Bears are enthusiastic scavengers, and few animals in North American woods are better equipped to find and claim a dead animal. For most bears, though, meat is a side dish rather than the main course, and scavenging rises and falls with the seasons. The habit has a practical side for people: a bear feeding on or guarding a carcass is among the most dangerous bears you can meet.1Interagency Grizzly Bear Committee. Encounter Behavior & Myths (Be Bear Aware)
How Much of a Bear’s Diet Is Dead Animals
Bears belong to the carnivore group of mammals, but they eat far more plants than meat.2Florida Fish And Wildlife Conservation Commission. myths A Florida black bear’s diet is about 80% plants like leaves, nuts and berries, 15% insects and 5% meat such as carrion, opossum and armadillo.3Florida Fish And Wildlife Conservation Commission. myths Carrion simply means animals that were already dead when the bear found them.
Brown and grizzly bears eat more meat, and much of it is found dead. Grizzlies eat fruit, nuts, roots and seaweed alongside insects, rodents, fish and carrion.4Better Planet Education. Bear (Grizzly) – Food and Hunting Over 100 mammal species have turned up in brown bear diets, though much of that was probably scavenged.5Wikipedia. Dietary biology of the brown bear In most of their range brown bears regularly eat hoofed animals like deer and elk, often as carrion.6Wikipedia. Dietary biology of the brown bear The balance varies by place: in Slovenia this meat was four times more likely scavenged than hunted, while in east-central Alaska live hunting was four times more common.7Wikipedia. Dietary biology of the brown bear
A mostly plant-eating animal still seeks out carcasses because the payoff is so large. Bears digest plants much less efficiently than true plant-eaters like cows, so they gain more from dense, protein-rich food. A big carcass delivers fat and protein that berries and grasses can’t match without hours of foraging. It also carries no risk of injury the way chasing or fighting healthy prey does, which matters because a hurt bear may not survive the next winter.
Diet percentages are also averages over a year and across many bears, so one bear in one month may eat far more or far less meat. Researchers estimate diets from scat, stomach contents, and chemical signatures in hair or bone, and these methods can’t always tell hunted meat from scavenged. Hoofed-animal remains in scat could come from a kill or a carcass, hence the “probably scavenged.”
Spring Is Scavenging Season
In spring, carcasses left from winter, plus grasses, shoots and sedges, are staple foods for brown bears almost everywhere they live.8Wikipedia. Dietary biology of the brown bear Deep snow, ice, avalanches and starvation kill many deer, elk and other hoofed animals over winter, and the thaw exposes them.9Wikipedia. Dietary biology of the brown bear In Yellowstone, grizzlies in spring search out winter-killed elk and bison, along with dandelions, grasses and even roots stored by pocket gophers.10Teton Science Schools. Yellowstone’s Bears in Spring
A thawing carcass matters so much because bears live off stored body fat during winter dormancy and emerge lighter and hungry. Early spring plants are young, watery and low in calories, so grazing alone gains little at first. A winter-killed animal offers a large, concentrated meal at the moment the bear’s needs are greatest. Females that come out with newborn cubs are nursing on depleted reserves, so a rich carcass is especially valuable to them.
For people, this means early-season hikers and anglers may reach places where melting snow is exposing animals that died over winter. Avalanche runouts and valley bottoms tend to collect winter kills, so a hungry bear may visit them repeatedly. A strong smell of decay, circling ravens, or a carcass seen ahead are reasons to turn around and take another route rather than go closer. In terrain like this, making noise and keeping bear spray within reach is sensible, since a hungry bear may be guarding its find.
How Bears Find Dead Animals
The scent-detecting lining inside a black bear’s nose has about 100 times the area of a human’s.11nps.gov. Bear Series, Part One: A Bear A black bear’s sense of smell is estimated at about seven times better than a bloodhound’s.12nps.gov. Bear Series, Part One: A Bear Bears’ larger, folded nasal passages pack in more scent receptors and catch more scent molecules from each breath.13Lions Tigers and Bears. Bears and Their Keen Sense of Smell The brain area that processes smell is large too, about five times the size of a human’s.14BearVault. How Well Can Bears Smell? Grizzlies can reportedly detect carrion from as far as 28 km away.15Better Planet Education. Bear (Grizzly) – Food and Hunting
A bear sniffing the air picks up scent molecules carried on the wind. It often moves upwind or zigzags across the scent trail, tracking the odor back to a source that may be miles off. Decay releases strong-smelling gases, so a carcass becomes easier to detect as it rots. Because the smell fades with distance, a bear may lose and regain the trail as wind shifts or terrain channels the air.
Any meat, fish or food smell can pull a bear in the same way. Storing food sealed and away from tents reduces the pull, and cleaning game away from camp keeps the scent elsewhere.
Why Bears Bury and Guard Carcasses
Grizzlies often bury large carcasses like elk, moose or bison under leaves, dirt, branches or snow.16A-Z Animals. These Animals Hide Dead Bodies to Eat Them Later A big animal takes several days to eat, and covering it keeps the meat cool and slows rot.17A-Z Animals. These Animals Hide Dead Bodies to Eat Them Later It also hides the meal from wolves, coyotes, ravens and other bears.18A-Z Animals. These Animals Hide Dead Bodies to Eat Them Later Black bears cache too: one Asiatic black bear covered a carcass with leaves within 16 minutes of finding it and was still covering it with needles months later.19Ursus. Food caching by bears: a literature review and new observations for Asiatic and American black bears
To spot a cache, look for a mound of soil, leaves, sticks or moss that seems out of place on the forest floor, often roughly the size of the animal underneath. Scraped or torn-up ground and uprooted plants nearby are common because the bear gathers cover material from around the pile. A strong smell of rot may come from it, though a cold or recent cache may smell weaker. Ravens or other scavenging birds gathering in one spot may point to it, but their absence doesn’t mean the site is safe.
Most dangerous bear encounters happen when a bear is surprised, protecting cubs, or guarding a large food source like a carcass.20Interagency Grizzly Bear Committee. Encounter Behavior & Myths (Be Bear Aware) So a mound of dirt and branches with a dead-animal smell may mean a bear is nearby and will defend it. If you find one, back away the way you came and leave the area rather than investigating.
Hunters’ Leftovers and Other Human Sources
Hunters often leave a gut pile, the entrails removed when field-dressing an animal, and grizzlies are known to target these.21The Journal of Wildlife Management. Lead exposure in large carnivores in the greater Yellowstone ecosystem Cameras on moose gut piles caught black bears, coyotes and eagles feeding, with ravens the most frequent visitors.22PubMed Central. High Risk of Lead Contamination for Scavengers in an Area with High Moose Hunting Success Gut piles from animals shot with lead bullets can also expose bears to lead.23The Journal of Wildlife Management. Lead exposure in large carnivores in the greater Yellowstone ecosystem
For hunters, a few habits lower the risk. Pack meat out as soon as you can rather than leaving it overnight, since a carcass left in the field can draw a bear within hours. If you must return to a kill, approach slowly, watch for signs like a covered pile or ravens, and make noise so you don’t surprise a bear. When meat has to be stored in the field, keep it well away from camp and from the leftover entrails, hung where possible, so a bear drawn to it isn’t near where you sleep. Non-lead ammunition removes the lead risk for bears and other animals that feed on gut piles.
Human-made carrion extends beyond hunting. Dead animals along roads can draw bears near traffic, and dumped carcasses or livestock remains near homes can teach bears to come close. Reporting carcasses lets agencies remove them.
Competition at a Carcass
Where bears are present, they can be the main animals feeding on carcasses, and coyotes, dogs and magpies feed far less.24PubMed Central. The taphonomic impact of scavenger guilds in peri-urban and rural regions of central and southern Alberta. Part II – Dispersal patterns of forensically relevant vertebrate scavengers In Yellowstone, wolves, grizzlies and black bears steal kills from cougars.25UW-National Park Service Research Station Annual Reports. Effects of wolf and grizzly bear recovery on cougars in the Southern Greater Yellowstone Ecosystem Scientists think ancient giant bears grew large partly so they could take over carcasses killed by other predators.26Biology Letters. Giant prehistoric bears evolved to fill scavenger gap
A steal like this often starts when a bear picks up the scent of a fresh cougar or wolf kill and follows it in, sometimes within hours. Its size lets it drive off the hunter, which often retreats rather than risk injury. The predator loses the meal it worked for and must hunt again, spending more energy to replace it.
Among bears, size rules. They follow a pecking order based on age, size and temperament, with mature males at the top and young bears and cubs at the bottom.27Get Bear Smart. Behaviour — Get Bear Smart Big males usually get first claim to a carcass, and younger bears may avoid sites where they are feeding.
Black bears also commonly eat dead bears, a habit that can spread the Trichinella parasite, which can also infect people.28PubMed. Parasites of black bears of the Lake Superior region The parasite risk is one reason people should cook bear meat thoroughly.
Coastal Bears and Washed-Up Carcasses
Polar bears stuck ashore can’t find enough food on land to replace sea-ice hunting.29Journal of Mammalogy. Polar bear–grizzly bear interactions during the autumn open-water period in Alaska Marine mammal carcasses, where available, can help them get through longer stretches on land.30Journal of Mammalogy. Polar bear–grizzly bear interactions during the autumn open-water period in Alaska Along Alaska’s Beaufort Sea coast, bowhead whale remains from local hunts are available every year to bears that come ashore.31Journal of Mammalogy. Polar bear–grizzly bear interactions during the autumn open-water period in Alaska One whale can feed many bears for weeks, and polar and grizzly bears may share coastlines in autumn, so communities near these sites need extra caution.
Bears often carry salmon a short way into the woods to eat.32Grizzly bear conservation and protection. Grizzly Ecology Pt. 3: Bears, Fish, and Trees Decaying salmon can supply up to 24% of the soil’s nitrogen near streams.33Grizzly bear conservation and protection. Grizzly Ecology Pt. 3: Bears, Fish, and Trees Sitka spruce near such streams grew three times faster in one study.34Grizzly bear conservation and protection. Grizzly Ecology Pt. 3: Bears, Fish, and Trees