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.
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.
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.
Bears Are Hard-Working Moms
Bears are amazing and dedicated moms. They spend the summer and fall industriously searching for food for themselves and their rapidly growing cubs, and patiently teaching the youngsters how to forage for food, find shelter and develop all the skills they will need for life on their own. Female bears mate every other year at most; cubs born this year will den up with their moms come winter and then strike out on their own the following summer, giving mom a chance to start a new family.
How You Can Help Cubs Grow Up
A cub getting into your garbage, bird feeder or pet food might seem cute and harmless, but the very best thing you can do to help cubs grow up and stay wild is to make sure you don’t teach them to associate people with food. Teaching bears to depend on human food creates nothing but problems for people and bears.
Download our free BearWise Basics flyer that shows you all the things around your home that might attract bears and gives you tips for being BearWise at home.
Please Don’t “Rescue” Cubs
Every year well-meaning people turn healthy bear cubs into orphans; please don’t be one of them. If you see a very small cub, don’t remove it from the area or try to “save” it.
When a mother bear senses danger – as in when a human or a predator is getting too close to her cubs – she will typically send cubs up a tree or leave them at the base of a tree and then leave the area to draw the danger away from her cubs. Bear biologists call these trees “babysitter trees.” Typically, the female will return to gather up her family when no people or pets are around, usually after dark. As the cubs get older and more mobile, it is common for a mother bear to leave her cubs to go forage for food (the kids are always hungry) as much as two miles away from them.
If you believe the cub is truly orphaned, do not touch it. Instead, immediately leave the area and contact your state wildlife agency for further guidance.