when beaver numbers were dismally low, and the demand for fur in Europe was reduced by the popularity of silk hats.
Efforts to restore beaver to the Commonwealth of Massachusetts were not begun until the early part of the 20th century. In 1932, the Beaver Protection Bill was approved, giving complete protection to the beaver. Twenty years later, however, responding to complaints, the legislature authorized a winter trapping season (Kirk 1999). Since then, problem beavers have been trapped by licensed trappers. In November of 1996, the Massachusetts Wildlife Protection Act (WPA) was passed. This act prohibited any person from placing, maintaining, or manufacturing any trap for the purpose of capturing fur bearing mammals, except for common mouse and rat traps, nets, and box or cage type traps that are otherwise permitted by law. 
As a result, a ubiquitous wildlife practice that had been used for years was removed as an emergency solution for beaver related issues. Since the WPA became law, the Division of Fisheries and Wildlife estimates that beaver populations have risen in the state to 60,000 with a carrying capacity of 100,000 (Cole 2001). With populations on the rise, beavers are returning to areas in which they had not been present for years--creating dynamics that are as interesting to watch as the latest hit show. In Peabody and Acton, there have been very public discussions; in Newbury, dams have been breached and beaver shot with little notice. How these dramas are played out often relies upon the willingness of the players to embrace beavers as neighbors.
In July 2000, the 1996 trapping law was changed, in what is known as the "Beaver Bill". It authorizes local Boards of Health to issue permits to individuals when beaver activity threatens the public health and safety within a community. With emergency permit in hand, an individual can build a water flow device to reduce flooding, breach the dam, relocate the animals using a box or cage trap, or kill the beaver with a Conibear trap. In the first two instances, permission from the Conservation Commission is also needed because of the wetlands alteration; for trapping a person licensed by the State Fisheries and Wildlife Division must be hired. Additional permits can be obtained from the local Conservation Commission and the Division of Fisheries and Wildlife if the work is not completed in 10 days.
People and beaver in the 21st century: interactions, attitudes, economics & educationIn Massachusetts, New England, and much of the continent, humans and beavers have conflicting visions of the landscape. Human populations are growing and people are opting for single family homes in commuter communities located on the outskirts of Boston and other urban centers. Recovering from three centuries of over exploitation, beaver populations are growing, too, and beavers are opting for single family homes in first order streams, wetlands, and even along the Interstate 95. Most clashes occur in low lying areas where humans are creating suburbia and beavers are creating dams.
You can read about the problems in newspaper stories http://www.s-t.com/daily/04-96/04-17-96/5beaver.htm, at 2nd annual New England Indian Regional Environmental Training Conference http://www.ntec.org/reports/region1day1.html, in reports from the Humane Society http://regions.hsus.org/nero/downloads/2000%20NERO%20Spring.pdf. or in news articles about towns in Massachusetts (Brosnahan 1999, Aubrey 2001, Wyner 2001 and Wandzilak 2001).
In Massachusetts alone there are hundreds of complaints per year. Most often, the comments are that "beaver are a nuisance" and that "there are too many beavers". People and towns suffer property damage and spend lots of money fighting beavers. Human communities feel as though they’ve been invaded. From the beavers' viewpoint many of the same argument might be made. We hear the beaver spirit calling, "We are an oppressed race reclaiming our lost land."
Beavers can damage plantings and timber (Härkönen 1999) as well as impede the migration of fish, but the greatest economic impact seems to be for road work where beaver damming has plugged a culvert and rising water washes away a road. When beavers are removed, they usually return in 1 to 3 years and the drama is replayed. Over time this can cost hundreds of thousands of dollars.
In the last ten years a variety of techniques (beaver deceivers and beaver bafflers) have been developed to reduce the conflict between humans and beavers. When they work, water flow devices appear to be the most effective solution to manage beaver. The cost to trap beavers is $200 to $2000 and will only last until the next beaver moves in. The cost of water devices ranges from $500 to about $1500, and they provide a better long-term solution. With such large cash outlays, it is not surprising that people with experience say that unwanted beavers are often killed in disregard of the law.
As populations increase, both beaver and humans take the best sites first. If one were to ask whether humans are invading good beaver habitat (low lying meadows next to wetlands) or whether beavers are invading good human habitat.(dry upland sites), we think it might be more a case of the former than the latter. Along with barrier beaches -- another example in which people love the location, but the habitat is subject to such large disturbances -- low, wet areas should be avoided by humans as a place to build.
Living with beaver requires tolerance, skillful management and vision; a vision to support and enhance the biodiversity of our earth for all of the species that reside upon it. It requires a commitment on behalf of a community to embrace the idea that beavers are a valued natural neighbor. As a step toward reducing conflicts between humans and beavers, we advocate that scientists use GIS techniques to map potential beaver dam sites. Such information in the hands of local planning boards and conservation commissions would allow all to be more proactive in anticipating conflicts. Because most people lack focus about the natural world and because of the strong drive to protect private investments, it seems unlikely that the outcomes of human and beaver conflicts will change radically in the short term. Perhaps, as management techniques improve and people come to grips with population issues, we will achieve a less violent relationship with this remarkable species.
Anderson, Rebecca. 2000. Castor canadensis, European Beaver. Animal Diversity Web, Museum of Zoology, University of Michigan. http://animaldiversity.ummz.umich.edu/accounts/castor/c._canadensis$narrative.html.
Aubrey, Scott. January 20, 2001. Littleton. Beavers have residents, Water Department concerned about Flooding. Community Newspaper Company. http://townonline.com/northwest/littleton/02605766.htm
Brosnahan, Michelle A. 1999. Ban on trapping opens flood gates to beaver damage. Community Newspaper Company. http://townonline.com/realestate/professionals/beaverflooding.html
Cole, Caroline Louise. 2001. Beaver Boom, State Law Leaves Residents Trapped. Boston Globe 5/13/2001, p.W16.
Eckstorm, F.H. 1926. History of the Chadwick Survey from Fort Pownal in the district of Maine to the Province of Quebec in Canada in 1794. In Sprague’s Journal of Maine History, Vol. 14.
Findley, J.S. 1987. The Natural History of New Mexican Mammals. University of New Mexico Press, Albuquerque. pp. 85-88.
Härkönen, S. 1999. Forest damage caused by the Canadian beaver (Castor canadensis) in South Savo, Finland. Silva Fennica 33(4): 247—259. http://www.metla.fi/silvafennica/abs/sa33/sa334247.htm
Harris, Noah. 1996. Castor fiber, European Beaver. Animal Diversity Web, Museum of Zoology, University of Michigan. http://animaldiversity.ummz.umich.edu/accounts/castor/c._fiber$narrative.html#contents.
Hudson, Roy. 2001. Beavers in trouble everywhere. Natural New England March/April 2001 6:40-44.
Jackson, S. and T. Decker. Beavers in Massachusetts. 1993. University of Massachusetts Cooperative Extension Service and the Massachusetts Division of Fisheries and Wildlife, CR-0333-9/93. 17 pp. Free at http://www.umass.edu/umext/nrec/pages/biodiver_pub.html
Johnston, C.A., and R.J. Naiman. 1990. The use of a geographic information system to analyze long-term landscape alteration by beaver. Landscape Ecology 4:5-19.
Kirk, William. 1999. Leave it to the Beavers: Two species of Obsessive Dam Builders are Coming into Conflict on the Floodplains of Suburbia. Sanctuary, Massachusetts Audubon Society, March/April 1999)
Lisle, Skip. 1994. Beaver recolonization in south-central Maine. M.W.C. thesis. University of Maine Orono.
Lisle, Skip. 1999. Penobscot nation methods to control damming by beavers. Draft manuscript (Penobscot Nation Wildlife biologist. Dept of Natural Resources, 6 River Road, Old town Maine 04468. )
Mills, Enos A. 1990. In Beaver World. University of Nebraska Press. 234 pp. Originally published by Houghton Mifflin Co. 1913.
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Pennsylvania Game Commission. 2001. Beaver. http://sites.state.pa.us/PA_Exec/PGC/pubs/w_notes/beaver.htm
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Sevillete LTER data. 1998. Data: Species: Mammal: American Beaver - Castor canadensis. http://www.findarticles.com/m2120/n3_v79/20608564/p1/article.jhtml
Snell, David. Canadian Beaver. http://www.csh.rit.edu/~snell/beaver.html
Snodgrass, J.W. and G.K. Meffe. 1998. Influence of beavers on stream fish assemblages: effects of pond age and watershed position. Ecology 79:928-942. http://www.findarticles.com/m2120/n3_v79/20608564/p1/article.jhtml
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Spiess, A.E. 1992. Archaic period subsistence in the New England and Atlantic provinces. In Early Holocene Occupation in Northern New England. Pp.162-185. edited by B.S. Robinson, J.B. Petersen and A.K. Robonson. Maine Historical Commission, Augusta Maine.
Wandzilak, Nadine. April 26, 2001. Reading Busy ‘lil beavers. Community Newspaper Company. http://townonline.com/northwest/reading/11007833.htm
Wyner, Michael. February 15, 2001 Acton. Beaver control, trapping alternatives aired. Community Newspaper Company. http://townonline.com/northwest/boxborough/05983083.htm
If you have a beaver problem, try these people. They have experience with both the animals and the politics.
Beaver Solutions. Mike and Ruth Callahan, Owners
98 Bay Road
Hadley, MA 01035-9688
Phone: 413-585-9145 Fax: 413-587-9788
email: mrcallhn@aol.com
http://www.shawsheen.org/Beavers/beavers.html
Stephanie Hagopian
Massachusetts Society for Prevention of Cruelty to Animals
MSPCA Department of Advocacy
617-522-7400
http://www.mspca.org/advocacy/issues_answers/advo_ia_masswildlife.htm
Skip Lisle, Penobscot Nation, Phone Number: 207-827-7776. slisle@penobscotnation.org
Skip Hilliker, Connecticut, East Hampton tel. 860-267-0061
http://fund.org/library/documentViewer.asp?ID=81&table=documentsAll photographs by S. Abruzzi, ©2001. Photographs cannot be reproduced without permission of photographer