Bears are diverse mammals inhabiting a range of environments across the globe. A single “favorite food” for bears is an oversimplification, given the variety among bear species, their distinct habitats, and their adaptable dietary needs. Their feeding behaviors are highly flexible, allowing them to capitalize on available resources in their specific surroundings. This adaptability is fundamental to their survival.
The Varied Diets of Bears
Most bear species exhibit omnivorous feeding habits, integrating both plant and animal matter into their diets. The American black bear, for instance, consumes a wide array of foods, including grasses, berries, roots, succulent plants, insects, and fish. Plant-based foods can constitute a significant portion of their diet, sometimes up to 85%. Occasionally, they may also prey on young ungulates, such as deer fawns or moose calves.
Grizzly bears, a subspecies of brown bears, are also omnivores, and their diet changes depending on the season and specific region. In many inland areas, plant matter like roots, grasses, berries, and nuts account for 80% to 90% of their food intake. They supplement this with insects, small mammals, and carrion. Coastal grizzly populations, however, frequently rely on anadromous fish, particularly salmon, during spawning seasons.
Polar bears are the most carnivorous of all bear species, primarily subsisting on ringed and bearded seals. The high fat content of seals provides necessary energy and insulation for their survival in the Arctic’s cold environment. While they may scavenge whale carcasses or consume birds and eggs, these food sources are less calorically dense and do not form the bulk of their diet.
Giant pandas maintain an almost exclusively herbivorous diet, with bamboo comprising over 99% of their food intake. Due to the low nutritional value of bamboo, a panda must consume between 26 to 84 pounds (12 to 38 kg) of it daily to meet its energy requirements. Although primarily vegetarian, they occasionally consume other plants, fruits, or even small rodents, but these are minor dietary components.
Seasonal Influences on Bear Diets
Bear diets show considerable adaptation throughout the year, driven by the changing availability of food sources. In spring, as bears emerge from their dens, food is initially scarce. They primarily forage on new plant growth, such as grasses, sedges, and forbs, and may also scavenge carrion from animals that perished during winter.
During the summer months, soft fruits and berries become widely available, forming a substantial part of the diet for many bear species. Black bears also consume various insects like ants and wasps during this period. Grizzly bears can eat large quantities of berries, such as huckleberries and buffaloberries.
As fall approaches, bears enter a phase known as hyperphagia, where they consume large amounts of food to accumulate fat reserves for the upcoming hibernation period. Mast crops, including acorns and beechnuts, become an important food source.
Diet and Bear Well-being
A natural and varied diet is important for a bear’s overall health, supporting their growth and preparing them for the rigors of hibernation. The accumulation of significant fat reserves in the fall, largely from energy-dense foods like berries and fish, supports winter denning and successful reproduction. Bears are able to accumulate 30% to 40% body fat, which is a healthy state for these animals.
When bears consume human-provided foods, negative consequences can arise. Bears that become accustomed to human environments frequently seek out readily available sources such as garbage, pet food, or agricultural products. Such diets, which often contain high amounts of processed sugars, can lead to nutritional imbalances and a reduction in the diversity of their gut microbiome. This dietary shift can impair their ability to efficiently digest natural foods if they return to a wild diet.
Research indicates that bears consuming human foods may experience shorter hibernation periods, which could contribute to accelerated cellular aging and potentially a reduced lifespan. To promote the well-being of both bears and humans, it is important to eliminate the availability of human food waste in natural bear habitats.