The Grizzly Bear's Diet: An Omnivore Built for Opportunity
Grizzly bears (Ursus arctos horribilis) are among the most iconic large mammals in North America, and their diet is as impressive as their size. Despite a reputation as fearsome predators, grizzlies get the majority of their calories from plant-based foods. Understanding what grizzlies eat reveals how these animals are perfectly adapted to their environments.
The Breakdown: What Grizzlies Actually Eat
Grizzly bears are opportunistic omnivores, meaning they'll eat almost anything nutritious available to them. Their diet typically breaks down as follows:
- Plants (grasses, sedges, roots, bulbs): A staple in spring when protein-rich food is scarce
- Berries and fruits: Huckleberries, serviceberries, buffaloberries, and chokecherries dominate late summer feeding
- Insects and larvae: Army cutworm moths, ants, and grubs provide critical fat and protein
- Fish: Particularly Pacific salmon during spawning runs — a high-calorie bonanza
- Mammals: Ground squirrels, elk calves, deer fawns, and occasionally adult ungulates
- Carrion: Scavenged carcasses from winter-killed elk or wolf kills
- Honey and bee larvae: When hives are accessible
Salmon: The Ultimate Grizzly Superfood
Perhaps no image is more associated with grizzly bears than one standing in a rushing river, swiping salmon from the water. Salmon fishing is critically important — a single sockeye or chinook salmon can contain thousands of calories. Grizzlies along the Alaska coast and in the Pacific Northwest can gain pounds per day during salmon season, building the fat reserves needed to survive winter.
Bears develop sophisticated fishing strategies: some stand at waterfalls and snatch leaping fish mid-air, others wade in shallow water and pin fish with their paws, and some simply dive face-first. Dominant males often claim the best fishing spots, displacing younger or smaller bears.
Hyperphagia: Eating to Survive Winter
In late summer and fall, grizzlies enter a state called hyperphagia — a period of compulsive, near-constant eating. During this phase, a grizzly may consume up to 20,000 calories per day. They need to gain 30–40% of their body weight in fat before entering their winter den. Failing to do so can be fatal, especially for pregnant females.
How Grizzly Diet Varies by Region
| Region | Primary Food Sources |
|---|---|
| Yellowstone / Rockies | Whitebark pine nuts, cutthroat trout, elk, army cutworm moths |
| Alaska Coast | Salmon, sedges, berries, clams |
| Canadian Rockies | Buffaloberries, ground squirrels, roots, carrion |
| Interior Alaska | Berries, roots, small mammals, fish (seasonal) |
Why Diet Matters for Grizzly Conservation
Grizzly bear populations are directly tied to food availability. The decline of whitebark pine trees — a critical fall food source in Yellowstone — due to climate change and pine beetle infestations has forced bears to seek alternative foods, sometimes bringing them into conflict with humans. Healthy, diverse food ecosystems are essential for grizzly survival.
Key Takeaways
- Grizzlies are omnivores that eat mostly plants, berries, and insects
- Salmon is one of their most important seasonal calorie sources
- They enter hyperphagia in fall to build fat for winter dormancy
- Diet varies significantly based on region and habitat
- Food availability directly influences grizzly population health