Beaver
Builder of Dams and Fortunes
While untold bounties of codfish first lured Europeans to return regularly to the northern shores of America, it was the beaver that beckoned them into the continent. With the European beaver becoming virtually extinct, visiting fishing vessels in the 1500s inadvertently tapped into a luxury market in beaver pelts, which natives on the shore were only too happy to trade for metal tools and implements. Both the beaver’s abundance and the density of its soft inner fur, which it needed for warmth in frigid waters, made it more important to humans than any other furbearer. In the days before umbrellas, upper-class heads were kept fashionably dry with broad hats of beaver felt. Mercury, used to separate the fur from longer guard hairs and to break it down into felt, frequently caused mental deterioration among the ranks of ungloved hatmakers, giving rise to the expression “mad as a hatter.”
The British, Dutch and French chartered state monopolies to secure the northern forests’ fur bounty in the early 1600s. Indeed, the Pilgrims of Plymouth were far more grateful at their Thanksgiving feasts for the beaver than the turkey, with the lucrative profits from fur-trading posts established in the Maine interior primarily responsible for keeping their colony afloat. Similarly, New York City was founded when beaver-pelt-seeking Dutchmen bought Manhattan Island from the natives as a base. The Dutch, though, centered their fur trading just south of the Mohawks’ great hunting and trapping grounds in the Adirondacks, at Albany, where 60,000 beaver pelts a year were soon flooding in.
Even the opulence of modern New York’s Waldorf-Astoria Hotel was ultimately founded upon the humble beaver and John Jacob Astor’s American Fur company, which established trading posts from the Great Lakes to the Pacific in the early 1800s. Astor invested his fur money in New York City real estate and became the richest man in the United States, with a fortune of more than $25 million when he died in 1848.
But the fur rush blazed a trail of ecological and social upheaval across the continent. Before the coming of white traders, woodland natives followed sustainable economies, fine-tuned through millennia, with each family’s traditional hunting and trapping territory defined by a watershed. Families rotated their activities, from one river branch to another within the basin, ensuring that beavers and other animals they hunted could rebuild their populations in each area.
The aboriginal system was disrupted by the steel-age goods and technology of Europeans. Metal pots, axes, guns, and blankets offered huge time-saving advantages and luxuries, but hooked Native Americans into a European market economy, while they lost their own complex survival technologies. Traditional family trapping grounds were quickly exhausted to satisfy the new demands for fur. Both natives and traders pushed farther west. The Iroquois, seeking control of the trade routes, nearly wiped out, drove off, or absorbed the Mahican, Huron, Erie, Neutral, and many other nations in the Beaver Wars of the 1600s. A chain reaction of disruption spread across the continent until, by the late 1800s, there were few beavers, but much dependency.
Luckily, beavers were one of the first animals to benefit from the efforts of the early conservation movement. They were given legal protection and reintroduced or spread on their own into the largely beaverless north woods in the first decades of the twentieth century. Today’s New York State beavers are largely descendeants of immigrants brought from Michigan. Small refugee populations in Maine, Minnesota, and Wisconsin were also used to restock much of the country.
Both beavers and people are driven by the urge and ability to change and control their environment. A native tradition holds that the Creator took the power of speech away from beavers to keep them from becoming superior to humans. The Ojibwa said that beavers could change form into other animals. They were highly respected and an important food source, especially their fleshy tails.
Beavers form essentially matriarchal societies. According to some experts, when one- to two-year-olds leave home for good, females choose their mates for life and determine where they will live. If her partner dies, the female recruits a replacement and life goes on. If a matriarch dies, however, the colony usually breaks up. After mating in the water, beneath the ice, in January or February, mothers give birth sometime between late April and early June. Newborns are fully furred, and their eyes are open.
Beavers—the largest rodents in North America—can go to work wherever there is a stream and an ample supply of deciduous trees, especially aspen. If the water is shallow or intermittent, they build a dam, creating a reservoir deep enough to swim and dive in safety, one that will not freeze to the bottom in winter. The inundated area, often covering ten acres (four hectares) or more, is like a farm, growing the succulent water plants beavers eat in the summer. As well, it’s a conduit for reaching and transporting felled hardwoods. Wherever the ground is soft, beavers may dig thin, shallow canals and tunnels into the woods and across peninsulas.
By controlling the water level, beavers ensure their lodge will not be flooded out or left high and dry by seasonal watershed fluctuations. A pair of beavers can build a dam in three or four days, with branches stuck diagonally into the mud so that the wall slopes downstream, braced against the force of the constrained water. Beavers scoop up mud with their paws to fill in the structure once all the branches are woven in place. They often build a series of dams along a stream, sometimes reaching up to 10 feet (3 meters) high.
Beavers in a well-established colony may not be busy at all during the relatively carefree days of spring and early summer. They are active mostly from dusk to dawn, occasionally warning each other to dive for safety with a loud tail slap on the water when danger approaches. From September until freeze-up, the colony works hard to build up a winter food supply of branches, extending their nocturnal toilings into the day. Beavers are often on land in this period, standing on their hind feet, propped up by their tails, cutting down trees. They cannot control where a tree falls, but heavy growth on the tree’s sunny side usually topples it toward the water. A winter’s larder of tasty trunks and branches, piled and sumbmerged beside the lodge, may equal more than 1,000 cubic feet (30 cubic meters).
Flooded areas behind beaver dams become swampy, often creating rich habitat for a succession of plants and animals. After perhaps several generations, beavers may use up all the young broad-leaved trees they can safely reach and desert the area. Their dams slowly deteriorate and the ponds drain, leaving behind rich, silty soil that becomes a meadow. Eventually, the forest reclaims the spot. If fire later sweeps through, the aspen and birch that commonly sprout afterward are usually large enough within five to ten years to support another colony of beavers searching for a new homestead.
Beaver Facts:
TIME IT TAKES A BEAVER TO CUT A TREE THAT IS 5 IN (12 CM) THICK: 3 minutes
THICKEST TREE EVER RECORDED CUT BY A BEAVER: 4 ft (1.2 m)
AVERAGE ANNUAL NUMBER OF TREES CUT BY AN ADULT: More than 200
AREA OF ASPEN FOREST NEEDED TO SUPPORT A COLONY ANNUALLY: 1-2 acres (0.4-0.8 ha)
AVERAGE AREA COVERED BY A BEAVER POND: 10 acres (4 ha)
DAM LENGTH: Average 100-200 ft (30-61 m); up to 5,000 ft (1,500 m) long and 10 ft (3 m) high
LONGEST MEASURED BEAVER CANAL: 750 ft (230 m), in Colorado
AVERAGE ADULT BODY LENGTH: 2-3 ft (60-90 cm)
TAIL LENGTH: 9-13 in (23-33 cm)
WEIGHT: 35-60 lb (16-27 kg)
HEAVIEST EVER FOUND: 110 lb (50 kg), in Wisconsin
MARKINGS: Glossy chestnut-brown body, scaly black tail
BEST SENSES: Smell and hearing
ALIAS: American beaver, Castor canadensis
CALLS: Mumble, hiss, or nasal blowing when angry; cry when frightened
PREFERRED HABITAT: Small, muddy lakes, ponds, meandering streams, and marshes flanked by aspen and birch stands and willow thickets
COLONY TERRITORY: 0.3-1.8 mi (0.6-2.2 km) along a stream or shoreline
HOME: Domed lodge of branches and mud, about 6.6 ft (2 m) high and 13.3-14.6 ft (4-8 m) wide, above waterline, hollowed out from an underwater entrance; built at the center of ponds or at side of deep lakes; occasionally in bank burrows
AVERAGE NUMBER OF BEAVERS PER LODGE: 5-9
FOOD: Water lilies, arrowhead, watercress, duckweed, yellow arum, cattails, grasses, sedges, leaves, berries, and ferns in summer; bark and twigs of aspen, willow, birch, poplar, mountain ash, and maples, and aquatic plant roots in winter
AVERAGE DAILY FOOD HELPING: 1-5.5 lb (0.5-2.5 kg) of bark and twigs in winter; about 12 oz (330 g) of green plants in summer
FORAGING DISTANCE FROM WATER: Usually less than 150 ft (45 m), rarely up to 300 ft (90 m) in wolf-inhabited areas, up to 650 ft (200 m) elsewhere
GESTATION PERIOD: 3 1/2 months
AVERAGE LITTER: 2-4
BIRTH WEIGHT: 0.5-1.5 lb (230-680 g)
AGE AT WHICH YOUNG BEAVERS LEAVE HOME: Usually 1 year; some at 2 years
AGE OF FIRST-TIME BREEDERS: 2-3 years
LIFE SPAN: Average 4-5 years, up to 20 years in wild, 23 years in captivity
PREDATORS: Wolves, rarely coyotes, foxes, mink, and otters
CAPACITY TO HOLD BREATH UNDERWATER: Up to 15 minutes
HEART RATE UNDERWATER: As low as 20% of normal rate
SWIMMING SPEED: Usually about 2.4 mph (4 km/h); up to 6 mph (10 km/h)
TRACKS: Front feet handlike, with 5 fingers, 2.5-4 in (6-10 cm) long; back feet webbed, 5-6.3 in (13-16 cm) long
SCATS: Usually in water, very rarely found, oval, dark brown, sawdustlike pellets, at least 0.8 in (2 cm) long. Nutrient-rich initial droppings are eaten again for full digestion
FAMOUS BEAVER HOT SPOTS: Albany (formerly Beaverwyck; Montreal (Hochelaga, Iroquoian for “where the beaver dams meet”)
NUMBER OF BEAVER PELTS TRADED FOR A MUSKET IN 1700s: About 18
ACCOLADES: Official mammal of New York, Oregon, and Canada
AGE OF OLDEST BEAVER FOSSILS: 35 million years
COMMON BEAVER POND INHABITANTS OR VISITORS: Muskrats, mink, moose, otters, great blue herons, black and wood ducks, mallards, hooded mergansers, woodpeckers, migrant geese, tree swallows, red-winged blackbirds, harriers, frogs, brook trout, minnows
RANGE: Throughout north woods region and at least parts of every other state, north to the tree line in Alaska and Canada
ESTIMATED NORTH AMERICAN BEAVER POPULATION: About 20 million
ALSO SEE: Quaking Aspen, Wolf
© Tim Tiner and Doug Bennet, The Wild Woods Guide: From Minnesota to Maine, the Nature and Lore of the Great North Woods, HarperCollins, New York, 2003
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