An online resource based on the award-winning nature guide

Beavers

Beaver Kits Out & About

9-20-16-beaver-kit-20160919_0902Last January or February beavers mated (in the water) and in May or June gave birth to 1 – 9 (average 2 – 4) precocial kits. Young beavers are born fully furred, their eyes are open and their incisors are visible. Within four days they are able to swim, but it’s usually a month or more before they are seen outside the lodge. Part of the reason for this is their buoyancy, which prevents them from diving down through the tunnel to get out of the lodge. By the age of two months they are able to submerge themselves and they have begun grooming the water-repelling secretions of their anal glands onto their fur, so they are fully water-repellent. They are ready for their semi-aquatic life.  Sometime between two and three months is when they are often first observed by humans — usually in late August or September you can see three generations of beavers in an active pond.

When they are three days old, kits begin to eat vegetation brought to them inside the lodge by their parents and year-old siblings. By the time they are two months old, they are weaned. The three-month-old kit pictured (measuring about a foot from head to base of tail) is able to debark a twig as deftly as its parents.

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Beavers Consuming Herbaceous Plants

8-31-16 beaver cutting fern 052

One associates Beavers with a fairly strict diet of bark and twigs. While their winter diet consists primarily of woody plants, they consume a variety of herbaceous and aquatic plants (as well as woody) during the spring, summer and fall months. Shrubs and trees make up roughly half the spring and autumn requirements, but as little as 10% of the summer diet when herbaceous plants such as sedges and aquatic plants become available.

Recent observation of a local active Beaver pond revealed that Interrupted Fern (Osmunda claytoniana), Jewelweed/Touch-Me-Not (Impatiens capensis) and grasses are high on the list of preferred foods of one Beaver family during the summer, although woody plants such as poplars (Populus spp.) and Paper Birch (Betula papyrifera) have also been consumed in fairly large quantities.   All too soon Beavers in the Northeast will be limited to the bark of branches they’ve stored under the ice. Until this time, they take advantage of the accessibility of more easily digested herbaceous plants. (Thanks to the Shepards and Demonts for photo op.)

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All In A Day’s Post

beaver hauling food to lodge 245Every day I head out with the hope of finding something interesting enough to write about and share on my blog, and which I can also manage to photograph.  There are days when it happens within minutes, but typically it consumes the better part of half a day. I thought I would take this opportunity to try and convey the sensory experience of this endeavor by describing yesterday’s outing.

I arrive at the beaver pond late in the afternoon, hoping for a glimpse of the two beaver kits that have been seen here in recent days.  Hidden behind ferns and shaded by young white pines, I set up my tripod and camera and settle down, hoping my arrival has not been observed.  I am accompanied by Emma, my lab, who for 12 years has patiently sat by my side motionless as we waited for the expected and unexpected to present itself. The sun is close to disappearing behind the trees, but lingering light provides a warm glow to the pond.

Silence greets me, but not for long. There is no sign of beavers, but I am serenaded by a lone Hermit Thrush, bidding a sweet goodnight to the surrounding woods and all who reside therein.  Soon after the Hermit Thrush’s flute-like song ceases, a chorus of plunking Green Frogs starts up.  Still no beavers, but I hear a splash from a corner of the pond that is hidden from view, and out flies a Broad-winged Hawk, whose empty talons tell the tale of a failed attempt to catch a frog or other aquatic resident.  I suddenly hear the high-pitched whining of young beavers coming from within the lodge that is roughly 150 feet directly across the pond from where I sit. This often occurs when a parent leaves the lodge, so I am on high alert.  Cedar Waxwings appear, perching on snags and flying out over the pond to snatch insects from a recent hatch before returning to their perch.

The sun is all but gone as a lone adult beaver surfaces and heads to the far end of the pond.  As silently as possible I walk along the side of the pond until I hear the familiar sound of rodent incisors gnawing rapidly on wood.  There, at the shoreline, the beaver is cutting a branch off a limb of a sloping tree that is within its reach.  Soon the chewing stops and the beaver grasps the cut branch in its mouth and swims the length of the pond to the lodge where its young eagerly await a freshly-cut meal.  When it gets to within several feet of the lodge, the beaver silently disappears beneath the water and moments later is greeted with the exuberant, anticipatory whining of its offspring.  With luck, I may have captured more than one post’s photograph, but even if I haven’t, my ears and eyes (and soul) have reaped enormous benefit from the effort.

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Beavers Seeking Herbaceous Plants

3-16-16 beavers out IMG_1252A recent light snow provided an opportunity to confirm that northern New England beavers have gained access to land and are seeing the sun for the first time in several months. They, along with any beavers living north of the 39th parallel, may well reap some benefit from the change in our climate. Further south, there is no real winter and beavers do not have to cope with a limited amount of stored food for there is usually no ice on ponds. Milder winters and early springs mean more time for Northeastern beavers to access herbaceous food and fresh bark, and less time locked under the ice.

Unbeknownst to many, a large portion of a beaver’s spring, summer, and fall diet consists of herbaceous food – grasses, sedges, ferns, fungi, berries, mushrooms, duckweed and even algae. When beavers first leave their ponds in the spring, one of the first foods they head for is skunk cabbage, as it is one of the earliest flowering plants to emerge (often when snow is still on the ground). Beavers also relish the new foliage of aspen, willow and alders. When they are accessible, the rhizomes, leaves and flowers of both yellow and white pond lilies are favorite foods. Come late fall, when lush greenery has disappeared, beavers up their intake of bark (cambium) and store a pile of branches on the bottom of the pond   close to their lodge, where they have underwater access to it all winter.

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Beavers To The Rescue

12-23-15 beaver dam & pussy willow IMG_5739With peepers peeping and pussy willows starting to poke their heads out of local willows in mid- late December, it is clear that in the coming years humans will need to adapt to the effects of climate change. Help with that mission may come from many sources, including beavers, whose landscape alterations have been shown to mitigate many of the more extreme conditions caused by climate change. Where beaver dams are persistent, they may sequester sediment and create wet meadows that can moderate floods, augment early summer baseflows, sequester carbon in soils and standing biomass, decrease ecological problems posed by earlier spring stream recession, and potentially help cool early summer and post-wildfire stream temperatures. (Jeff Baldwin, California Fish & Game) How fortunate that silk hats became fashionable in the early 1800’s, decreasing the demand for beaver pelts and rescuing beavers from extinction.


Rodent Incisors

12-3 woodchuck skull IMG_7187Rodents have two pairs of incisors that oppose each other; two in the front of the upper jaw and two in the front of the lower jaw. These four teeth never stop growing, and thus have to be constantly filed down. (Squirrel incisors grow about one-half inch a month.) While nipping herbaceous plants and cutting into bark help do this, it isn’t enough to significantly wear down the teeth. When mice, beavers, woodchucks and other rodents nip or gnaw food, they move their jaws in such a way that these two pairs of teeth grind against each other. Most rodents have hard orange enamel on the outer side of their incisors (woodchucks are our only rodent with white enamel), and softer dentine in the back. When the incisors grind against each other, the dentine wears away faster than the enamel, creating a sharp, chisel-shaped edge to the incisors. This, more than anything else, keeps the growth of rodent incisors under control, just as a nail file keeps our nails from getting too long.

If a rodent breaks an incisor, there is nothing to wear down the opposing incisor. The tooth opposite the missing incisor will continue to grow unchecked in a circle until it causes the death of the rodent, either by piercing its skull or by preventing the animal from being able to eat. In the pictured woodchuck skull, the lower left incisor has broken off, allowing the upper left incisor to grow through the woodchuck’s palate and into its brain.

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Beaver Incisors

10-29-15 beaver incisor marks 025Yesterday’s design was made by a beaver as it removed bark from a tree. The light-colored, curved little “bumps” that run horizontally across the middle of the tree were made by the two incisors in the beaver’s upper jaw. When eating the sought-after cambium layer of a tree, beavers grip the tree with their two upper incisors as they scrape towards their upper jaw with their two bottom incisors, sometimes creating this pattern. (Individual marks where the upper incisors gripped the bark and the four incisors didn’t quite meet can be seen in the insert.)

The ever-growing incisors of rodents are harder on the front surface (outer layer is hard enamel, colored orange from iron in a beaver’s diet) than the back (softer dentine), so the back of each incisor wears away faster than the front, creating a sharp, chisel-like edge to these four specialized teeth. So functional are beavers incisors as cutting instruments, Native Americans used to insert a beaver incisor in a wooden handle and use it to cut bones and to shape their horn-tipped spears.

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