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Black Bear Lactation

2-11-16  black bears IMG_0380Black Bear cubs are born in late January or February, weighing about eight ounces. The newborn cub(s) immediately crawl to their mother’s teats (she has six) closest to her pelvis to nurse. Later, as the cubs get older, they nurse from the top four and the mother often “switches off” production in the bottom two. At birth a Black Bear cub weighs half to three-quarters of a pound, and when it emerges from the den in April it averages about six pounds.

Most hibernating mammals are not pregnant. The fact that Black Bear cubs are born in late January or February, and the mother bear nurses them for two or three months while she is not eating or drinking is a phenomenon in and of itself – just ask any ravenous nursing human mother.

Milk production and intake increases four-fold after the cubs emerge from the den. At peak lactation (June and July) a black bear cub consumes about 30 ounces of milk a day. If a bear has two or three cubs, that means she must produce two or three quarts of milk a day. The milk of Black Bears is very rich: human (and cow) milk is about three to five percent fat while Black Bear milk is around 20 to 25 percent fat. In addition, the carbohydrate composition of the Black Bear mother’s milk while she is nursing in the den is relatively high compared to the carbohydrate composition found in milk after denning; the protein content after denning is double that of milk produced during hibernation.  At roughly six to eight months of age, Black Bear cubs are weaned. (Thanks to Ben Kilham for photo op.)

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10 responses

  1. Peggy Timmerman

    In the first line, did you mean eight ounces?

    February 12, 2016 at 7:45 am

    • Yes! Thank you for catching that typo!

      February 12, 2016 at 8:30 am

  2. robertwyatt

    Aren’t you glad that you’re not a bear who must produce that much milk each day?!! Could you have done that?


    February 12, 2016 at 8:07 am

    • My daughter is nursing her eight-month old son and she eats voraciously in order to do so, so the thought of doing that for two or three offspring with no food intake boggles my mind!

      February 12, 2016 at 8:31 am

  3. Evergreen Erb

    You have some conflicting information about the weight of the bears when they are born. I believe it is only ounces, not eight pounds. Loved the information though.

    February 12, 2016 at 8:57 am

    • Kathie Fiveash

      Fascinating how the different nipples can make different milk. I know that a mother kangaroo can actually have two babies in her pouch – one a tiny embryonic baby, the other a big joey. Each one feeds from a different nipple each nipple making a totally different formula of milk.

      February 12, 2016 at 6:53 pm

      • Wow, I had no idea that kangaroos had that arrangement, Kathie! Fascinating!

        February 12, 2016 at 8:15 pm

  4. Did you take this photo? Weren’t you nervous Mama would wake up?

    February 12, 2016 at 9:39 pm

    • Yes, I took it, but I was with researchers who had tranquilized the mother in order to weigh and take measurements on the cubs, so knew I was in no danger!

      February 12, 2016 at 11:08 pm

      • Good to know! 🙂

        February 13, 2016 at 5:16 pm

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