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Beavers Breeding

2-6-19beaverimg_3683Beavers are in the middle of their breeding season, which means copulation takes place under the ice, undetected by human eyes, making information about their reproductive habits hard to come by. What is known about the breeding practices of North America’s largest rodent is that beavers form permanent breeding pairs and are monogamous through consecutive breeding seasons. Should a beaver’s mate die, a new one will take its place. In a colony, only the adult (individuals which are at least three years old) pair breeds. Mating usually takes place in January or February, and typically occurs at night in the water. Gestation is roughly 128 days and three or four kits are born in May or July.

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11 responses

  1. Alice Pratt

    Beautiful photo, with it’s reflection!

    February 6, 2019 at 9:03 am

  2. Deborah Luquer

    GREAT pic

    February 6, 2019 at 9:12 am

  3. Kathie Fiveash

    How did that fellow or gal get out from under??

    February 6, 2019 at 10:03 am

    • Hi Kathie,
      The photo was taken last April! Best I could do, as I don’t have an underwater camera!

      February 6, 2019 at 6:06 pm

  4. Betsy Janeway

    Dear Mary, I think yiu meant May or JUNE, right? Betsy

    February 6, 2019 at 10:50 am

    • You’re absolutely right, Betsy, though they have been known to give birth in July, as well!

      February 6, 2019 at 6:11 pm

  5. Not sure where the 3 or 4 average kits being bred each year comes from, but in my admittedly limited experience, it seems more like 1 to 2 kits if lucky!

    February 6, 2019 at 2:26 pm

    • RIchard, in North America, the average number of young in a beaver litter is 3.8!

      February 6, 2019 at 6:14 pm

  6. Bruce S Thompson

    Hi Mary. I am a longtime beaver fan. Thanks for your latest piece. My sources indicate that our beavers in Wyoming are in estrus January-February for 12-24 hours, giving birth in April-May, with a gestation period of 100-110 days. Would you share your source for the specified 128 day gestation period? Perhaps some of my information (teaching about beavers since the 80’s!) needs updating. I am also of the understanding that while lifelong bonding is the norm, genetic studies have revealed some liters as having been sired by two or more males, and that inbreeding has occurred within isolated, highly social groups.

    February 6, 2019 at 6:38 pm

    • Hi Bruce,
      Thank you for writing. I believe you are absolutely correct about beaver gestation period , at least according to Dietland Muller-Schwarze and Lixing Sun in their book The Beaver. Although there is reference to a 128 day gestation period in this book (Patterns of Mammalian Reproduction by S.A. Asdell, 1964), all my other sources agree with you (one says as few as 98 days). I simply didn’t read carefully enough, and I also wrote July instead of June! Thank you for catching this.

      I agree with your genetic breeding findings, as well. I know someone who is intimately familiar with the beaver breeding on her pond and has studied them for decades. The head male mated with his daughter when his mate (her mother) disappeared.

      February 8, 2019 at 5:14 pm

  7. Char Delabar


    February 6, 2019 at 8:34 pm

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