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Beavers

Signs Of An Active Beaver Pond

4-7-14  floating beaver logs IMG_0159Beaver ponds have finally started to melt, making it easy to determine whether or not there have been beavers living in any existing lodges over the winter. The tell-tale sign is floating de-barked sticks and branches. During the winter, beavers leave their lodge and swim out to their underwater food supply pile and haul branches back into the lodge where they chew them into foot-long pieces for easy handling. The bark is removed and eaten as the beaver holds the stick and turns it, much as we consume corn on the cob. When little or no bark remains, the stick is discarded out in the open water. These sticks remain hidden underneath the ice on the surface of the water until warm weather arrives and the ice begins to melt. At this point the sticks and branches become visible, and often extend several feet out from the lodge. These sticks will not go to waste, but will be used for dam and lodge repairs. (Photo taken standing on lodge.)

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Many Beavers Still Locked Under Ice

3-20-14 beaver on ice IMG_3980Although there have been sightings of beavers this spring, precious few beaver ponds have openings or ice thin enough for beavers to break through in order to procure fresh food. This photograph was taken one year ago, and one can only hope, for the beavers’ sake as well as our own, that temperatures rise soon. The winter supply of food beavers store under the ice in the fall may well be as low as many people’s wood piles are this spring, in which case, many beavers’ lives depend on the ice thinning soon.

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A New Book for Budding Naturalists

COVER-BeaversBusyIs there a youngster in your life who might love his or her own book about beavers? My third children’s nature book, The Beavers’ Busy Year, has just been released. Having been an ardent admirer of this rodent for many, many years, it is gratifying to have had a chance to instill a love for beavers in youngsters age 3-8 with this non-fiction book. The adaptations of beavers’ noses, eyes, ears, fur, feet and tails are highlighted in the text and photographs take the reader through the seasons of the year from a beaver’s perspective. Activities at the end of the book engage children in matching photographs of various beaver signs such as tracks, scent mounds and incisor marks with written descriptions. There are also activity/informational sections on beaver tails, beavers as engineers and creators of habitat for other wildlife, and dam building. It should be available at your local bookstore, but if not, I’d greatly appreciate your letting them know about it. Thank you!


Porcupine Feeding Technique

12-18-13  porcupine incisor marks IMG_0150In the winter, the bulk of a porcupine’s diet is the inner bark, or cambium, of trees. The porcupine removes the outer bark (unless the tree is young or has thin outer bark and then it eats the outer bark as well) in order to reach the cambium layer, which lies directly beneath the outer bark. At this point the exposed surface is very smooth, more finely finished than the work of a beaver. Then the porcupine removes the cambium in small, triangular patches, each patch composed of five or six scrapes converging at one point, like sticks in a tepee. The point where the scrapes meet is where the upper incisors are placed and held fixed against the tree. The lower incisors scrape, making a fresh path with each scrape, as the lower jaw swivels in a narrow arc.

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Beaver Breath

12-2-13 beaver breath  074It’s very subtle, but in winter, especially when it is very cold outside, there is a way to tell if a beaver lodge is occupied. The temperature inside the lodge remains relatively stable at around 34 degrees Fahrenheit. When snow falls, it provides added insulation, raising the interior temperature of the lodge slightly. A layer of fat and thick fur keep beavers warmer than the air inside the lodge, plus they raise their body temperature even more by sleeping piled on top of one another. All the moist, warm air that beavers give off through breathing and evaporation escapes through the (mudless) vent that goes up through the center of the roof of the lodge to its apex. The vent’s purpose is the exchange of air; when the warm air inside the lodge rises and hits the cold air outside the lodge, it condenses and forms water vapor that is visible, indicating that there is life inside.

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Beavers’ Last Hoorah

11-22-13  beaver dripping 107We’re right on the edge 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 drops to 16 degrees F., they no longer try to break through the ice and are sealed under it until spring, unless there’s a mid-winter thaw. Once they are confined by the ice, their activities outside the lodge are minimal. Beavers leave their lodge in winter primarily for two reasons: to swim out to their winter food supply pile and retrieve a stick which they bring back into the lodge to eat, and to defecate. Other than those excursions, they spend most of their day in the dark, enduring a lodge temperature of about 34 degrees F. (Thanks to Kay Shumway for photo op.)

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Beavers Gathering & Storing Winter Food Supply

10-15-13  beaver winter food supply pile 292(Part 3 of 3 Beaver posts)
In the fall, beavers spend weeks cutting, transporting and piling sticks and branches whose bark, twigs and leaves will hopefully provide them with sustenance through the winter. With no access to land once ice forms, beavers rely on the food that they have had the foresight to store on the bottom of the pond in the fall, as close to the main entrance to their lodge as possible. Initially the beavers dive down and stick the butt end of the branches into the mud. Once anchored, these branches form the base of a growing pile which often sticks out above the surface of the pond. (The portion of the pile above the water is not accessible to the beavers once the pond freezes.) According to beaver biologist Leonard Lee Rue, a beaver colony needs to store between 1,500 and 2,500 pounds of edible bark, twigs and leaves (this weight doesn’t include the wood, as they don’t eat wood) if it is to sustain them through the winter. As one would suspect, southern beavers do not need nor make winter food supply piles.

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Beavers Reinforcing Dams

10-15-13 beaver dam 208(Part 2 of 3 Beaver posts)
Beavers repair and strengthen their pond’s dam much as they do their lodge in the fall. New sticks are added and mud is retrieved from the pond bottom just below the dam, making the water deeper there than in the rest of the pond. Beavers dive down, dig up a load of mud and carry it beneath their chin and front feet to the dam. They then use their front feet to push the mud on top of and in between the pieces of brush on the dam (see front foot prints in mud, insert A). Because beavers spend so much time reinforcing their dam, it is not unusual to find their 1 1/2 –inch long, fibrous scat (insert B) in the water right below the dam (they keep their lodge relatively clean by defecating only in water).

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Beavers Refurbishing Lodge

10-14-13 refurbished beaver lodge 248This is the time of year when the industriousness of beavers can determine whether or not they survive through the winter. There are three major tasks for a beaver colony to tend to in the fall: refurbishing their lodge; strengthening and repairing their dam; and cutting and storing their winter food supply. They tend to perform these tasks in this sequence, tackling the lodge first. If the water level is high, the beavers will raise the floor of the lodge and the roof of the sleeping chamber. Every fall they add new material to the exterior of the lodge to strengthen the entire structure – typically sticks intertwined that create walls two feet thick or more. At this point the beavers coat the lodge with mud that they dredge up from around the base of the lodge (which greatly increases the depth of the water near the lodge). The apex of the lodge is not coated, allowing fresh air to filter down into the sleeping chamber. Once cold weather arrives, the mud hardens to the consistency of concrete, making the lodge is impenetrable to predators that can approach the lodge once the pond freezes. (In photo, note the fresh eastern hemlock branches and mud that have recently been added to the lodge.)

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Beaver Tail Boosts Balance

beaver tail 062A beaver’s tail is a wondrous thing. Beavers steer and propel themselves with it, store fat for the winter in it, regulate their body temperature with it, use it as a prop when sitting or standing and signal alarm with it by slapping it against the water. While these functions are fairly well known, there is another use that is not observed as often. When floating on top of the water, beavers use their tail as a stabilizer, to keep their body upright. As this photograph illustrates, beavers often raise their tail out of the water in order to stabilize themselves.

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Mutual Grooming

8-1-13 beavers grooming each other IMG_2714Beavers spend a great deal of time tending to their coats, grooming several hours a day throughout the year. Grooming consists of removing sticks and debris that have become embedded in their fur, as well as applying oil from their anal glands to waterproof their fur. Waterproofing is essential, as it prevents the cold water from penetrating their fur. Typically they sit with their tail between their hind legs, stretched out in front of them, with their anal glands exposed. Beavers procure the oil with their front feet, and use all four feet to comb it through their fur. The two inside nails on both of their hind feet are split, increasing the efficiency with which they can apply the oil. Sometimes two beavers will groom each other, engaging in “mutual grooming.” The male and his offspring begin to groom each other when the kits are only two weeks old, yearlings and kits from three weeks on, and the mother and kits when the young are four weeks old. Mutual grooming continues as long as they are a family unit. ( I am humbled by the response to yesterday’s post. You will each be hearing from me soon. )


Beaver Ponds & Waterfowl

6-5-13 mallard & ducklings 151The relationship between beavers and waterfowl is a strong one. In creating ponds and wetlands, beavers provide valuable waterfowl habitat. Beaver ponds are attractive to most dabbling duck species, particularly American Black Ducks and Mallards (pictured). Dead snags that are often found in beaver ponds provide Hooded Mergansers, Common Goldeneyes, Buffleheads and Wood Ducks with nesting cavities. During spring and fall, beaver ponds are used by migrating waterfowl, such as Green-winged Teal and Ring-necked Ducks, for the fuel they provide (aquatic invertebrates, plant seeds, tubers, buds and rhizomes). Waterfowl surveys in 2002 in Wyoming found that rivers and ponds with beavers had 75 times more ducks than those without beavers.


Beaver Scent Mounds

4-30-13 beaver scent moundsThis is the time of year when two-year-old beavers leave their lodges and strike out on their own, primarily because the woods surrounding a pond usually can’t support more than one family of beavers. Beavers are exceptionally territorial; once they’ve established a lodge, they do not take kindly to interlopers. In order to make this perfectly clear to house-hunting young beavers, in the spring resident beavers build what are called scent mounds — piles (up to three feet in height, but usually much smaller) of mud, leaves and pond-bottom debris — around the perimeter of their territory. They then smear castoreum, a substance that comes from their castor sacs, over the mound. Chemicals in the castoreum convey to roaming young beavers that this particular pond is spoken for.


Coyotes and Beavers

3-12-13 coyote & beaver lodge2 IMG_6223A study of coyote prey (through stomach contents) in the Adirondack Mountains of New York revealed that beavers were second only to white-tailed deer. This photograph shows that, possibly for the last time this winter, a coyote recently took advantage of a still-frozen-but-fast-thawing pond by walking across it in an attempt to reach an active beaver lodge. Once there the coyote attempted to dig into it in order to reach the inhabitants. A hard, two-to three-foot-thick wall of frozen mud, logs and sticks kept the beavers well protected, as it was designed to.


Beaver & Otter Cohabitation

2-22-13 otter scat and beaver track2 IMG_3211It is not coincidental that you often find otters residing in beaver ponds. There appears to be a commensal (one animal benefits while the other is unaffected) relationship between these two animals. The beaver is unaffected – it is a herbivore, so its food supply is not threatened by the presence of otters. (While an occasional beaver is eaten by an otter, it is a rare occurrence.) The otter, on the other hand, benefits from abandoned as well as active den sites (both beaver bank dens and lodges) as well as an ample supply of fish due to the impoundment of streams by beavers. While I was aware that otters often take over abandoned beaver lodges, I only recently learned that the lodge does not have to be uninhabited for otters to move in. This was confirmed when I discovered a large amount of otter scat (mostly fish scales and crayfish shells) on top of a beaver lodge, right next to the hind foot print of a beaver. Freshly placed sticks on the lodge (it is in open water) indicated that it was occupied by beavers, while an otter’s stream of air bubbles could be seen as it exited the lodge and popped its head up above the surface of the water.


Signs of Active Beavers

beaver tracks in snow IMG_3255If beavers have bank dens on rivers that remain open all winter, they are not subjected to the confines of a dark, damp lodge for several months. They have access to fresh food year round, and aren’t limited to the pile of aging branches under the ice that they stored last fall near their lodge. On the other hand, beavers that do live in ponds that freeze over often can find an opening in the ice if there’s a big enough January or February thaw. In either case, signs of their activity on land can be found.


A Great Christmas Present!

If you’re looking for a present for someone that will be used year round, year after year, Naturally Curious may just fit the bill.  A relative, a friend, your child’s school teacher – it’s the gift that keeps on giving to both young and old!

One reader wrote, “This is a unique book as far as I know. I have several naturalists’ books covering Vermont and the Northeast, and have seen nothing of this breadth, covered to this depth. So much interesting information about birds, amphibians, mammals, insects, plants. This would be useful to those in the mid-Atlantic, New York, and even wider geographic regions. The author gives a month-by-month look at what’s going on in the natural world, and so much of the information would simply be moved forward or back a month in other regions, but would still be relevant because of the wide overlap of species. Very readable. Couldn’t put it down. I consider myself pretty knowledgeable about the natural world, but there was much that was new to me in this book. I would have loved to have this to use as a text when I was teaching. Suitable for a wide range of ages.”

In a recent email to me a parent wrote, “Naturally Curious is our five year old’s unqualified f-a-v-o-r-I-t-e  book. He spends hours regularly returning to it to study it’s vivid pictures and have us read to him about all the different creatures. It is a ‘must have’ for any family with children living in New England…or for anyone that simply shares a love of the outdoors.”

I am a firm believer in fostering a love of nature in young children – the younger the better — but I admit that when I wrote Naturally Curious, I was writing it with adults in mind. It delights me no end to know that children don’t even need a grown-up middleman to enjoy it!


Beavers Ice-Bumping

Ice is starting to form on ponds, and days are numbered when beavers can be out grooming themselves on land or eating freshly-cut branches.  As long as the ice is thin enough to crack by swimming up under it and bumping their heads against it, they will do so, for soon it will be thick enough to lock them into their pond. Life under the ice is challenging.  At 32 degrees F. a beaver’s resistance to heat loss in water is about 1/8th of that in air at the same temperature. This is due to the fact that its fur is compressed in the water, allowing the insulating air between the hairs to escape — a beaver’s pelt accounts for about 24% of its total insulation in water and body fat is responsible for the rest.  Heat is also retained through a beaver’s tail and hind legs, which serve as heat exchangers.  In the summer, a beaver can lose 25% of its body heat through its tail, but it only loses 2% in winter. Even so, it’s no wonder beavers risk getting a headache in order to see the sun for the last time until spring.


Red Squirrel Sign

If you find a mushroom hanging in an unlikely spot, such as from tree branches or tucked into the bark of a tree where it didn’t grow, it’s likely that you have happened upon the work of a red squirrel (Tamiasciurus hudsonicus).  Red squirrels are known for their habit of snipping mushrooms and hanging them from branches and rough bark in order to dry them before collecting them and caching them for dining on later in the winter.   Unlike beavers, which share their stored cache of winter food with family members, red squirrels keep their cached fungi all to themselves.


Beavers Gathering Winter Food Supply

Shorter days and longer nights trigger a flurry of activity for beavers.  There is a lodge to be built, rebuilt, enlarged or repaired and a dam to be built, repaired or reinforced.  As, or more, important than these tasks is cutting, gathering and transporting a supply of food for winter. Once the pond is frozen, the only food available to beavers is that which they have stockpiled under the ice.   Thus, beavers spend many an autumn night adding to a growing pile of submerged branches close to the lodge.  More thought is put into the harvesting of a winter food supply than one might imagine.  Before cutting down a tree a beaver often tests its readiness by biting into the bark.  If it is not in just the right condition — for instance, if there is still too much sap in the tree — they may speed up the drying of the bark by girdling it, and returning in several days to cut it down.  If limbs and branches are stored underwater before the bark is ready, they will ferment and sour, making them unfit for food.


Grooming Beaver

Beavers are constantly grooming and oiling their fur to waterproof it. Typically when grooming, a beaver sits upright with its tail curled under its body and extended in front of it between its two hind legs. This allows the cloaca (an opening which contains ducts for everything from evacuation to reproduction, plus oil and castoreum glands) to be exposed. The beaver uses its front feet to retrieve creamy-yellow waterproofing oil from its inverted oil glands and then rubs it carefully over all of its body. Without constant waterproofing the beaver’s fur would soon become soaking wet and the beaver would not be able to tolerate the cold water.


Naturally Curious Interview – Part 2

Chris Mazzarella, on his blog “Forest Forward” has posted the second half of his interview with me.  To read it, you can go to http://forestforward.com/2012/05/07/an-interview-with-mary-holland-part-two/


Beaver Scat

 

Beavers are meticulous housekeepers, in that they almost always defecate in the water, not in their lodge, and rarely on land. The best place to find their scat, should you be so inclined, is where they have been working for an extended period of time — for example, in the water adjacent to their dam.  Their scat consists of kumquat-size pellets, which, as you might expect, are full of tiny bits of woody fiber.  The pellets are essentially little balls of sawdust, and disintegrate easily if disturbed. Their light color makes them visible even under water.  Congratulations to all who guessed correctly — I’ll make the next mystery post even more challenging!

 


Beavers See the Light of Day

Although some ponds have had open water in spots all winter, many have remained frozen over until the recent warm weather started to melt the ice. The first open water often appears close to the lodge and along the dam of a beaver pond. It doesn’t take long for resident beavers to detect an opening, for it’s a ticket to fresh food!  The first plant that beavers head for, if it’s growing in the area, is skunk cabbage.  Being the first wildflower to push up through the snow, it’s usually available when ponds first open up.  Aspen, willow and alder leaves, grasses, the rhizomes, leaves and flowers of water lilies, sedges, ferns, fungi, berries, mushrooms, duckweed and algae are eaten in the spring and summer by these large rodents we think of as strictly bark eaters.  Photograph by Kay Shumway.

 


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