Wild bears exhibit adaptability in their diets, consuming a wide range of foods based on species, location, and season. This flexibility allows them to thrive in diverse habitats, from the Arctic to temperate forests. Their foraging strategies are dynamic, reflecting varying food availability. This opportunistic approach is central to their survival.
Diverse Diets Across Bear Species
Bear diets vary significantly among species, reflecting their adaptations and ecosystems. Polar bears are carnivores, primarily eating seals. They efficiently metabolize fat, which is important for insulation and energy. While mainly consuming ringed and bearded seals, they also hunt or scavenge other marine mammals like walruses, narwhals, and beluga whales. Birds, fish, or vegetation contribute minimally to their caloric needs.
Giant pandas are specialized herbivores, with bamboo making up over 99% of their diet. They consume bamboo shoots, leaves, and stems, requiring large quantities—up to 84 pounds (38 kilograms) per day—due to bamboo’s low nutritional value. Despite being classified as carnivores, their digestive system and nutrient intake from bamboo resemble hypercarnivores.
Most other bear species, such as black and brown bears (including grizzlies), are omnivores. Black bears typically derive 75% to 90% of their diet from plants, including grasses, berries, roots, insects, fish, and carrion. Brown bears also have a varied diet, often with plants constituting 80% to 90% of their intake in inland areas. They consume a wide array of items, including berries, grasses, roots, nuts, insects, fish, and small to large mammals.
Seasonal Shifts in Foraging
Bear diets change throughout the year, adapting to seasonal food availability. After emerging from hibernation in spring, bears focus on protein-rich foods to rebuild muscle. Their early spring diet includes fresh, tender vegetation like grasses, sedges, and new shoots, which are easier to digest. They also scavenge carrion and may prey on young ungulates like fawns or calves.
As summer progresses, soft fruits and berries become a significant part of their diet. Bears consume berries like strawberries, blueberries, and raspberries, which provide sugars and aid weight gain. Insects, such as beetles, ants, and their larvae, also become abundant protein sources. Some bears, particularly those in coastal regions, capitalize on early fish runs.
Fall marks hyperphagia, a period where bears intensify feeding to accumulate fat for hibernation. Their diet shifts towards high-calorie foods like nuts, including acorns, beechnuts, and hazelnuts, along with late-ripening berries. Bears living near salmon-spawning rivers consume large quantities of fish, prioritizing the fat-rich skin and blubber. This consumption leads to significant weight gain, with some bears doubling their body weight in months. During winter, most bear species enter dormancy, relying on these stored fat reserves.
Common Food Sources
Wild bears consume diverse food items: vegetation, insects, fish, and mammals. Plant matter forms a substantial portion of their diet. This includes vegetation such as grasses, fresh shoots, leaves, roots, tubers, bulbs, and flowers. Berries, including blueberries, raspberries, huckleberries, and buffaloberries, are sought after, as are nuts like acorns, beechnuts, and pine nuts.
Insects are a common food source, providing protein and fat. Bears frequently consume ants, beetle larvae, wasp larvae, and grubs, often overturning logs or rocks to access them. Honey is also eaten. Fish, particularly during seasonal spawning runs, are a significant dietary component for many bear populations, with salmon and trout being common prey.
Bears also prey on and scavenge mammals. Small mammals like rodents, squirrels, and marmots are part of their diet. Larger prey includes young or weakened ungulates such as deer fawns, moose calves, and elk calves. Carrion is consumed whenever available, including winter-killed animals or leftovers from other predators. Birds and their eggs also provide occasional food.