January / February Is Birthday Time For Bears - BearWise

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January / February is birthday time for bears

The fact that bears mate in summer and give birth seven or eight months later might make you think that bear pregnancies aren’t all that different from human ones. But even though bears mate in summer, they’re not officially pregnant until late fall. Nevertheless, they give birth a few short months later, in January or February.

Why Bears Have a Two-Step Pregnancy

Mother Nature has engineered a unique two-step pregnancy process for bears. During step one (mating), eggs are fertilized, but don’t implant or begin to further develop. Several months later, development (step two) begins when the fertilized eggs finally implant. This process is called delayed implantation.

Implantation is delayed because if the bear is underweight, sick or injured, the fertilized eggs may not implant or develop any further. Instead, the eggs can be reabsorbed in order to give the bear the best chance to survive and breed again.

During late summer and fall, an almost-pregnant bear works very hard at gaining as much weight as she possibly can so she has enough fat reserves to sustain herself and produce an abundant supply of the rich milk her cubs will need to fully develop. Then it’s on to step two. Implantation generally occurs and development begins in earnest once the bear is safely tucked into her den.

Bear biologist Adam Hammond examines a newborn bear cub near the den (courtesy of Georgia Department of Natural Resources).

From Newborn to Furry Bear Cub

Black bear cubs usually weigh in at under a pound, far less as a percentage of mom’s weight (less than 1/150th) than most mammals, including humans, where it’s normal for a 140-pound woman to give birth to an 8-pound bundle of joy that weighs in at five percent of Mom’s weight.

At birth, cubs’ eyes and ear canals are closed. The tiny cubs are covered in a coat of exceptionally fine, short hair; their teeth have yet to emerge. But cubs are born with a strong survival instinct. They quickly snuggle up to their mom and siblings to stay warm and settle in to feast on a steady diet of highly nutritious milk. Bear cubs love to eat; they make happy purring, humming noises while they are suckling.

It’s the perfect recipe (super-rich food and little activity) for packing on four to eight pounds before tumbling out into the world about thirteen weeks later, usually sometime in April or May.

black bear cubs in den; photo by Rich Beausoleil, Washington Dept of Fish & Wildlife)

The bright-eyed cubs in this photo taken by Washington’s state bear specialist Rich Beausoleil are 73 days old. What a difference from the newborn cub that Georgia’s bear biologist Adam Hammond is holding.

When they’re about six weeks old their bright blue eyes and ear flaps open. About ten days later teeth erupt. As they continue to grow, their fine hair becomes a protective fur coat. By the time they emerge from their snug winter dens, the furry bear cubs have razor sharp little teeth and claws; they’ll be able to climb a tree lickety-split before they’re three months old.

How many cubs are born? Typically, two to three, but there can be as few as one, or rarely, as many as six. Exceptionally large litters can be a sign that mom’s been eating a steady diet of super-fattening human-provided foods and will most likely soon be teaching her cubs to seek out those same familiar food sources. Just another good reason to make sure all your attractants are safely stowed away before bears wake up and go exploring.

Main photo: Born in January, these three bear cubs with sharp little claws are approximately 7 to 8 weeks old, snug in the den with mom (courtesy of Emily Carrollo, Pennsylvania Game Commission).

Click to learn more about black bears

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January / February Is Birthday Time For Bears - BearWise