Brown bears have a varied diet that includes many types of food. In this article, I look at what makes up the diet of a brown bear.
Brown bears are omnivores and will eat whatever is edible and available. Brown bears eat mammals, small reptiles and amphibians, fish, plants, fruits, nuts, berries, and insects. They will also feed on human food and will rummage through trash.
This article examines what food brown bears need to fuel their large bodies.
What Do Brown Bears Eat?
Although classed as carnivores, brown bears are omnivores and will eat almost anything. Being the apex predator in their habitat, brown bears will eat most animals, including mammals, reptiles, amphibians, insects, and fish.
They also eat a lot of fruit, nuts, and berries. Bears that are close to humans will also eat human food from trashcans.
How Much Food Do Brown Bears Need?
Being such large animals, brown bears require an enormous amount of food to fulfill their dietary requirements and supply them with energy. When actively feeding, grizzly bears can eat between eighty to ninety pounds of food per day.
Brown bears eat more in the fall than in the spring when they awaken after hibernation. Brown bears need time to eat again once hibernation has ended. The digestive system takes a few weeks to start working correctly.
Which Mammals Do Brown Bears Eat?
The diet of a brown bear depends on its geographical location. Brown bears are classed as carnivores, and they eat both small and large animals.
An adult brown bear can take down large mammals such as caribou, deer, moose, and muskox. However, grizzly bears will take down an injured, old, young, or weak individual to conserve energy.
Brown bears also use their claws to dig squirrels and voles from their burrows, especially in spring after hibernation. Around this time, once the snow has melted, grizzly bears can feed on animals that have died during the winter.
Carcasses of bison, deer, elk, and moose that have not survived the winter months are essential for bears to feed on in early spring.
Brown bears feed on the young calves of caribou, deer, elk, and moose between May and June. Grizzly bears learn where the calves are born.
These areas stay the same each year, allowing the bears to return to them to prey on the young. Elk makes up a large portion of a brown bear’s diet in these months.
Which Fish Do Brown Bears Eat?
The amount of meat a brown bear eats will depend on whether the grizzly bears have access to a constant fish supply.
Brown bears feed on salmon that are spawning. Bears with access to spawning fish consume as much as 75% of fish in their diet. Without a supply of spawning fish, the amount of meat consumed can be less than 10%.
Brown bears have been seen to eat up to 40 salmon a day, totaling 100 pounds of salmon daily.
During summer, brown bears in Alaska and British Columbia will feed primarily on salmon. Bears in those areas will travel long distances to feed on the spawning salmon.
During July, salmon move through the rivers and lakes of Brooks Falls in Katmai National Park in Alaska. Salmon make a feast for the bears as it is one of the first streams that the pre-spawned salmon enter.
Although grizzly bears are known for eating salmon, they will feed on other fish species, such as trout, when available.
The amount of fish the bear eats depends on the time of the season. At the start of the spawning season, the bears will eat all parts of the fish. Later on in the season, they will eat the fatty parts and throw away the rest.
Which Plants Do Brown Bears Eat?
Although brown bears survive mainly on meat and fish, they also eat plants. The intestines and digestive tract of the grizzly bear are short, which helps them process food quickly.
Tender plants can be processed through the system in just over seven hours. Knowing the limitations of their digestion system, brown bears prefer to eat young, leafy plants rather than mature plants.
Brown bears will eat forbs, fungi, grass, and tubers as part of their diet. They will also eat the bulbs, corms, and roots that grow beneath the surface. Brown bears have long claws, allowing them to dig plants up easily. Some plants, such as biscuit root and sweetvetch, are essential to provide nutrition to the bears.
When they wake up from hibernation, plants make up a large part of the bear’s diet. In spring, when bears awake, the plants begin to grow. The snow melts quicker at lower elevations, and bears use this to their advantage. Bears stay at lower elevations to feed before moving up to feed on the new, softer grasses when the snow melts.
Which Insects Do Brown Bears Eat?
Grizzly bears eat insects as a vital part of their diet. Brown bears eat earthworms, wasp nests, ants, and beetle larvae. They feed on moths, especially during the summer months. Grizzly bears can eat up to 40,000 moths in a day, making the moth a critical food source.
With each moth containing half a calorie, a bear must eat a vast quantity to consume enough calories. Although low in calories, a bear can eat six months of calories in a single month from feeding on moths.
Hundreds of thousands of army cutworm moths, also known as miller moths, live in Yellowstone National Park, migrating from the lowlands to feed on the wildflowers that grow in the National Park. During the day, the army cutworm moths live in boulder fields under rocks on the mountain slopes.
Thousands of army cutworm moths sleep under the rocks in a boulder field, burrowing into the rockslides to avoid sunlight. This allows the bears to feast on large amounts of these moths. Brown bears are strong animals and can turn over rocks and boulders. This will enable them to feed on many hundreds of moths at once.
Bears do not generally share their territories, but they tolerate each other when there is plenty of food.
With the reduction of garbage dumps in the 1980s, some researchers believe that the brown bears in the Yellowstone area started eating more moths to replace the lost food source.
Which Fruit and Nuts Do Brown Bears Eat?
During the late summer, brown bears come down to lower elevations to eat fresh berries. Chokecherries, huckleberries, raspberries, cherries, and rose hips provide extra calories for the bears in warmer months.
Bears eat these sugar-laden berries during the fall to gain weight before hibernating. When there is less food in the wild, bears are more likely to raid farms looking for fruit.
Brown bears also feed on nuts, with the whitebark pine tree’s nuts being an excellent food source. Although the whitebark tree’s pine nuts grow high and out of reach, brown bears will raid nuts harvested by squirrels. Yellowstone National Park and Grand Teton National Park.
References and Further Reading
NPS.gov – Brown bears
Journal of Mammalogy – Brown Bear Food Habits at the Border of its Range
KTOO.org – Bears eat far more berries than you might think
USDA – The importance of meat, particularly salmon, to body size in brown bears