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Beavers

Unusual Beaver Activity

Beavers are known for their ever-growing incisors which allow them to cut trees down, eat the cambium (a nutritious layer just beneath the bark) and cut what’s left into pieces they are able to haul and use as building material for dams and lodges. More often than not, it’s straight forward work.

Occasionally not every step is taken – you can find standing trees that had the bottom three or four feet (as high as the Beaver could reach) of cambium removed without the trees being felled.  You can find de-barked logs that have been left where they fell and not carried or floated to the dam or lodge as construction material.  It’s also not unusual to find standing trees where several times a Beaver has attempted but failed to cut all the way through.

Recently John Twomey brought to my attention a tree felled by Beavers unlike any other I’ve ever seen:  one or more Beavers had cut down a Paper Birch and eaten the cambium layer, leaving the tree clean of bark.  At some point they cut into the tree every 18 inches or so, not quite severing the pieces, but leaving them connected by a core of wood that ran the length of the tree. If any readers have seen anything similar to this, or if you have an idea as to why Beavers would have cut the tree in this fashion, Naturally Curious would love to hear from you.  (Photo by Prentice Grassi of his sons investigating said tree earlier this spring.)

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Beavers Foraging

Even in the coldest of winters, there is often a thaw around this time of year that frequently allows beavers to escape the cold (+/- 34°F) dark lodge where they reside during most of the winter.  Our most recent thaw was such that in many beaver ponds, ice didn’t even have to be broken in order for resident beavers to forage for food on land.

When beavers are confined to complete darkness (under the ice) their 24-hour circadian cycle extends to a 28 hour day. During this time beavers sleep for longer periods at a time and thus need less food.  As spring approaches and the days lengthen, the slightest exposure to daylight will reset the beaver’s biological clock back to the circadian cycle. (Leonard Lee Rue, Beavers)  (Photo by Alice Trageser)

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Beavers Feeding Young

In summer Beavers spend considerable time on land searching for, cutting and bringing vegetation back to their young in the lodge.  Their woody plant preference (they eat large amounts of herbaceous plants during the warmer months, but also some trees) tends towards the inner bark (cambium) of willow, aspen, maple, birch, cottonwood, beech, poplar, and alder trees. This beaver, however, has retrieved a Red Oak sapling for its offspring.

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Muskrats & Spatterdock

6-12-19 muskrat eating water lily flower bud1B0A0488Cattails, sedges, rushes, water lilies and grasses make up the bulk of a Muskrat’s diet although these aquatic rodents have been known to occasionally dine on fish, crustaceans and freshwater clams.

Muskrats typically don’t eat their food where they find it – they usually bring it out to a feeding platform in the water, which provides them with some protection from predators. However, they make an exception for Bullhead Pond-lily flower buds (Nuphar variegata), also known as Spatterdock, which they often devour on the spot wherever they find them (see photo). Beavers, Porcupines (yes, Porcupines can swim), White-tailed Deer and waterfowl also dine on the leaves, rhizomes, buds, flowers and seeds of Bullhead Pond-lilies.

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What Goes On When We’re Not Looking

5-17-19 beaver and ducks_U1A0432A blind is a wondrous thing, allowing you to observe natural behavior in a natural setting. Having watched beavers for over 50 years, I thought I had seen most of what there is to see regarding Beaver behavior, but this particular morning I was witness to a new activity, namely a game of tag.

The resident Beaver spent the better part of half an hour chasing ducks around its pond. A pair of Mallards were subjected to this annoyance first. When approached, the Mallards would swim away together, with the drake quacking loudly, but obviously weren’t put out too much by this game as they tolerated it for about ten minutes before taking off (undoubtedly in search of a more serene body of water).

No sooner had the Mallards left than a pair of Hooded Mergansers arrived. The Beaver greeted the newcomers and proceeded to chase them around and around the pond, occasionally catching up to them, and then restarting the game all over again. Eventually the mergansers, too, departed, leaving the Beaver king/queen of his/her castle. (Thanks to Mike Keating for photo op.)

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Canada Geese Nesting On Beaver Lodges

4-29-19 c. goose on beaver lodge _U1A7241If you are fortunate enough to have a beaver pond near you, you should give the lodge more than a cursory glance this time of year. It is common to find Canada Geese nesting on beaver lodges, for obvious reasons – safety from most land predators. While Common ravens have been known to raid Canada Goose nests for eggs and goslings, the overall rate of survival of the goslings of lodge-nesting geese is very high.

A Canadian study showed that ponds with beaver lodges (and therefore Beaver activity which warms the water and thaws the ice) thaw at least 11 days sooner than ponds without Beavers, allowing early access to water for Canada Geese returning for the spring nesting season. Battles between pairs of geese vying for these coveted nesting sites are not uncommon.

Canada Geese have much to thank Beavers for. Not only can geese get an early nesting start on beaver lodges, they have a relatively safe spot to incubate their eggs and raise their young.

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Muskrats Cohabit With Beavers

4-24-19 muskrat_U1A7137Muskrats, or “rats,” as they’re sometimes derogatorily called, are semi-aquatic, mostly plant-eating rodents that live in ponds, streams, lakes and marshes. During the winter they seek shelter in lodges that they build out of grasses, reeds, cattails and sticks. Muskrat lodges are much smaller than Beaver lodges, which are constructed out of mud and sizable branches, sticks, stones and mud.

In the spring Muskrats often build nests by burrowing into a stream or pond bank, which they enter under water. Muskrats are also known to set up residence in active Beaver lodges. After dining on aquatic vegetation, the pictured Muskrat made a beeline for the beaver-occupied lodge nearby, and dove under as it approached it. Beavers and Muskrats tolerate each other’s presence in the same pond (and lodge) even though they both consume much of the same vegetation. Unlike Beavers, Muskrats supplement their diet of plants with frogs, crayfish, clams, snails, and fish. It may be that when cohabiting a lodge, they may help one another keep an eye out for predators. (Photo: Muskrat eating pond vegetation)

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