The American Black Bear (Ursus americanus) is an opportunistic omnivore whose diet is remarkably varied and dictated by what is readily available in its local environment. This feeding flexibility allows the black bear to thrive in diverse habitats across the continent. The specific components of its diet constantly shift, depending on the time of year and the proximity of human activity.
The Diverse Natural Diet
The bulk of a black bear’s natural diet is composed of plant matter. These bears are highly effective foragers, seeking out nutrient-dense vegetation to meet their considerable caloric needs. They consume a wide variety of soft mast, which includes the fruits of numerous shrubs and trees, such as serviceberries, blueberries, blackberries, and raspberries.
Black bears also rely heavily on hard mast, which refers to the nuts and seeds of forest trees. Acorns and hickory nuts are particularly important due to their high caloric and fat content. Beyond fruits and nuts, bears will also dig for roots, bulbs, and corms. They graze on succulent grasses and forbs, especially in the spring when new growth is tender and protein-rich.
Animal matter provides a crucial source of protein and fat, though it typically makes up a much smaller portion of the overall diet. Insects are a dietary staple, with bears routinely tearing into ant mounds, bee nests, and rotting logs to consume protein-packed larvae and grubs.
Black bears are not skilled predators of large adult animals, but they readily scavenge carrion left from winter kills or the remains of other predators. They also opportunistically target small vertebrates, such as fish and rodents. Bears may also prey on the young of larger animals like deer fawns or elk calves, especially in the spring when they are born and less mobile.
Seasonal Shifts in Foraging
The black bear’s diet is intrinsically tied to the seasons, changing to meet the need to prepare for winter denning. When bears emerge in the spring, they are in a negative energy balance and seek easily digestible foods to recover lost weight. This early-season diet consists of new, tender plant sprouts, grasses, and any available winter-killed carrion or insect colonies.
As the season transitions into summer, the food supply becomes more abundant and diverse. Bears shift their focus to consuming soft mast, such as berries, which begin to ripen. This period is important for lactation in females and for all bears to recover fully and begin moderate fat accumulation.
The most intense period of feeding occurs in the fall, a state known as hyperphagia, meaning “excessive eating.” Bears enter this phase to rapidly build the fat reserves needed to survive the winter without food or water. During hyperphagia, a black bear may consume up to 20,000 kilocalories daily, often spending up to 20 hours a day foraging.
This fall diet is dominated by high-fat, energy-dense foods like hard mast, including acorns and beechnuts, which are far richer in calories than the soft berries of summer. The success of a bear’s denning period and a female’s ability to reproduce are directly linked to the amount of fat they can store during this period.
Foods Found in Human Environments
The opportunistic nature of the American Black Bear means they will readily exploit calorie-rich, easily accessible food sources found near human development. This behavior is a primary cause of human-wildlife conflict. Unsecured garbage and accessible dumpsters are among the most common attractants, offering a high volume of diverse food items.
Other readily available food sources include outdoor pet food, which is often high in fat and protein. Bird feeders, particularly those containing sunflower seeds and suet, are also major attractants. Bears have an exceptional sense of smell, allowing them to locate these food sources from great distances.
Agricultural settings also provide food, with bears sometimes consuming cultivated crops like corn, oats, and orchard fruits. While these human-associated foods are often high in calories, they are frequently nutritionally unbalanced compared to a natural wild diet. Repeated success in finding these easy meals can lead to the habituation of bears, causing them to associate human dwellings with a reliable food supply.