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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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8 responses

  1. Viola

    Very interesting, Mary, and these facts are particularly so because I lived for 25 plus years pond side where there was a lot of beaver activity. Many thanks, as always, for the fascinating information you provide.

    March 13, 2023 at 9:29 am

    • You’re so welcome, Viola! They are my all time favorite rodents!

      March 13, 2023 at 12:38 pm

  2. Alice

    So enjoyable to learn about all the animals.

    March 13, 2023 at 9:36 am

  3. A couple of years ago when i was regularly watching a beaver lodge at dawn – sometimes I saw as many as 9 beavers at a time swimming around – I watched and filmed a few aggressive interactions between beavers. I thought it was a parent trying to drive off 2 year old young. I sent you a movie by email, which you are free to share.

    March 13, 2023 at 10:10 am

    • Thank you so much, Kathie! Fascinating!

      March 13, 2023 at 12:39 pm

  4. So glad you enjoy the posts, Alice!

    March 13, 2023 at 12:38 pm

  5. Karen Eger

    Definitely take a whiff of the mound as it is a very intense and strangely memorable smell. You can smell it in the air on a humid day.

    March 14, 2023 at 6:14 am

  6. Jonathan Byrd

    A belated thank you for this post, Mary. We live on a pond, and the beavers, which always have been here, have been highly active over this past fall and winter. They have cut down many saplings, small trees, and bushes at the edge of our lawn and pond and used them to enlarge their home. We have seen these territorial markers and have always wondered why the beavers made them. We also have a couple of otters, but we don’t know where they live. So far, the beavers and otters are living harmoniously

    I’ve attached a couple of videos of the beaver’s activity from a few weeks ago. We have some game cameras set up to watch them! Lots of fun.

    Thanks again,


    March 21, 2023 at 8:46 am

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