About Black Bears

Black bear © Karen Karlberg
Black bear © Karen Karlberg

The only bear species that makes its home in Massachusetts is the black bear (Ursus americanus). It is the largest meat-eating mammal in New England, occasionally reaching weights of 500 pounds.

Black bears are named the same as hogs—males are boars and females are sows, but babies are called cubs. In the wild they can live to be about 25 years old.

Population

Prior to 1952 black bears could be killed by anyone, at any time. Because of this practice, and the loss of their forest habitat, black bears were rare in the Commonwealth in the 1800s and early 1900s. That phenomenon is changing. Regulations passed in 1952 made it illegal to kill black bears except during regulated hunting seasons with a hunting license.

Due to this conservation effort, the Massachusetts Division of Fisheries and Wildlife estimate that in 2005 there were 3,000 bears in the Commonwealth, most west of the Connecticut River, and the number is rising at a rate of about 8 percent a year.

Behavior

Except for females with cubs, black bears are solitary animals, though several may be attracted to a food source, such as a landfill. 

Tree marking by male black bears is common, especially during the spring mating season. They stand on their hind legs and scratch the trees with their claws and sometimes their teeth. Also in the spring, bears rub against rough-barked trees to help them shed their winter coats, leaving snagged hair and rub marks in the bark.

When necessary, black bears can run 32 miles an hour and climb trees nearly as fast as a squirrel. They are great swimmers and love to play in water during the warm weather.

Although they are rarely seen, black bears are active during the day--most commonly at dawn and dusk. In the summer, they will often seek a shaded spot during the hottest time of the day to get out of the sun.

Home Range

Compared to other mammals, the home ranges of male black bears are far-reaching and vary according to the season and available food sources. The greatest distances are covered during the breeding season when males search for females. An adult male can cover an area of 122 square miles during the course of a year. On the other hand, a sow (female) with cubs stays within an area of only about 12 square miles and a barren female may remain in an area only 10 square miles annually.

Hibernation

Black bears are not considered “deep” hibernators. When bears enter the den, usually  between early November and mid-December, their body temperature, heart rate, and respiratory rate drop to conserve energy and help the bear survive the winter months. But, unlike the other hibernators, the black bear’s body temperature drops very slowly to about 88 degrees, only a slight change from its summer temperature of 100 degrees.

In comparison, a woodchuck’s body temperature drops to an average of 40 degrees during hibernation. The higher body temperature means that the bear can respond to danger much faster than animals with lower body temperatures. As with the other hibernators, the bear’s heart beat drops from 40 to 50 beats per minute to 8 beats per minute.

For 100 days, black bears do not eat, drink, urinate, or defecate. Urea, a waste product found in urine, can be fatal in high levels in most animals (including humans), but bears are able to break down the urea. The resulting nitrogen is used to build protein, which helps bears maintain muscle mass and healthy organ tissue during inactivity. During this time their stored body fat provides the nutrients and water they need during hibernation, which results in a 30 percent loss of their body weight.

Dens

Black bears typically den in caves, brush piles, depressions under fallen trees, or rock crevices. Occasionally a bear will just curl up on the ground and wait to be covered with snow. Except for mothers with cubs, bears den alone.

The temperature of the den varies depending on the snow cover and whether or not the entrance is open. Although some bears will make a bed of pine boughs, grasses, or leaves on the floor of the den, most dens provide little insulation and merely act as windbreaks.

Black bears rely on their thick fur, which doubles its insulating value in the fall, and the 3 to 4 inch layer of fat that they acquired during their summer and fall food consumption. Emergence from the den is determined by the availability of food, rather than weather conditions, and usually takes place in April.

Food

Black bears are omnivorous and consume a large variety of foods, changing their diet with the seasons. They eat berries, nuts, flowers, fruits, and succulent grasses (including corn) as well as insects, frogs, snakes, fish, and garbage.

Black bears also raid beehives for honey and bee larvae when available. As members of the Order Carnivora, Black bears will eat small mammals, birds (usually the offspring of ground-nesting birds), and animal carcasses, including white-tailed deer, when the opportunity presents itself.

They are attracted to neighborhoods in central and western Massachusetts by trash, bird feeders, and pet food left outdoors.

Life Cycle

Female black bears are sexually mature between three and five years of age and reproduce every other year. Breeding takes place during the summer, usually in June or July, when the males seek out and mate with several females.

In a process called delayed implantation, the eggs are fertilized; some cell division occurs, and then development stops. In the fall, the tiny ball of cells, called the blastula, attaches to the wall of the uterus and growth begins. Most of the development of the fetuses takes place during a six to eight week span culminating in the birth of one to three young in late January or in February while the female is hibernating.

At birth, the cubs are blind, hairless, and weigh only 8 to 10 ounces. The sow’s milk, containing over 20 percent fat, is very rich compared to human milk, which contains only 4 percent fat. The young grow quickly and when the sow and her cubs emerge from the den in April, the cubs can weigh 4.5 to 9 pounds. Although they continue to be nursed throughout their first summer, the cubs also begin eating solid food.

Cubs leave the mother following their second winter, when they are 16 or 17 months old. Young females are allowed to occupy portions of the mother’s territory, but the males are forced to move on to find their own territory. It is often these rejected, young males that wander into residential areas where conflicts with people sometimes occur. 

Situations & Solutions

Conflicts between people and bears are becoming more commonplace as land is developed in or near bears’ preferred habitats. As black bears lose their preferred feeding and denning sites to development, they must move greater distances to find food (and often in residential areas). Find out how to keep black bears away and what to do if you encounter one