Brown bear

Where are they located?

In the past, the Ursus arctos was found across a wide area of North America (including northern Mexico), throughout Europe, Asia, the Middle East, and even, in isolated cases, in North Africa.

Currently, the largest number of individuals is found in Russia, with over 100,000. Alaska is home to 31,000, and Canada, 25,000.

There are also several populations in northern and eastern Europe: Romania has about 5,000 and Sweden, 3,500. However, prolonged overexploitation extending back centuries has led to the disappearance of brown bears from a good number of European countries.

In southern Europe, only extremely small and isolated populations can be found, with the following distribution: Greece, 150; Cantabrian Mountains, 200; Abruzzo, 40; Trentino, 50; and the Pyrenees, 30-35.

Populations are also reduced and fragmented in the southern parts of Asia and North America. In the Middle East, they appear to have disappeared from Syria and possibly Bhutan. The date of their disappearance from North Africa is uncertain.

Globally, the population remains numerous and is not significantly declining. There are small and isolated populations that are at risk of disappearing, but others, due to increased protection, are expanding.

What is its habitat?

The brown bear can live in a wide variety of habitats, from dry steppe to ice floes and high mountain forests. They can be found at sea level or at an altitude of 5,000 m or more. However, their preferred habitat is a thick area where they can take shelter during the day.

They are solitary animals, except for mothers with cubs (the only social bonds are formed between females and their young) and during mating season. They may also gather around a food source. They tend to have home ranges rather than strict territories, as they are essentially not territorial.

These ranges can extend up to 4,000 square kilometers, varying according to the availability of food in each habitat. The males' ranges are much larger than the females', and home ranges can overlap.

Are they endangered?

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Brown bear

Did you know...?

Females typically mate with 3 to 4 males during the breeding season, but females have been observed mating with 20 males. Males mate with a range of 1 to 8 females during the breeding season, although many do not manage to mate.

In general, female promiscuity is attributed to infanticide avoidance resulting from paternal confusion, either directly, through male recognition, or indirectly, due to multiple paternity.

The brown bear has been considered an extremely dangerous animal, but the danger of attack in practice is low and exaggerated. In general, they try to avoid human contact and do not attack. They are unpredictable only in their vital space, especially if there are cubs or they are feeding.

Frequently asked questions

How do they recognize each other?

The Ursus arctos is one of the largest living carnivores. However, the size and weight of this bear vary considerably between populations. This is a result of both genetic factors and nutrition.

Brown bears are between 1 and 3 m long, from head to rump, and their shoulder height is between 90 and 150 cm. Their average weight is about 200 kg for males and 135 kg for females. In all populations, males are generally larger and heavier than females. Weight is also an indicator of large seasonal fluctuations.

The heaviest individuals have been found in populations with access to salmon on the coast of Alaska, where some males can weigh up to 780 kg. On the other hand, the smallest are found in southern Europe and Alberta (Canada), where they weigh, on average, between 70 and 55 kg respectively.

The fur is generally brown, but its range goes from cream to black. They molt once a year. Their ears are small and round, they have a pronounced shoulder hump, and their tail is small, almost invisible.

How do they behave?

The Ursus arctos has a slow, clumsy gait, but is capable of reaching speeds of 50-60 km/h. It is primarily terrestrial, but can often be observed swimming or pouncing on fish in the water. Adults may have difficulty climbing trees. They stand on their hind legs to inspect the terrain, intimidate opponents, or reach food.

When are they active?

They are usually active at dusk or at night, and during the day they usually rest (in part, to escape human presence). Only females with cubs are actively diurnal. They take refuge in caves or dig their own dens (usually under protected cover) and rest on beds of dry vegetation. They usually reuse their dens year after year.

From October to December there is a period of inactivity for the brown bear, which is fully active between March and May. Before hibernation, they eat large amounts of food in order to increase their fat layer. The duration of hibernation depends on the location, weather, and condition of each individual. In southern areas, it is very brief or may not even occur.

Hibernation is marked by deep sleep. Heart and breathing rates decrease, and body temperature drops a few degrees. Bears stop eating, drinking, defecating, and urinating. Vital signs are maintained thanks to the energy stored in fat reserves.

How do they mate?

Mating occurs from spring to summer. During estrus, female brown bears copulate with several males, and it is common for them to have two estrus periods per season. Males travel long distances in search of potential mates and also copulate with several females. In general, females control mating.

In female brown bears, ovulation is induced by copulation, which increases the chances of pregnancy. Additionally, implantation is delayed. This means that the fertilized egg remains dormant in the uterus for about 5 months and is not implanted until November-December, when the female begins hibernation.

Seasonal polyestrus, combined with this delayed implantation, explains why multiple paternity often occurs. Cubs are born between January and March, after a gestation period of 6 to 8 months, while the mother hibernates. Each litter consists of 1 to 3 cubs.

Brown bears reach sexual maturity relatively late, between 3.5 and 6 years of age. Their reproductive cycles are very long. Females do not ovulate again until 2.5 to 6 years after their last birth. This varies depending on the survival of the offspring, as well as environmental and geographical conditions.

About your offspring

Cubs are born blind, with only a thin coat of fur and limited mobility. They weigh less than 1% of the mother's weight, which is between 285 and 600g. They must be fed by the mother. Weaning ends when they are between 1.5 and 2.5 years old, although by 5 months of age they already eat a wide variety of foods.

Maternal care continues until they are 3.5 years old. The risk of cub mortality is especially high during the first year. Once the mother leaves them, they usually stay with her for up to 1 more year. Paternal care is absent.

Infanticide is considered the main cause of death for brown bear cubs. Researchers disagree on the reasons for this fact. Some argue that males kill unrelated, dependent offspring to shorten the female's hibernation period. This way, they have a better chance of siring, either by directly mating with females or indirectly, by reducing the number of competing males. Other researchers argue that males have the sole purpose of reducing prospective and immediate competition.

What do they feed on?

Brown bears are omnivores, but they mainly eat plants. They adapt to the diet dictated by the season or geographical area where they are found. During spring, they feed on grass, sedge, bulbs, and moss. In summer and early autumn, they eat berries, acorns, bulbs, and tubers. They eat insects, mushrooms, and roots throughout the year.

The Ursus arctos also feeds on small mammals such as mice, ground squirrels, marmots, and other animals adapted to subterranean life. Additionally, they also eat carrion, if available. In the Rocky Mountains, bears are quite carnivorous and hunt sheep, goats, and elk. In Alaska, moose calves and caribou can also be hunted by them. In Europe, hunting sheep, cattle, horses, and goats is very sporadic, almost exceptional. Along the Pacific coast, brown bears also feed on salmon in the summer.

Do they have predators?

Due to their size and aggressive response to threats, grizzly bears are not usually hunted by other predators. Humans have pursued them throughout recent history, and occasionally, other bears, cougars, or wolves may attack some cubs.

Communication and the Senses

Brown bears have an excellent sense of smell and a human-level sense of hearing, but their eyesight is relatively poor. Therefore, they communicate primarily through smell and sound, which enables them, for example, to follow the scent of a carcass for miles.

Researchers disagree on why brown bears scratch and rub trees. A recent study posits that marking trees may be a means for adult males to familiarize themselves with each other, and that this scent familiarity could play an important role in reducing fights among adult bears.

When angry or scared, they often make noises.

What is its lifespan?

Average life expectancy in the wild: 25-30 years.
Average life expectancy in captivity: 47 years.

What is its global population?

The global population of the Ursus arctos is estimated to exceed 200,000 individuals. The largest populations are found in Russia (over 100,000), Alaska (31,000), and Canada (25,000). There are also large populations in China (7,000), Romania (5,000), Sweden (3,500), and Japan (2,000).