An online resource based on the award-winning nature guide

Beavers

Beavers Eating & Grooming

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This photograph conveys the essence of a beaver’s summer – eating and grooming… more eating, more grooming. During the summer months, beavers feed on non-woody vegetation (grasses, ferns, aquatic plants, etc.) 90% or more of the time. (During March/April and October/November, their diet switches to 60%-90% tree bark, and during the winter, bark from trees stored under water composes 100% of their diet.)

When beavers are not eating, much of their time during the warmer months is spent grooming, both themselves as well as each other.  Combing debris out of their coat (with the help of a split nail on both hind feet) and applying oily material from their anal glands to waterproof their fur consume much of their waking hours, both at night as well as at both ends of the day. (Castoreum, produced in castor sacs, differs from anal gland secretion, and is used primarily to mark territory.) (Thanks to Roger and Eleanor Shepard, and Sara and Warren Demont for photo op.)

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Beavers Up and Out

4-16-18 beaver l 690Although most of the Northeast is snow-free, parts of northern New England still have a while to go before bare ground is visible. Most beaver ponds, however, are open and the beavers have been taking advantage of their ability to access fresh food after a long winter of water-logged woody plants. While this particular beaver is dining on bark, most beavers head for any green plants, buds, grasses, etc. that are poking their heads above the ground. A particular beaver delicacy this time of year are the leaves and blossoms of skunk cabbage.

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Beavers Breaking Ice

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We’re right on the verge of when beavers will no longer be able to smell fresh air, see the sun and obtain fresh bark. Until the temperature drops to around 16 degrees F. they continue to break through the thin ice covering their pond. Once the temperature remains in the teens or lower for several days, they no longer try to break through the ice and are sealed under it until spring, unless there’s a mid-winter thaw.

Once beavers are confined by the ice, their activities outside the lodge are minimal. Beavers leave their lodge in winter primarily for three reasons: 1) to swim out to their winter food supply pile and retrieve a branch which they bring back into the lodge to eat, 2) to defecate in the water, and 3) to mate in January or February. Other than these excursions, they spend most of their days in the dark, enduring life in a lodge that has a temperature of about 34 degrees F. (Thanks to Kay and Peter Shumway for photo op.)


Otter Brown-Out

9-28-17 otter brown-out 049A5342North American River Otters are not territorial in the classic sense of marking territorial boundaries. Instead they mark prime resource areas within their territory. Often, the site is near their den or a productive food area. They visit these sites repeatedly to urinate, defecate and roll around on the ground – so much so that the surrounding vegetation is often dead or dying and is referred to as a “brown-out.”

If an otter has been eating fish, its scat is often just a pile of fish scales. However, if it has been dining on crayfish and it is fresh, the scat can be tubular. No matter what form otter scat takes, a tell-tale sign (in addition to fish scales and/or crayfish exoskeletons) is the presence of clear, white or yellow mucus (scat-jellies). It is not always deposited, but occasionally you do find it. The origin of this mucus is not known – most likely it’s from the otter’s intestinal tract or its anal glands. Research shows that the presence of mucous deposits in some otter species indicates reduced prey availability or reproductive state.  (Photo: Tubular otter scat is circled in red. Mucus is on right side of photo. Thanks to David Putnam and Natalie Starr for yesterday’s and today’s photo op.)

Reasons why Mystery Photo was not

       Black Bear: Scat consists primarily of crayfish remains.

Beaver: Beavers defecate only in water, and individual pellets consist of tiny woody fragments resembling sawdust.

       Raccoon: Raccoons have latrines where multiple scat is deposited, similar to otters. However, only otters deposit mucus.


Beavers Preparing For Winter

9-12-17 beaver2 20160905_5707The lazy, hazy days of summer are dwindling, and beavers’ internal clocks are telling them it’s time to batten down the hatches and prepare for several months of life below the ice. This entails adding a significant amount of mud to the outside of their lodge. The mud freezes and creates an impenetrable barrier between them and predators such as coyotes that, thanks to ponds being frozen, will have access to beaver lodges. This mud is anchored by the addition of debarked branches and logs that have provided the beavers with meals of cambium during the summer.

A beaver can transport its own weight in material (roughly 45-60 pounds). Retrieving debarked pieces of wood in many cases involves carrying them over both land and water, using only jaws and sometimes a shoulder for support.  A beaver’s short, muscular neck and its powerful lower jaw muscles make this possible. Try lifting one of the larger logs on a lodge or beaver dam sometime. Then imagine carrying it any distance in your mouth with no assistance from your hands. (This feat rivals that of a moose carrying two 25 – 30 pound antlers around for several months.) While there are recorded cases of beavers felling trees 150 feet tall and 5 feet in diameter, logs of this size are not used as building material for dams and lodges, but rather the bark and upper branches provide them with food.  (Thanks to Roger and Eleanor Shepard and Sara and Warren Demont for photo op.)


Beavers Mating

2-17-17-beaver-img_3766Under ice-covered ponds and lakes in dark, cold water, sometime between December and March, beavers mate. Latitude and climate affects the length of the breeding season, which is shorter and later in colder, more northern locations and longer and earlier in warmer, more southerly regions. February is the peak mating season for New England beavers.

Beavers are classified as monogamous, as once a bond has formed, they remain as a pair throughout their life until one of the pair dies, at which point a new mate is found. However, this does not mean they don’t stray. In a study of beaver colony genetics, researchers discovered that more than half of the litters had been sired by two or more males. So much for monogamy.

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A Beaver’s Winter Quarters

2-1-17-beaver-lodge-interior-img_4899What exactly is it like inside an active beaver lodge in winter? It’s dark, damp and around 32°F. The living chamber inside usually has a ceiling no more than two feet high with a diameter of 4 to 6 feet, depending on the number of individuals in the family. (A typical beaver family is composed of an adult male and female, 2 to 3 yearlings, and 2- 4 kits that were born in the spring.) Fresh air enters and carbon dioxide leaves through a central vent (where mud is not applied) and through small holes that remain under logs on the side of the lodge. When there isn’t much snow and the outside air falls well below zero, the temperature inside may drop to a degree or two below freezing, but if the sun is out, it warms right back up again during the day.

The dampness is due to the beavers’ repeated need to enter the water both to retrieve sticks from their nearby food supply pile and to defecate. Upon returning to the lodge, the humidity inside increases due to the water draining from the beavers’ fur. No small wonder that if a January thaw permits, beavers will exit their pond for some fresh air, food and a little bit of sunshine.

Naturally Curious is supported by donations. If you choose to contribute, you may go to http://www.naturallycuriouswithmaryholland.wordpress.com   and click on the yellow “donate” button.