About Bears
Ursus Americanus (American Black Bear)
The only species of bear the currently lives in the wild in the state. They ranges have changed over the centuries due to the increased inhabitance of Minnesota by humans. Today, black bears are generally restricted to forested areas. They follow their keen sense of smell, and develop mental maps of their landscapes to locate food sources, which are in a constant state of flux, from season to season and year to year. Because there is minimal food available for these large mammals during the Minnesota winters, they will hibernate. Black bears usually try to avoid people, but sometimes come in conflict with humans when they eat crops, destroy apiaries, break into birdfeeders, or find access to garbage for food.
General Description: A large black (or sometimes brown) mammal with a large head, small eyes, erect ears, stout legs, and a very short tail: they lack the shoulder humps of a grizzly or brown bear. Black bears have reasonable eyesight and hearing capabilities, and an exceptionally keen sense of smell (better than a canine).
Length; Typically adults can be five to six feet long.
Weight: Full grown adults vary in weight from 150 (small female) to >500 (large male) pounds.
Color: Black, dark or light brown (in Minnesota, less than 10% are brown). Some will have a chest blaze.
Sounds: Bears make huffing, snorting, and jaw-popping sounds when nervous or distressed, trying to repel intruders; cubs make humming sounds when nursing (an indication of being satisfied), and squealing when frightened or uncomfortable.
For more information see the DNR’s Black Bear website.
Frequently Asked Questions
Do bears really hibernate?
Hibernation is defined as a state of inactivity and metabolic depression in animals and is characterized by lower breathing rate, decreased body temperature, and/ or decreased metabolic rate. Hibernation conserves energy when food is in short supply during the winter months. With this definition, black bears in Minnesota can be considered as hibernators, since they go into hibernation typically from November to the beginning of April. Bears in warmer areas may not hibernate, but this will depend of birthing and the availability of food.
Black bears have the unique ability to hibernate for 5-7 months of the year. Their body temperatures drop by approximately 2-4 degrees Celsius from their normal temperatures. During hibernation, bears rarely will eat, drink, urinate, or defecate.
During hibernation, bears lose less than 10-20% of their strength over 130 days. In comparison, under similar conditions of inactivity, it is predicted that humans would lose 90% of their strength over 130 days: assuming they still are eating and drinking too. Bears are capable of "turning over muscle;" while they are hibernating.
Black bears will go into a den of sort and hibernate during the winter months because of a lack of food. The duration of hibernation greatly depends on location. Bears in warmer climates with abundant food sources may not hibernate at all unless a given female is birthing.
Black bears in Minnesota use several different types of dens. The most common are nests, excavations, and tree roots. Bears have also been known to use drainage ditches and man-made culverts as their dens. Males always hibernate by themselves, and females will hibernate with their cubs until they are yearlings. Bears typically do not re-use their dens from the previous year. It is also very uncommon for bears to use another bear's den. On rare occasions yearlings will go back to a previous den.
right: Mother and cub utilizing an excavation; left: bear hibernating in a nest made of reeds.
Will black bears attack if you come near their dens?
Black bears generally avoid human contact and will not attack if you come near their dens, but they will defend themselves if you try to enter their dens. To do so, black bears make huffing, snorting, and jaw-popping sounds when nervous or distressed. Other types of bears, such as brown bears, have been described to attack if you approach their dens.
What do black bears eat?
The American black bear is both a generalist (eats a wide variety of foods) and an omnivore (eats both plants and meat). Yet, in Minnesota, a black bears' diets can be quite varied as the different habitats in which they live. In Minnesota, after leaving their dens, bears seek out emergent spring vegetation such as horsetail, sedge, and aspen buds. As these spring plants become less nutritious in late spring, they tend to eat ants. Ants (and ant pupae) are abundant and provide a source that is high in protein. Rarely, bears in Minnesota will also utilize other high-protein sources of food, such as deer fawns. During the height of summer, bears hone in on berry species as they become ripe. Bears in Minnesota eat everything from raspberries to wild plums. In the fall, bears need to consume calorie-rich diets to prepare for hibernation; this time of intense feeding is known as hyperphagia. Typical fall foods include hazelnuts and acorns, while some bears living in close proximity to agriculture will supplement their diets with corn, oats, and sunflowers.
Are bears social animals?
Minnesota black bears are not typically social animals, however, females will stay with their cubs for a year before mating again (a two year cycle).
What is Ecology and Conservation Biology?
Black bears live in several different areas around the United States, including most of the Northeast, Midwest, Rocky Mountain Range, west coast, and Alaska. Minnesota black bears mostly reside in the upper third of the state. They generally live in forests, swamps, and other areas with protective cover, but often feed in open fields where crops are grown.
Minnesota black bears do not have any natural predators except for humans. Approximately 3,000 bears annually are shot by hunters. Hunting licenses are available from the Department of Natural Resources (DNR), however it is strictly prohibited to shoot a black bear that is wearing a brightly colored radio collar. Currently, several hundred bears are tracked by the Minnesota DNR each year to obtain sample populations. Integrated population modeling has been utilized by the Minnesota DNR to construct sex-specific age at harvest matrices. This research demonstrates a robust and viable population monitoring program in Minnesota.
Reference:
Fieberg JR, Shertzer KW, Conn PB, Noyce KV, Garshelis DL: Integrated population modeling of black bears in Minnesota: implications for monitoring and management. PLoS One, 5:e12114, 2010. PMID: 20711344 PMCID: PMC2920827 DOI: 10.1371/journal.pone.0012114
How is bear research conducted?
Black bears are able to emerge from hibernation very quickly and maintain most of their muscle mass over the wintering months. Because of this, adult bears and yearlings must be anesthetized before removing them from their dens for research. Bears are given anesthetic by one of two methods:
- jab pole- the syringe is attached to a stick or tent pole and administered into the musculature of the bear
- dart gun- darts containing the anesthetic are shot from afar.
Once the bears are weighed and the physiological parameters are obtained, the bears are placed back in their dens.