On a rocky mountain slope in midsummer, a grizzly flips a boulder and licks up the moths hiding underneath. Hundreds of kilometres away, another grizzly stands in a waterfall, waiting for a salmon to leap. Same species, very different menus, and both sit at the top of their food chains.
A grizzly bear is an omnivore near the top of its food chain. It eats plants, roots, berries, nuts, insects, fish and mammals such as elk calves, and it scavenges carcasses. Adult grizzlies have almost no natural predators except other bears and people. In Yellowstone alone, scientists have recorded grizzlies eating more than 266 species (National Park Service).
Key takeaways
- Position: top consumer (apex omnivore); adults are rarely killed by anything but other bears and humans.
- Diet breadth: more than 266 species in Yellowstone, including 162+ plants, 26+ mammals and 36+ invertebrates.
- Richest food: army cutworm moths, at 7.9 kcal per gram, more than elk meat.
- Ecosystem link: coastal bears carry salmon into forests; up to about 18% of the nitrogen in nearby spruce needles came from salmon in one Alaska study.
What does the grizzly bear food chain look like?
A simple grizzly food chain starts with plants such as grasses, berries and whitebark pine. Plant-eaters such as elk, ground squirrels and moths eat those plants. The grizzly eats both the plants and the plant-eaters, so it feeds at several levels at once. Click any animal with an underline to read its own Zooologist article.
Picture it: the grizzly food web
Arrows point from food to eater. Linked names open the full article.
Army cutworm moths
Ants
Cutthroat trout
Salmon
Grasses and sedges · roots · berries · whitebark pine nuts · flowering plants
Energy from the Sun
Based on NPS, USFWS and Alaska Department of Fish and Game sources listed below. Grizzlies also eat the plants directly, so arrows really run from every level to the bear.
What do grizzly bears eat?
Grizzlies are opportunistic omnivores. A 2015 review of Yellowstone research found they eat more than 266 species: over 162 plants, seven mushrooms, at least 26 mammals, 4 fish, 3 birds, 1 amphibian and at least 36 invertebrates, including 24 kinds of ant (NPS). In Alaska, brown bears eat salmon, berries, grasses, sedges, roots, ground squirrels and carrion, and prey on moose and caribou, especially newborns (Alaska Department of Fish and Game).
For the season-by-season menu, read what grizzly bears eat, or the wider brown bear diet.
Which grizzly foods give the most energy?
Not the ones you might expect. Army cutworm moths provide about 7.9 kilocalories per gram, the highest of any grizzly food measured. Ungulate meat such as elk gives 6.8, trout 6.1, berries 3.2 and grasses only 2.5 (NPS). A bear licking moths off rocks can be eating richer food than one chewing an elk.
Picture it: energy per gram
Army cutworm moths: 7.9 kcal/g
Elk and other hoofed animals: 6.8
Trout: 6.1
Berries: 3.2
Grasses and sedges: 2.5
Source: NPS, Yellowstone Science (2015).
How does the grizzly’s food chain change through the year?
In Yellowstone, spring bears rely on elk and bison, mostly as winter-killed and wolf-killed carcasses, plus hunting elk calves until about mid-July. Summer brings moths, ants and spawning cutthroat trout. In autumn, whitebark pine nuts are the most important food in years with a good seed crop, sometimes dug from red squirrel stores (NPS).
This flexibility matters because foods come and go. Whitebark pine does not produce a big seed crop every year, so bears switch foods when one fails.
What eats grizzly bears?
Very little. Adult grizzlies are too big for most predators; see how much a grizzly weighs. Alaska Department of Fish and Game lists other brown bears as the predator of cubs (ADF&G). People have been the biggest threat: about 50,000 grizzlies lived in the western lower 48 US states before 1800, falling to 700–800 by 1975 (USFWS).
Grizzlies and wolves compete for the same carcasses. In Yellowstone, grizzlies often take wolf-killed carcasses from wolf packs through the summer (NPS). Read how strong a grizzly is.
How do grizzly bears help forests grow?
Coastal brown bears move ocean nutrients onto land. In a study on Alaska’s Kenai Peninsula, Hilderbrand and colleagues estimated that 15.5–17.8% of the nitrogen in white spruce needles within 500 m of a salmon stream came from salmon, and bears delivered 83–84% of it, mostly through their urine (Hilderbrand et al. 1999).
So a bear eating a salmon is part of a chain that runs from the ocean to the treetops. Bears also spread seeds from the berries they eat. If grizzlies disappear, predators of elk calves are fewer, and less salmon nitrogen reaches streamside forests.
How do threats to the food chain affect grizzlies?
When a key food declines, grizzlies feel it. Whitebark pine trees across the Greater Yellowstone have died in large numbers since the early 2000s, and cutthroat trout are estimated at less than 10% of their historical numbers (NPS). Bears have adapted by switching foods, but human food and garbage can draw them into conflict.
In the lower 48 US states, grizzlies are listed as Threatened, with at least 1,923 bears, including about 727 in the Greater Yellowstone area (USFWS). See where grizzly bears live.
Three things you can do: in bear country, store food and rubbish in bear-proof containers; carry bear spray and make noise on trails; and support groups protecting whitebark pine and salmon rivers.
Myths about the grizzly food chain
Myth: Grizzlies are pure meat-eaters.
Fact: More than 162 of the 266-plus species they eat in Yellowstone are plants (NPS).
Myth: Grizzlies kill most of the meat they eat.
Fact: In spring, much of it is carrion from winter-killed or wolf-killed animals (NPS).
Myth: Insects are too small to matter to a bear.
Fact: Moths are their richest food, and ants appear in every Yellowstone grizzly diet study from 1943 to 2009 (NPS).
Test yourself
1. Which grizzly food has the most energy per gram?
Army cutworm moths, at about 7.9 kcal/g.
2. Name one way grizzlies get meat without hunting.
Scavenging carcasses, including winter-killed animals and wolf kills.
3. How do bears move nitrogen from the sea into forests?
They eat salmon and leave nitrogen in the forest, mainly through urine.
Where to next?
➡️ Go wider: where grizzly bears live⬆️ Go deeper: grizzly bear adaptations🔀 Go sideways: grizzly-polar bear hybrids
Frequently asked questions
Is a grizzly bear a producer, consumer or decomposer?
A consumer. Because it eats both plants and animals, it is an omnivore that feeds at several levels of the food chain. It is a primary consumer when eating berries and a higher-level consumer when eating elk calves or fish.
Is the grizzly bear an apex predator?
Yes, in most places. Adult grizzlies have no regular natural predators. Other brown bears kill cubs, and people have historically caused most grizzly deaths through hunting, trapping and conflict.
Do grizzlies and wolves compete?
Yes. In Yellowstone, grizzlies regularly take over carcasses killed by wolf packs, especially in spring and summer, according to the National Park Service.
Sources
- National Park Service, Yellowstone Science (2015). Grizzly bears: ultimate omnivores of the Greater Yellowstone Ecosystem.
- National Park Service. Food habits of bears in the Yellowstone ecosystem.
- National Park Service. Response of grizzly bears to changing food resources.
- Alaska Department of Fish and Game. Brown bear species profile.
- US Fish and Wildlife Service. Grizzly bear.
- Hilderbrand, G.V., Hanley, T.A., Robbins, C.T. and Schwartz, C.C. (1999). Role of brown bears (Ursus arctos) in the flow of marine nitrogen into a terrestrial ecosystem. Oecologia 121: 546-550.
Sources checked 12 October 2026.
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