The beaver is North America’s largest rodent and New York State’s official mammal, and it is a familiar resident in much of the Finger Lakes Region. Once bordering on extinction, the beaver population has made a significant comeback – enough so that it has at times become something of a nuisance.
The beaver story dates back to the 1600s in Europe, when beaver pelts were used to make the finest in gentlemen’s fur felt hats. Colonial explorers found beavers to be so plentiful that the animals were being depleted faster than they could recover. But indiscriminate trapping wasn’t the only reason for the beaver population decline. Habitat destruction took a toll as well. Forests were cleared and wetlands were drained for farmland, causing even more beavers to disappear. By the 1840’s, only a handful of beavers remained in the northern reaches of the state. But in the early 1900s, New York began a beaver restoration program by introducing a strain of beavers from northern Michigan.
Southern Tier, and thus Finger Lakes Region beavers, are descended from animals that migrated from 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 New York opened its first regulated beaver trapping season in 1924.
Beavers are vegetarians and eat plants of every kind. In winter they survive on a diet of tree bark, which is about the only food available. Summer diets include 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 to build their lodges and dams. When they have exhausted their food supply – something that may take years – beavers abandon their territory and move on.
By damming a stream, beavers raise the water level surrounding their lodge enough to create a pond that submerges the entrance, ensuring 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 while leaving 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 longer and much higher. Beavers start by pushing sharpened sticks into the mud bottom of any stream that satisfies them. Considerations include an ample supply of alder, poplar, or willow, and perhaps all three. Sticks are jammed together and packed with small 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.
Today, beaver occurrences are almost commonplace – so much so that state wildlife managers spend an increasing amount of time investigating nuisance complaints and issuing permits for their removal. Problems can range from plugging highway culverts and flooding farmland to cutting down ornamental shrubs. 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.