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Burlington’s Beavers

By: Remy Crettol and Alicia Daniel

 

Signs of the Beaver, Field Walk

Please join BPRW Field Naturalist Alicia Daniel and WVPD naturalist Remy Cretol for a field walk:  Sign of the Beaver.  July 20th from 5:30 – 8:30 at Ethan Allen Homestead.

 

About Burlington’s Beavers 

August feels early to be laying in wood for the winter, but we have a wild companion in Burlington who is already building up a cache of winter wood–though the wood is to eat, not to burn. All summer long, beavers cut copious amount of hardwood trees and saplings. They use the limbs to shore up dams and lodges and they cache the inner bark and twigs for food under water near their lodge. Beavers are more elaborate in their winter preparations than any other wild Vermont animal. Unlike migrants, who fly south or resident birds and animals who hibernate or forage on sparse winter fare, a beaver over winters with her clan–cozy in the lodge she has built, living on a pond she helped create, and eating food she has stored.

 

In Vermont, if a tree falls in the forest, there’s a good chance that a beaver will hear it.  Not only are beavers abundant and widespread throughout the state, they are also a primary reason that trees do fall.  And not just any trees.  Beavers use their chisel teeth to selectively cut hardwoods that grow in close proximity to water. And in the process, they alter landscapes at a scale second only to humans.

Where are the Beavers?

To see evidence of this process at work you can visit Ethan Allen Homestead.

The Homestead is home to a pair of beavers that make their presence unmistakably known. Trees new and old bear scars from beaver chewing, clearly defined beaver paths bridge bodies of water, and the Homestead hosts multiple dams and two beaver lodges. The beavers are active dusk to dawn during the warmer months of the year preparing for the cold winter to come.

 

Beaver Swimming in a Pond
Photo Courtesy of: Steven David Johnson

More about Burlington’s Beavers

Beavers accomplish their amazing winter survival by creating the conditions that they need to survive. Beavers use water for cover, for transportation, and for refrigeration. They will emerge above the ice to feed (near an escape hole), to repair a dam, and to seek food in case of emergency, but they are not fast runners on land to begin with and are further hampered by snow.  Unfortunately, a beaver on foot in the winter is very vulnerable to predators like coyotes.

 

Beavers need a body of water deep enough that it will not freeze to the bottom.  Using sticks, mud, and even stones, beavers will build dams across flowing rivers and creeks and culverts to create a pond or series of ponds. After a beaver builds a dam and the pond freezes, they may adjust the water level, dropping it by a few inches to create a layer of air under the ice for breathing.

 

This past winter, the water level was so low after a prolonged drought that the resident beavers in the largest wetland at the Homestead were forced to relocate. They moved from the big wetland (which froze solid) to another lodge in a smaller wetland with deeper water.

 

According to Vermont naturalist Bernd Heinrich, beavers build “dams that may stretch a hundred or more yards long, and they impound acres of pond where water levels are raised five or more feet.”  An all- time record dam was constructed in New Hampshire. It was over three quarters of a mile long and the pond it held up had 40 lodges.  Lodges are an adaptation of dam building and are piles of sticks that are later hollowed out and used as homes.  People can even fit in abandoned beaver lodges.

 

Beavers accomplish their engineering feats in groups.  They mate for life and a clan may have an adult pair and several yearlings along with kits that are born during the winter in the lodge.  The young tag along after the parents, learning the skills they need to survive. There is some evidence that beavers learn their food preferences from their clan.

 

Beavers are territorial to others outside their clan. They create scent mounds to keep other beavers away and are known to defend their habitat. This past winter a young beaver was found dead at the Ethan Allen Homestead near the lodge of the resident pair. Its cause of death is unclear. Perhaps it was a kit that did not survive the winter or maybe it was an unwelcome beaver looking for habitat in hostile territory.

 

Beavers are rodents, a group of animals distinguished by their incisors which are covered with enamel in front, but not behind, so that as these animals chew, they wear away the back side, sharpening their teeth like chisels. Beavers turn their heads sideways to bite into standing trees and you can see their teeth marks meeting together on a stump.  Beavers close relatives include squirrels, mice, porcupines, and muskrats.

 

The ponds beavers create are habitat for many plants and animals.  The red eft, a small slow moving and bright orange amphibian commonly seen in Charlotte woods in the fall is the immature stage of the Red Spotted Newt.  And though the same species is distributed throughout the Southeastern U.S., the terrestrial stage only exists in the Northeast.  One hypothesis explaining this pattern is that the Red Spotted Newt is dependent on the beavers to create ponds for breeding habitat in its northern range and the “life span” of a beaver pond is generally only 15 to 20 years.  Northern Red Spotted Newts have an eft stage so that they can disperse from the pond to find other habitat, like a new beaver pond.

 

After a pond is abandoned and drains, a beaver meadow is what remains.  As silt accumulates behind a beaver dam, a flat plain is created.  When the beavers run out of food or die and the pond is abandoned and drains, this new soil regenerates into a wet meadow–great habitat for animals like moose.  Another common pattern that results from beaver activity in a forest is a signature ring of softwoods that persists even after the beavers have moved on.  By cutting only hardwoods, beavers create a circle of uncut spruce, pine, fir and hemlocks that surround the higher elevation ponds, while lower elevation ponds have white pine and hemlocks around them.  If you look closely you may see the beaver chewed stumps of aspen, birch and maples under this canopy of softwoods.

 

When explores and colonists arrived in North America, beaver populations were estimated to be between sixty and two hundred million.  So, it may come as a surprise that you would have been hard pressed to find even one beaver at the turn of the last century anywhere in Vermont.  Hunted to near extinction for their pelts (which were popular in Europe for hats), beavers were only reintroduced into Vermont in 1921.

 

If you decide to go looking for beavers here are some signs. You have a good chance of seeing one this time of year, especially at dusk.  The characteristic sharpened like a pencil look gives beaver sticks an unmistakable appearance.

 

 

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