Species accounts

Eurasian beaver

Castor fiber

TAXONOMY

Castor fiber Linnaeus, 1758, Sweden.

OTHER COMMON NAMES English: European beaver.

PHYSICAL CHARACTERISTICS

Weight 33-75 lb (15-35 kg). Yellowish brown to black fur and a flat tail. Has longer nasal bones, larger and more massive skull and smaller tail than the North American beaver. The anal gland secretion is a thick paste of a grayish color in females but oily with a whitish or pale straw color in males. It is brown and viscous in male but it is whitish or light yellow and runny in female North American beavers. Eurasian beavers are significantly more resistant to tularemia.

DISTRIBUTION

Formerly distributed continuously across Eurasia from the British Isles to eastern Siberia. Presently, established throughout Europe except for Iberia, Italy, and the southern Balkans. Present also in China, Mongolia, and Khabarovsk.

HABITAT

Common to freshwater wetlands, rivers, streams, lakes, ponds, and even bogs.

BEHAVIOR

Nocturnal, but more diurnal (especially at dusk) if undisturbed. Territorial throughout the year. Tends to live in burrows and is less likely to construct dams than the North American beaver. Mark tufts of grass, rocks, and logs, as well as directly onto the ground.

FEEDING ECOLOGY AND DIET

In spring and summer, particularly aquatic plants, and a wide range of grasses, forbs, ferns, shrubs, leaves and twigs, crops, bushes and trees in fall, and twigs and bark in winter. Tree preferences are aspen, poplar, and willow.

REPRODUCTIVE BIOLOGY

The Eurasian beaver matures later and has smaller litters (average 2-3 kits; maximum 7) than the North American beaver. Monogamous.

CONSERVATION STATUS

Overhunting reduced Eurasian beaver populations to about 1,200 animals, in eight isolated populations around the end of the nineteenth century. Protection, natural spread, and reintroductions led to a powerful recovery in both range and populations during the twentieth century, which continues at a rapid pace despite considerable loss and degradation of habitat. The minimum population estimate is 593,000 in 2002. The Eurasian beaver is protected under Appendix 3 of the Convention on the Conservation of European Wildlife and Natural Habitats and is listed as Lower Risk/Near Threatened by the IUCN.

SIGNIFICANCE TO HUMANS

In Eurasia nearly all beaver-human conflicts are caused by beavers feeding on cultivated plants, or dam building. They are

Wetland Keystone Species

keystone species in wetland habitats, and humans increasingly acknowledge their environmental contributions. Hunting and dead-trapping are allowed in the Nordic countries, Russia, and Baltic countries. Presently, beaver safaris are offered to observe beavers in Norway, Sweden, Poland, and France. ♦

North American beaver

Castor canadensis

TAXONOMY

Castor canadensis Kuhl, 1820, Hudson Bay, Canada.

OTHER COMMON NAMES English: Canadian beaver.

PHYSICAL CHARACTERISTICS

Weight 33-75 lb (15-35 kg). Yellowish brown to black fur and a flat tail.

DISTRIBUTION

Historically located throughout the continental United States, the subarctic of Canada to the tundra and northern Mexico, excluding desert regions and southern Florida. Presently, beavers are found in most of these areas but in lower numbers. Successful introductions in Finland, Russia, and Argentina.

HABITAT

Nocturnal, but more diurnal (especially at dusk) if undisturbed. Territorial throughout the year. Tends to live in burrows and is less likely to construct dams than the North American beaver. Mark tufts of grass, rocks, and logs, as well as directly onto the ground.

BEHAVIOR

Alters the landscape more with extensive dams than the Eurasian beaver. Scent marking occurs almost exclusively by creating mud mounds. Otherwise, behavior is similar to the Eurasian beaver.

FEEDING ECOLOGY AND DIET

Strict herbivores, prefer the cambium and leaves of soft wooded trees like aspen (Populus). However, incorporate a wide range of food items into their diet such as aquatic plants, herbs, grass, shrubs, conifers, and deciduous hardwoods.

REPRODUCTIVE BIOLOGY

As for the Eurasian beaver but mature earlier and has larger litters (average 3-4 kits; maximum 12). Monogamous.

CONSERVATION STATUS

In the late twentieth century, population estimates were 6-12 million, probably less than 10% of historical levels. Beavers have no special status although in some regions it is illegal to tamper with their dams.

SIGNIFICANCE TO HUMANS

In past centuries, the Canadian beaver was an important animal for the First Nations and is part of Native American myths and folklore. The Apaches endowed beavers with the magic powers of the medicine men and they are also part of the folklore of European settlers. Much of the exploration of North America was also a result of the search for beavers, highly prized because of the value of their pelts. In the latter half of the twentieth century, the poor economic value of beavers has assisted the recovery of many populations. Beavers provide enormous ecological benefits as well as recreational and aesthetic value. They probably affect their immediate environment as much as humans. The greatest environmental change results from their dam-building activities. The damming of streams raises the level of the water table. Several tree species cannot survive in waterlogged soil and their death allows the spread of species that are adapted to permanently wet soil. These include for example, willows, cottonwoods, and alders. Beaver ponds are a favorable habitat for many forms of life: insects lay eggs in them, fish feed on the insect larvae, and muskrats, mink, shore-birds, and fish thrive. There are over 50 species of animals that live in beaver ponds. ♦

Resources

Books

Busher, P. E., and R. M. Dzieciolowshi. Beaver Protection, Management and Utilization in Europe and North America. New York: Kluwer Academic Plenum Publishers, 1999.

Conley, V. A. The War Against the Beavers. Minneapolis: University of Minnesota Press, 2003.

Novak, M., J. Baker, M. Obbard, and B. Mallock, eds. Wildlife Furbearer Management and Conservation in North America. Toronto: Ashton-Potter Limited, Ontario Ministry of Natural Resources, 1987.

Owl, Grey. Tales of An Empty Cabin. Toronto: Key Porter Books, 1999.

Periodicals

Halley, D., and F. Rosell. "The Beaver's Reconquest of Eurasia: Status, Population Development and Management of a Conservation Success." Mammal Review 32 (2002): 153-178.

Wilsson, L. "Observations and Experiments on the Ethology of the European Beaver (Castor fiber)." Viltrevy 8 (1971): 115-266.

Organizations

Arkansas Soil and Water Conservation Commission, Beaver Conservation Program. 101 East Capitol Avenue, Suite 350, Little Rock, Arkansas 72201 USA. Phone: (501) 682-3953. Fax: (501) 682-3991. Web site: <http://www.state.ar.us/ aswcc/page6.html/>

Bruce A. Schulte, PhD Frank Rosell, PhD

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