Out in the Woods

A black bear checks out one of its easiest food targets, bird feeders.

Photo: Kevin McKeon

Black Bears: Hungry, Not Hazardous

By Kevin McKeon, Maine Master Naturalist

Black bears have been in North America for about 3 million years, since their ancestors crossed the Siberian/Alaskan land bridge from Asia. They’re the smallest of the North American bears, which also include polar, brown, and grizzly bears. During the last 150 years or so, these bears have enjoyed a return to historic population levels as abandoned fields and pastures return to forest habitats.

All of the estimated 55,000 bears living in the Northeast are black bears, and about 35,000 live in Maine — more than in any other state east of the Mississippi. Alaska has the most, with about 100,000.

Black bears prefer large, undisturbed, relatively mature spruce-fir and oak-hickory-beech forest landscapes but have adapted to human development, learning that messy humans often leave attractive food sources in garbage dumps, rural dumpsters, barbecue picnic residue, and bird feeders. They’re largely vegetarian, and up to 90% of their food consists of nuts, acorns, fruits, and vegetation. They rarely kill for themselves but will scavenge from the kills of others.

Generally considered to have one of the best senses of smell in the animal kingdom, black bears can easily sense a bird feeder from over a mile away, according to the National Park Service. (Their cousin, the polar bear, can smell a seal under the ice from half a mile away!) Bloodhounds smell about 300 times better than we do, and black bears smell seven times better than bloodhounds. This sense is used for foraging for all kinds of food: fruits, berries, nuts, roots, bulbs, grasses, insects, fish, meat, garbage, nesting birds, carrion, and the occasional hunted mammal or fish. From rural and farm areas and trash cans they’ll forage for blueberries, corn, honey, livestock, fish and food scraps.

Unlike grizzly bears, black bears rarely attack humans, causing fewer than one death every three years from over half a million black bears, according to the National Center for Health Statistics. For every death caused by a black bear, 17 deaths are caused by spiders, 25 from snakes, 67 from dogs, and 180 from wasps and bees.

Black bears don’t growl. They use grunts to communicate with other bears and will blow loudly and chomp their teeth to signal their fear of us. They’ll leave scented tree scratchings as territorial markings. Cubs will scream when distressed but hum when happy. They can run as fast as 25 miles an hour, and with curved front and straight rear claws have a superb climbing ability. Adult males grow from 250 to 600 pounds; females average 100 to 400 pounds. Males measure five to six feet in length from the tip of their nose to the tip of their tail; females average four to five feet in length.

Black bears aren’t true hibernators but have evolved a form of dormancy called torpor to cope with winter’s food scarcity. In December, they build dens in large tree cavities, overturned stumps, and caves, lined with leaves, twigs, and branches. The lone bear or mother with yearling cubs will then enter torpor. During this four-month deep sleep, heart rates drop to about 20% of normal and metabolism to 50%. They are sustained by stored body fat and protected by thick pelts, but sometimes leave the den during short, warm periods, or when calamity strikes nearby. A few years ago, a mother and cubs were chased from their den by logging operations in the Hanson Ridge area.

In January, one to four cubs weighing less than a pound are born with a light covering of fur. At two to three months, cubs can leave the den with their mother, who has sole responsibility for their survival. But about half of all black bear cubs succumb to starvation. Those that make it to one year old have a 90% survival rate, after which most deaths are caused by humans. The adults will emerge from their sleep with up to a 30% weight loss, but with no muscle or bone loss — an adaptation under study to address possible wasting diseases in humans.

Bear at feeder video: https://youtu.be/A3Ss2hE3omY

Editor’s note: Did you see something unusual last time you were out in the woods? Were you puzzled or surprised by something you saw? Ask our “Out in the Woods” columnist Kevin McKeon. He’ll be happy to investigate and try to answer your questions. Email him directly at: kpm@metrocast.net