Brown bears have a varied diet that includes many types of food. In this article, we look at what makes up the diet of a brown bear.
Brown bears will eat whatever is edible and available. Brown bears will eat other animals, fish, plants, fruits, nuts, berries, and insects, along with human food and discarded rubbish.
In this article, we break down what types of food these enormous bears need to fuel their large bodies.
What Do Brown Bears Eat?
The brown ‘grizzly’ bear is a huge bear that requires many different types of food. Although classed as carnivores, brown bears are omnivorous.
Being such large animals, brown bears require an enormous amount of food to fulfill their dietary requirements. Grizzly bears can eat between eighty to ninety pounds of food per day when actively feeding.
Brown bears eat more in the fall before hibernation than they do in the spring when they awaken. Like the black bear, brown bears take some time before they can eat again once hibernation has ended. The digestive system takes a few weeks to start working again once the grizzly bear wakes up.
The varied diet of the grizzly bear is helped by the teeth structure of the grizzly bear. Brown bears have some teeth that are similar to canine teeth. These teeth are sharp, which helps them with eating meat.
They also have molars, which allow them to eat and chew plant material. Grizzly bears are the most omnivorous bears in North America, as they eat more meat than black bears but less than polar bears. They also eat fewer plants than black bears but more than polar bears.
Brown bears are classed as carnivores, and they do eat both small and large animals. Large mammals such as caribou, deer, moose, and muskox can all be taken down by an adult brown bear. However, grizzly bears would rather take down an injured, old, young, or weak individual.
Brown bears will also use their claws to dig ground squirrels and voles from their burrows, especially in the spring after hibernation. Also, around this time, and 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 important in early spring.
Later in the season, brown bears feed on the young calves of caribou, deer, elk, and moose between May and June. Grizzly bears learn the calving grounds of these animals, which stay the same each year, returning to them to feed on the young. Elk makes up a large portion of a brown bear’s diet in these months, with the bears dining consistently upon them.
The diet of the brown bear does depend on their geographical location. The amount of meat that a brown bear eats generally depends on whether the grizzly bears have access to a fish supply.
Brown bears feed on salmon that are spawning, with research indicating that bears with access to the spawning fish consume as much as 75% of meat in their diet. Brown bears with no access to spawning salmon may have a diet with less than 10% meat in their diet.
Although grizzly bears are mostly known for feeding on salmon, they will feed on other fish species, such as trout, when they are available.
During summer, brown bears will feed on the salmon in Alaska and British Columbia who go there to spawn. Only bears in those areas will travel to feed on the spawning salmon.
During July, salmon move through the rivers and lakes of Brooks Falls in Katmai National Park in Alaska. Earlier in the season, the salmon make a feast for the bears as it is one of the first streams that the pre-spawned salmon enter, with Brooks Falls creating a barrier to the salmon.
Brown bears have been seen to eat up to 100 pounds of salmon daily. This can amount to up to 40 salmon a day.
How much of the fish the bear eats depends on the time of the season. At the start of the spawning season, the bears will eat all of the fish. Later on, in the season, they will eat the parts that are most full of fat.
Although brown bears can eat a lot of meat and fish, they also eat plants. The digestive system of a brown bear is unlike ungulates such as deer and moose.
Whereas deer and moose have four-chambered stomachs that break down plant matter with special bacteria and enzymes, brown bears have a single-chambered stomach.
The intestines and digestive tract of the grizzly bear are short. Due to this, brown bears process food quickly. Tender plants can be processed through the system In just over 7 hours. Knowing the limitations of their digestion system, brown bears prefer to eat young, leafy plants rather than mature plants.
Brown bears will eat bulbs, forbs, fungi, grass, and tubers as part of their diet. They will also eat the bulbs, corms, and roots that grow beneath the surface. Whereas black bears do not have long claws, brown bears do, which allow them to dig the plants up with ease. Some plants such as biscuit root and sweetvetch are important plants to provide nutrition to the bears.
Plants make up a large part of the bear’s diet when they wake up from hibernation. In spring, when the bears awake, the plants are beginning to grow. At lower elevations, the snow melts quicker than at higher elevations and then bears use this to their advantage. The bears stay at lower elevations until the snow melts higher up, then move up to feed on the new, softer grasses.
Grizzly bears eat insects as an important part of their diet. Brown bears will eat earthworms, wasp nests, ants, and beetle larvae. Grizzly bears feed on a large diet of moths, especially during the summer months. Grizzly bears can eat up to 40,000 moths in a day, making the moth a key food source.
With each moth containing half a calorie, a bear can consume a huge amount of calories just from moths. Some researchers have advised that a bear can eat six months of calories in a single month, just from 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 under rocks on the mountain slopes in boulder fields.
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 be able to feast on large amounts of these moths. Brown bears are strong animals and can turn over the rocks and boulders with their paws. This allows them to feed on many moths at once.
Whereas grizzly bears do not generally share their territories, they will tolerate each other in closer proximity in these boulder fields where there is a large food source of moths.
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.
Fruit and Nuts
During the late summer, brown bears come down to lower elevations to eat the fresh berries. Chokecherries, huckleberries, raspberries, and rose hips provide extra calories for the bears in these warmer months.
During the fall, bears eat these caloric sugar-laden berries to put on weight before the period of hibernation. In years where there is less food in the wild, bears are more likely to raid human farms looking for the sugary berries.
Brown bears also feed on nuts, with the whitebark pine tree’s nuts being important to them.
The cones have plenty of nuts, especially in grizzly bear areas such as Yellowstone National Park and Grand Teton Nation Park. Although the whitebark tree’s pine nuts grow high up, brown bears are not known for their climbing ability. Instead, they raid the nuts already harvested by the red squirrels.