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Beavers Posting Their Land

It’s not as neat nor as tall a mound as it typically is, but the vegetation you see on the bank of this pond is a beaver’s way of posting its territory.  In two to three months, around the time that beavers give birth, the two-year-old beavers inhabiting a lodge typically leave to seek greener pastures in the form of unclaimed ponds or to form their own pond.  No-one is quite sure whether parents encourage this departure, or whether the young beavers take it upon themselves to leave, but especially when the food supply is limited, the two-year-olds disperse.

Older, established beavers, having experienced this exodus themselves when they were young, are well aware that two-year-olds will be scouting for a new spot to set up residence in the spring.  In order to discourage any potential intruders, beavers build one or more “scent mounds” on the shore of their pond or stream that consist of mud and vegetation they’ve gathered from the bottom of the pond or stream.  They then walk over these mounds and excrete liquid castoreum from castor glands (located near their anal glands) onto it.  The scent of castoreum is very distinctive and conveys information to beavers passing by that tells them that this location has been claimed and to move on. (If you come upon a scent mound, I encourage you to smell it – castoreum has, to some people, a very pleasing scent.)

Interestingly, castoreum contains salicylic acid, which is the active ingredient in aspirin. Salicylic acid is found in willows (which beavers eat), and native Americans used willow bark to treat headaches.

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Beavers Grooming

Beavers spend an inordinate amount of time grooming themselves (and each other). Both inside their lodge and on land a beaver tucks its tail between its legs, sits up on its hind legs and spends up to an hour at a time fastidiously combing through its fur often multiple times a day. 

Both front and hind feet are pressed into service.  The two inner toes on each hind foot are modified for grooming – the second toe has a “split nail” with a nail and a horny growth between the nail and the toe which has a finely serrated upper edge that serves as a fine-toothed comb.

Grooming serves two purposes.  One is to remove debris from the coat, from algae to burrs and parasites.  The other is to waterproof the beaver’s coat. A beaver applies an oily substance from its anal glands to the outer layer of hair with the help of its toes, thereby preventing its inner, denser, underfur from getting wet.

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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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