“I Didn’t Know I Was Pregnant:” The Fascinating Reproductive Cycle of Bears

All, Nature Notes
A female black bear stands in a tree with her two cubs.
Black bear family. Photo by Courtney Celley/USFWS Midwest Region

You’re cozy and warm, just waking from a long rest. A ray of shimmering sunlight illuminates your space, and you slowly smile. Revived and refreshed, you breathe deeply, taking in the scents of spring – wet, fertile earth, warmed by the sun; a warm breeze; buds breaking through the outer layers of bark at the ends of branches; baby bear cub s…

Wait, what?

You look down and realize that two babies have been using your body for food and warmth while you’ve been asleep. And they’ve been doing it for months, judging by their size and coordination.

Oh, and you’re a bear.

This is how many female bears wake up after their winter hibernation (at least, that’s how I imagine they do!). These amazing mammals go through a process called delayed implantation: Though mating season is in June and July, their bodies wait to implant their eggs until fall, and even then, only if mom has eaten enough food to last her through a healthy hibernation (technically called torpor when we’re talking about bears).

A young boy lays on top of a black bear belt.
Black bear pelt (boy included for size). Photo by Stephanie Morris

If a female bear eats enough food to trigger implantation, she goes to sleep in her den with no kids and wakes up with two or three!

The cubs are born while she’s in torpor. They birth themselves – about six weeks after implantation, which puts their birthdays in mid- to late-January. Right now, these cubs, who cannot see until they are 6 to 8 weeks old, are hanging out with their moms, drinking her milk and waiting for her to wake up in March or April.

Cubs stay with mom for the first 18 months of their lives, and then they go off on their own, finding their own habitat and mates.

A map of Ohio shows confirmed black bear sightings by county from 1993-2018.
Source: Ohio Division of Wildlife

Black bears are native to Ohio but are rarely spotted in Hamilton County. Because of the population density of the area, they likely won’t stay here, even if they stumble through on their way to find a suitable habitat – they need space, heavily wooded habitat and a papa bear to make their home.

Learn more about black bears from the Ohio Division of Wildlife.

Written by Nikki Ferrell with information from the Ohio Division of Wildlife and Great Parks Nature Interpreter Stephanie Morris.

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