Getting ready to bear down for winter

We could see it moving through the tall, dull green grass of late summer, and it was heading in our direction. I told the group we should move back and get our cameras ready. It looked like it was walking directly toward us, and it was a big one. Then I told the group, “For this image to work, we need to get down low and switch from horizontal to vertical format.”

Only a minute later, my prediction was correct: it was walking straight at us. Using a very long lens to maintain distance, the group captured some impressive images of a male American black bear (Ursus americanus). This particular bear was well over 500 pounds and was getting ready for hibernation.

The American black bear, usually called the black bear, is referred to as “American” because it is endemic (found only) in North America. Of the three bear species in North America, it is the smallest but the most widespread.

The black bear evolved from another bear species around 4 to 5 million years ago. Since that time, fossil records indicate the black bear has become smaller. Historically, the American black bear has roamed much of North America, but today, it is mainly found in the Northeast, down the Appalachian Mountains, and in northern states such as Michigan, Wisconsin, and Minnesota. It is also found throughout Canada, along the Rocky Mountains, and down the West Coast, extending into California.

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Adult male black bears typically weigh between 200 and 500 pounds, while adult females are smaller, averaging between 100 and 375 pounds. Black bears found in northern states and Canada tend to be larger than those in southern states. This follows Bergmann’s rule, which states that larger animals retain heat better in cold climates, while smaller animals can cool down more easily in warmer climates.

I find black bears utterly fascinating. These critters are perfectly adapted to living in North America. Bears can do things other animals can’t. For example, black bear mating season occurred back in June, yet even now, at the end of summer, the females are still not pregnant. Their reproductive system holds the egg and sperm in a suspended state, and the embryo doesn’t implant in the uterine wall until October. The female’s overall health in autumn determines how many fertilized eggs will develop into cubs, which will be born in February after only about a four-month gestation.

At this time of year, bears eat as much as possible to build enough fat to last through winter. Hibernation can only be described as amazing. In northern regions, a bear can hibernate for up to seven months. During this period, the bear’s metabolic activities are suppressed, and in some cases, such as with the digestive system, they come to a complete stop. Other systems, such as body temperature, only slow down. Respiration and heart rate also decrease. When these systems slow or stop, the bear conserves enough energy to survive until spring. Think of it like gasoline in a car; the more you conserve, the longer it will last.

Many people envision a hibernating bear as being unconscious, with its mouth open, tongue hanging out, and snoring loudly. In reality, bears are often awake, looking around, and attending to necessary tasks. They move regularly, and pregnant females give birth during hibernation. After the cubs are born, the mother keeps them warm and nurses them. Injured bears often heal during hibernation and are well-recovered by spring. If humans were to lie down for seven months, our muscles would atrophy so severely that we’d need to learn to walk again. Bears, however, hibernate for the same amount of time without suffering muscle loss.

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As you can see, bears are amazing creatures with abilities that other mammals do not possess. Until next time…

Editor’s note: Stan Tekiela’s NatureSmart column appears twice a month in the Eden Prairie Local News. Tekiela is an author, naturalist, and wildlife photographer who travels extensively across the United States to study and capture wildlife images.

You can follow his work on Instagram and Facebook. He can be contacted via his website at www.naturesmart.com.