Brown bear

• 1. Introduction

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  Ursus arctos, the brown bear, can weigh up to 600 kg, stand nearly three meters tall, and run down a moose across crusted snow. Yet 90% of what it eats comes from plants. That contradiction sits at the heart of one of the most widely misunderstood animals on Earth. Across Eurasia and North America, brown bears have prowled forests, coastlines, river valleys, and mountain slopes for hundreds of thousands of years, outlasting ice ages, megafauna extinctions, and the expansion of every civilization that has ever shared land with them. How did this species become so adaptable? What does a brown bear's social life actually look like? And what is the uneasy relationship between humans and this bear that has shaped folklore, law, and conservation policy across the entire Northern Hemisphere?

• 2. Ancient Lineage

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  The oldest brown bear fossils found in Asia date from roughly 500,000 to 300,000 years ago, though the lineage stretches back further still. Scientists believe the brown bear evolved from the Etruscan bear, Ursus etruscus, during the early Pliocene epoch in Asia. A genetic analysis placed the divergence of the brown bear lineage from the cave bear species-complex at approximately 1.2 to 1.4 million years ago. Brown bears entered Europe around 250,000 years ago and North Africa shortly after that.

  Reaching North America required crossing the ancient land bridge of Beringia, and brown bears made that crossing during the Illinoian Glaciation. The founding population of most North American brown bears arrived first, with the genetic lineage developing around 177,000 years before present. A local extinction in Beringia approximately 33,000 years ago was followed by two new, closely related lineages that repopulated Alaska and northern Canada from Eurasia after the Last Glacial Maximum.

  Carl Linnaeus formally described the species under the name Ursus arctos in the 1758 edition of his Systema Naturae. Decades of subsequent taxonomy have been described as "formidable and confusing"; as many as 90 subspecies have been proposed, and few authorities agree on the same list. A 2008 DNA analysis identified as few as five main clades covering all extant brown bears, while a 2017 phylogenetic study found nine clades, including one representing polar bears. The bears of the Alexander Archipelago carry an unusual legacy: island populations there hold polar bear DNA, presumably from polar bears stranded at the end of the Pleistocene, yet their nuclear genomes show more than 90% brown bear ancestry.

• 3. Built to Dig and Eat

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  Brown bears are sexually dimorphic, with adult males averaging at least 30% larger than females. Their paws reach 21 cm wide and 36 cm long, and their front claws can measure 7 to 10 cm along the curve. The shoulder hump, unique among bears, is composed entirely of muscle and evolved specifically to generate force for digging. No other living bear species has it.

  Their skull is massive and concave, with well-developed projections and strong jaws. Skull lengths in Russian brown bears range from 31.5 to 45.5 cm for males and 27.5 to 39.7 cm for females. The first three molars of both the upper and lower jaw are underdeveloped, and certain molars are frequently lost early in life. The resulting dental arrangement reflects a diet built for flexibility rather than specialization.

  Fur color varies far more than the species name implies. In India, brown bears can be reddish with silver-tipped hairs. In China, some bears have a yellowish-brown or whitish collar across the neck, chest, and shoulders. North American grizzlies run from nearly black to cream. The winter coat in northern subspecies can reach 11 to 12 cm at the withers; the summer coat is much shorter and sparser. The name "grizzly" itself comes from the characteristic coloration of hairs that are brownish-black at the base and whitish-cream at the tips.

• 4. The Omnivore's Playbook

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  Bears in Yellowstone National Park have been recorded consuming as many as 40,000 army cutworm moths in a single day, deriving up to half of their annual food energy from those insects alone. That number captures something essential about how a brown bear feeds: opportunistically, seasonally, and at enormous scale.

  Plant matter dominates the diet across the year. In spring, the staples are winter-killed carrion, grasses, shoots, sedges, moss, and forbs. Berries and other fruits become critical through summer and early autumn. Roots and bulbs serve as fallback calories when fruit crops fail. Brown bears use their long, strong claws to tear through soil and their powerful jaws to bite through tough roots, a foraging style no other bear matches.

  Coastal populations show a markedly different seasonal rhythm. In the Kamchatka peninsula and parts of Alaska, bears feed primarily on spawning salmon. They congregate near falls where the fish are forced to leap, catching them mid-air or pinning them in shallow water with their claws. At the peak of a salmon run, when fish are plentiful, bears may eat only the eggs and head of each fish, leaving the rest to red foxes, bald eagles, common ravens, and gulls. Salmon abundance explains the exceptional size of coastal bears, whose adults weigh roughly twice as much as inland bears.

  Predation of large mammals is less common than popularly believed. Many bears charge large prey and give up; the prey escapes alive. Bears that do pursue ungulates, such as elk, moose, caribou, muskoxen, or wild boar, typically learned the skill from their mothers. They usually target young or infirm animals, and they kill by brute force rather than the specialized methods of wolves or big cats. On rare occasions, a bear striking with its forelimbs has broken the neck or back of an adult moose or adult bison.

• 5. Social Life and Reproduction

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  A 2014 study found that brown bears peak in activity during the morning and early evening hours, though bears living near humans tend to shift toward fully nocturnal schedules. For most of the year the species is solitary, but that solitude is not absolute. Bears gather at concentrated food sources and form hierarchies based on age and size. Adult males are particularly aggressive. Females with cubs rival adult males in aggression and are less tolerant of other bears than solitary females.

  Dominance is displayed through posture: a frontal orientation with canine teeth visible, muzzle twisting, and neck stretching. A subordinate responds by turning away, dropping the head, and sitting or lying down. Brown bears also rely on sound: huffing signals tension, woofing signals alarm, growling and roaring accompany aggression. A rumbling growl can escalate to a roar during a charge, and that roar has been described as "thunderous," capable of traveling 2 km.

  The mating season runs from mid-May to early July. Females mature sexually between four and eight years of age. Through delayed implantation, a fertilized egg divides and floats freely in the uterus for six months before attaching to the uterine wall during winter dormancy; the cubs are born roughly eight weeks later. Litters typically contain one to three cubs, though as many as six have been recorded. At birth, cubs are blind, toothless, and hairless, weighing 350 to 510 grams.

  Cubs remain with their mother for an average of 2.5 years in North America, during which they learn by imitation rather than instinct: which foods are most nutritious, how to hunt and fish, and where to den. Brain size in large carnivores has been positively linked to whether the species raises offspring solitarily, and the relatively large brain of a female brown bear is considered key to that teaching role. Infanticide by adult males does occur; a male that kills another's cubs can bring the female back into oestrus within two to four days.

• 6. Rivals and Predators

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  Following a decline in ungulate populations between 1944 and 1959 in the Russian Far East, researchers documented 32 cases of Siberian tigers attacking Ussuri brown bears. Ussuri brown bears and smaller black bears together make up 2.1% of the Siberian tiger's annual diet, with brown bears accounting for 1.4%. A study carried out between 1993 and 2002 found no cases of tigers preying on denned bears, suggesting tigers typically target bears that are active.

  With wolves, the relationship is more one of competition than predation. In Yellowstone National Park, Doug Smith, director of the Yellowstone Wolf Project, wrote that the arrival of bears after a wolf kill is a question of when, not if. Despite frequent clashes over carcasses, most encounters end without injury to either side. As of the time of writing, there is a single recorded case of fully-grown wolves being killed by a grizzly bear.

  Among bear species, brown bears generally dominate where ranges overlap. American black bears, smaller and suited to forested terrain, yield ground to grizzlies in open areas. Climate change appears to be driving increasing contact between brown bears and polar bears; brown and grizzly bears have been recorded moving northward into territory previously held by polar bears, and dead polar bear cubs have been found in brown bear dens. The first wild grizzly-polar bear hybrid was confirmed in 2006, when DNA testing of a bear shot in the Canadian Arctic revealed the crossbreeding. By the time of that confirmation, seven more hybrids had been identified in the same region, all descended from a single female polar bear.

• 7. Range, Numbers, and Conservation

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  Approximately 200,000 brown bears remain in the world. Russia holds the largest share, with around 130,000. The United States follows with approximately 32,500, and Canada holds around 25,000. Alaska alone accounts for an estimated 30,000 bears, a population considered healthy.

  In Europe, around 14,000 bears were counted across ten fragmented populations as of 2010. Romania held 5,000 to 6,000. In the Pyrenees, shared between Spain, France, and Andorra, the estimate stood at just 20 to 25 animals that same year. The Marsican brown bear of central Italy is isolated to the point of critical fragility, with a population of roughly 50 bears. The Himalayan brown bear occupies only 2% of its former range and faces uncontrolled poaching for its body parts.

  The brown bear and the American black bear are the only bear species not classified as threatened by the IUCN, yet regional losses have been severe. The Atlas bear of North Africa, the California grizzly, the Ungavan population, and the Mexican grizzly were all hunted to extinction in the 19th and 20th centuries. A European action plan published in 2000 addressed the conflict between bears and farmers by compensating people for losses of livestock, food supplies, and shelter, while also funding preservation and expansion of forest habitat. In Sweden, bears increased at a rate of 1.5% per annum between the 1940s and 1990s under that kind of managed approach.

  Poaching remains a serious ongoing threat. A three-year survey in the Russian Far East detected the illegal shipment of brown bear gallbladders to Southeast Asian countries. Roads and railway tracks also pose a mortality risk, and agricultural land use has reduced habitat across much of the southern range. In Himalayan Nepal, farmers have killed brown bears in retaliation for livestock predation, a dynamic that conservation efforts continue to navigate.

• 8. Bears in Human Culture

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  The earliest cave paintings of bears date to the Paleolithic, with over 100 recorded images. That visual record is a starting point for a relationship between humans and brown bears that runs through nearly every culture that ever shared a landscape with them.

  In Japanese history, the bear nicknamed Kesagake killed seven people and wounded three others during a series of attacks in Tomamae, Hokkaido, in December 1915 before being killed in a large-scale hunt. That event stands as the worst brown bear attack in Japanese recorded history. A 2019 study covering a 15-year period from 2000 to 2015 counted 664 bear attacks across North America and Eurasia, resulting in 568 injuries and 95 fatalities. Around 10 people a year are killed by brown bears in Russia alone, more than in all other parts of the bear's range combined.

  Cultural weight runs the other direction as well. The brown bear is Finland's national animal. The grizzly bear is the state animal of Montana. California still designates the California golden bear as its state animal, despite the animal's extinction. The coat of arms of Madrid shows a bear reaching into a madroño tree for fruit. The Swiss city of Bern's coat of arms depicts a bear, and the city's name is widely thought to derive from the German word for the animal. The Croatian 5-kuna coin, minted since 1993, carries the brown bear on its reverse.

  Native American cultures across North America accorded bears spiritual significance. The Denaa people severed all four paws of a slain bear to prevent its spirit from escaping. Community members who wore bear claw necklaces were regarded as brave, and the clattering of those necklaces was believed to carry therapeutic power. In Haida tradition, one legend holds that a marriage between a woman and a grizzly bear founded the lineage of the native people, a story understood as explaining why the Haida could live alongside bears.

  In European children's literature, brown bears appear in "Goldilocks and the Three Bears" from England, "Snow White and Rose Red" in German-speaking countries, and the widely read American book Brown Bear, Brown Bear, What Do You See? The longest-lived brown bear on record, a male named Andreas kept at the Arcturos bear sanctuary in northern Greece, was at least 50 years old when he died in 2013.