Leave It To Beavers

With the exception of man, the beaver is the only creature with the ability to dramatically change its surroundings to suit its own particular needs. And like some environmental changes made by man, the beaver’s alterations can affect other animals, plants, and people enough to require an environmental impact statement. Wherever this largest of North American rodents takes up residence, significant habitat changes soon follow, sometimes causing serious conflicts and consequences.

The beaver – New York’s official state mammal – is an industrious critter and a model of wildlife efficiency. Its untiring work habits and its “waste not – want not” philosophy long ago inspired the phrase “busy as a beaver.” Its daily routine – indeed, its entire lifetime – is spent providing food and shelter for itself and its family. Its cooperative nature and willingness to undertake seemingly impossible tasks are qualities not seen anywhere else in the animal world. Working together, a family of beavers can accomplish remarkable things.

Beavers have to stay busy – there isn’t a lot of choice – because their trademark front teeth, or incisors, never stop growing. These large, curved, orange-colored teeth are positioned so that the top pair overlaps the bottom pair at a slightly different angle. Continual growth and constant gnawing keep the teeth chisel-sharp, enabling beavers to cut down even the biggest of trees. But more important, gnawing keeps the length of the incisors in check. Uncontrolled growth of the teeth could lead to the animal’s eventual demise from starvation. By cutting down trees, beavers acquire a food source – bark and skin from limbs and branches – and building materials for their dams and lodges. Nothing is wasted. And because they can close their lips behind their incisors, beavers can chew underwater. Although beavers will use most any tree, alders, poplars and willows are preferred. An old saying suggests, “Where there are water, poplars, and willows, there are probably beavers.”

Beaver Biology
Beavers are pudgy, rather dumpy-looking animals, not unlike something Disney might have designed – big teeth and all. An adult can range from 25 to 60 pounds and average 3 feet in length. On land it lumbers along with a somewhat awkward gait. Its beady eyes, paddle-shaped tail and oversized hind legs only add to its ungainly appearance. The 12-inch tail is leathery with a scale-like texture. It serves as a rudder while swimming and as a prop when felling trees. Should a beaver become alarmed, slapping the water with its tail produces a rifle-like crack that warns other beavers of the impending threat. Only the hind feet are webbed.

In the water, above or below the surface, the beaver is a graceful and powerful swimmer. Its thick lustrous fur, which nearly brought about its extermination, keeps the beaver warm and dry, even underwater, where it can remain for 10 minutes or more. Like most wild animals that have been antagonized by man over time, the beaver has evolved into a chiefly nocturnal creature.

In the Finger Lakes region, beavers mate annually in February. Litters averaging two to four well-developed kits are born in May or June. Kits weigh about a pound at birth and gain over 15 pounds during their first year. They remain with the family for two years, often helping tend to their younger siblings. After their second winter, sub-adult beavers are forced to leave the colony to seek out territories of their own, making room for their parents’ next litter.

Beavers are vegetarians and will eat plants of every kind. In winter they survive on a diet of tree bark, which is about the only food available, and which they easily digest. Summer diets include a variety of pondweeds, grasses, leaves, mushrooms, fruits and berries. They eat the skin from limbs and twigs, and then stockpile the peeled sticks for use as building materials. They have a fondness for apples and have been known to cut down apple trees rather than wait for the apples to fall. When they have exhausted their food supply – something that may take years – they abandon their work and move on.

Dam Facts
Why do beavers build dams? If you should see a beaver pond, look for a large heap of sticks and mud shaped something like an igloo, piled high in the middle or along the shore. This sturdy structure is a beaver lodge, but unlike an igloo its entrance is underwater. By damming a stream, beavers raise the water level surrounding their lodge enough to submerge the entrance and ensure the security of its occupants. Some beavers, known as “bank beavers,” simply tunnel into a stream bank instead of building a lodge, but entry is still from underwater. Inside of either, living chambers are above water and a small opening at the top provides ventilation. The dam is built just high enough to allow access beneath the ice in winter yet leave the inside high and dry.

The construction of a beaver dam combines the beaver’s engineering skills with the dynamics of nature. Most dams in our area measure less than 50 feet long and 4-to-6 feet in height. In wilderness areas, they can be over 10 times as long and 10-to-12 feet high. Beavers start by pushing sharpened sticks into the mud bottom of any stream having sufficient current to satisfy them. Other considerations include an ample supply of alder, poplar or
willow – perhaps all three. The sticks are jammed together and packed with logs, mud, stones, and anything else available until the water level begins to rise. Leaves, debris and silt drifting downstream become caught in the still-leaky dam until it eventually clogs and stops leaking. I once observed a beaver dam in the Adirondacks that contained a freshly painted dark green picnic bench, which the beavers floated from an island campsite nearly a quarter-mile away.

The Beaver in New York
Like all rodents, the beaver is a prolific breeder, and attempts by New York State Department of Environ­mental Conservation (DEC) wildlife managers to keep its population at manageable levels often prove challenging. Each fall, DEC wildlife technician Martin DeLong conducts an aerial survey to determine the number of beaver colonies in parts of Region 8, and every year they increase. A regulated trapping season is the most effective control available, but because of a declining interest in the trapping of furbearers, population management levels are hardly ever achieved.

This was not always the case. Historically, beaver numbers in New York ranged from overly abundant to nearly extinct, and – with human help – have rebounded. In Beavers: Water, Wildlife and History (Windswept Press, 1991), beaver expert Earl Hilfiker concludes that pre-colonial beaver populations exceeded even “that of the buffalo for which there are estimates of from 60 to 80 million.” By the mid-1600s, when colonization of the New World was earnestly underway, beaver fur was a hot commodity in Europe, mostly for use in making the finest fur felt hats. Colonial explorers, discovering an untouched wilderness of forests, lakes, rivers and streams, also found beavers to be plentiful. The economic potential for stacks of beaver pelts drove England, France, Spain, Portugal and Holland to
wrestle for superiority in the fur trade. Each nation established trading posts with native peoples and dispatched explorer-trappers in an effort to dominate the trade. The awkward and ungainly beaver unwittingly helped to establish a fledgling New World economy.

England and France succeeded in dominating the fur trade; that is why we speak English and the people of Quebec speak French. Indiscriminant beaver trapping initially began along the lower reaches of the Saint Lawrence River with such intensity that before long, the animals were being depleted faster than they could recover. To keep up with the demand for pelts, trappers moved further inland – all the way to the Rocky Mountains – in what eventually was to become the Westward Expansion, an event that continued for well over 200 years. The awkward and ungainly beaver unwittingly helped to establish a manifest destiny, launching the colorful careers of legendary mountain men like Jim Bridger, Kit Carson and John Fremont in the process.

The beaver’s work habits were the cause of its own undoing. The surest way to catch a beaver is to make a small break in its dam and then hide a steel trap in the breach. When the animal attempts to repair the leak, it gets caught. Although the tactic is illegal today, it was the method used by early trappers to systematically decimate beaver populations. Habitat destruction took a toll as well. Forests were cleared and wetlands were drained for farmland, causing even more beavers to disappear. By the 1840s, only a handful remained in the far reaches of the Adirondacks.

In 1904, New York State released four beavers from Yellowstone National Park in an unsuccessful attempt to boost the Adirondack population.

Several years later, 30 Lake Superior-strain beavers from northern Michigan were introduced there. According to Hilfiker, “As a result, all the beavers in northern New York are descendants of Lake Superior stock.” Southern Tier, and thus Finger Lakes region beavers, descended from animals that migrated out of Pennsyl­vania as a result of that state’s successful restoration program, which began in 1917. Because they are so prolific, the number of colonies increased at an exponential rate until, in 1924, New York opened its first regulated trapping season.

Today, beavers are commonplace. Where there are water, poplars and willows, there probably are beavers – so many in fact that DEC’s DeLong spends an increasing amount of his time investigating nuisance complaints and issuing permits for their removal. Problems can range from plugging highway culverts and flooding farmland to cutting ornamental shrubs – and, yes – the occasional apple tree. In one season, a colony of beavers can easily cut down an acre of trees and flood many acres more. In nature’s world nothing is impossible – just leave it to beavers.


by John Adamski
John is a freelance writer who specializes in wildlife and outdoors subjects, with a particular interest in New York State’s black bears.