BROWN BEAR: CHARACTERISTICS, HABITAT, REPRODUCTION, BEHAVIOR - BIOLOGY - 2025

The brown bear (Ursus arctos) is a placental mammal that is part of the Ursidae family. The coloration of the hairs on the back is dark brown, almost black. However, this may vary depending on the region where you live. Thus, in India the coat is reddish with some silver tones.

It is native to the northeast region of North America, in addition to Asia and Europe. The preferred habitat is wet meadows, tundras, and low elevation riparian areas. One characteristic that identifies it is its claws. These are curved and large, especially on the front legs. The brown bear, as it is also known, uses them to excavate the earth and reach the roots to eat them thanks to its powerful jaws.

Grizzly. Source: Malene Thyssen

The vast majority of the time, this mammal digs its own burrow and makes a bed out of dry vegetation. This is generally located on a slope, either between the roots of a large tree or under a huge stone. This shelter can be reused year after year.

Ursus arctos is omnivorous and feeds on salmon, trout, ungulates, elk, fruits, ants, birds, berries, and carrion.

Period of inactivity

The brown bear begins a period of inactivity in the month of October until December. The exact period in which it occurs is influenced by the climate, the location and the organic condition of the animal.

In southern regions, this phase may not occur and if it does, its duration is very short. During this stage, the bear enters a deep sleep, in which the temperature of the animal's body drops a few degrees.

Some specialists state that it is not a true hibernation, but an inactive period, since bears can easily wake up from the sleep in which they are.

Evolution

The Ursidae family originated in Europe, in the early Miocene, about 20 million years ago. The predecessor is Ursavus elemensis, an extinct species that was similar in size to a dog, although it had characteristics of bears such as teeth. Later they underwent adaptations, such as the reduction of the carnassials and the expansion of the biting surface of the molars.

From Ursus elemensis, firstly, the giant panda is derived and later the spectacled bear. Then there was a polytypic divergence in several species, among which is the Ursus arctos.

According to research, the brown bear evolved from Ursus savinis, which inhabited Asia 800,000 years ago. Ursus arctos reached Europe approximately 250,000 years ago and shortly thereafter north of the African continent.

The species entered Alaska 100,000 years ago, although they did not migrate south until 13,000 years ago. Specialists believe that the movement to the south occurred at the time when the short-nosed bear (Arctodus simus) became extinct.

characteristics

Fur

The brown bear's fur is thick and long, with a long mane located at the back of the neck. This can have variations in each of the species.

During the winter, it is long and thick, and can be between 11 and 12 centimeters long. Also, it is thin and very rough to the touch. In the summer, the hair is scarce and much shorter, aspects that vary according to the geography where you live.

Coloration

Despite being known as brown bears, these animals are not completely brown. The tones may vary according to the habitat where it is found.

Thus, in China, they have a whitish or yellowish stripe around the neck and shoulders, while in India they are reddish, with spiky hairs in silver tones.

Even within the subspecies, various shades of brown can occur. For example, those that live in North America can have a wide range of colors, ranging from a coat so dark brown that it appears black, to a cream or yellowish brown hue.

Legs

The legs are generally large and dark in color, with the end lighter. The rear ones are 21 to 36 centimeters in length, while the front ones can be up to 40% smaller. The width of this limb is around 17.5 to 20 centimeters.

Claws

The claws of Ursus arctos are curved and large, with those on the front legs much longer than the back ones. The length is between 5 and 6 centimeters, and can reach up to 10 centimeters, if the length of the curve is considered.

Due to this particular structure of the claws, added to its excessive weight, when this animal is in the adult stage it is very difficult for them to climb the trees.

Locomotion

The brown bear is a plantigrade animal, which tends to use running walks more frequently than trotting. While walking, this mammal moves at a slow or moderate speed.

According to research carried out, where the factors involved in these movements were evaluated, the reaction force on the ground was more pronounced in the hind legs. Likewise, the speed of force development is notably higher for the hind limbs than for the front ones.

Body

The brown bear, as this species is also known, is the only one within the genus Ursus that has a kind of hump on the upper part of the shoulder. This is a muscle type training.

This characteristic is an adaptation that allows it to have more strength while digging, a typical activity during foraging. Also, thanks to its strong muscles, it can mobilize large amounts of earth that it makes to build its resting place.

Skull

The adult species has a large skull in comparison to its body. Its shape is concave and the forehead area is wide, raised abruptly. As for the base of the brain, it is long and small.

There are geographic variations in the dimensions and characteristics of this bone structure. For example, North American brown bears have flatter profiles than coastal and European ones.

Teeth

Reproduction

The female sexually matures between four and eight years of age, while the male usually between five and nine years. This one needs to be big and strong enough to compete with other males for the right to mate.

The males have large territories, which makes it very difficult for them to detect their possible mates. This is why when the female is ready to have a mate, she excretes a scent that the male can pick up from a distance.

Males will do their best to mate with as many females as they can. Ursus arctos can be with the same pair from a few days before mating to two weeks after.

Outside of that time, females and males do not show any sexual interest between them.

Fertilization

Once the egg is fertilized it does not implant immediately, as it does in many mammals. Females of this species have a delay in implantation, so the fertilized ovum does not attach to the uterus for development until some time before the period of inactivity.

If the female is not well nourished during her hibernation, she could spontaneously expel the fertilized egg. Prolactin, a hormone related to the gestation process, is controlled by photoperiod. This chemical has a great influence on the reactivation of the corpus luteum.

When the egg has already attached itself to the walls of the uterus, the gestation period lasts for 6 to 8 weeks. After this, between one and three cubs are born.

Feeding

The brown bear is omnivorous and eats a wide variety of foods. The diet varies throughout the geography and also depends on the seasons.

For example, during the spring, the bases of their diet are shoots, grasses and sedges. In the fall and summer, berries and fruits become important.

In terms of dietary variability, in Yellowstone National Park, in the western United States, meat consumption accounts for almost 51% of food. In contrast, in Glacier National Park to the north, the intake of animals was only about 11%.

With reference to such diversity, in some interior regions of North America, the diet of Ursus arctos is between 80 and 90% plant-based.

Plants

As for the plant material it eats, there are mountain ash (Sorbus sitchensis), hawthorn (Crataegus spp.), Blueberry (Symphoricarpos spp.), Honeysuckle (Lonicera spp.), Pine (Pinaceae) and willow (Salix spp..).

Besides these there is also the dandelion (Taraxacum spp.), Blueberry (Vaccinium spp.), Clover (Trifolium spp.), Grass (Heracleum spp.), Horsetail (Equisetum spp.), Strawberry (Fragaria spp.) and thistle (Cirsium spp.).

Invertebrates

To obtain the beetles, worms and insects, the brown bear searches for nests, although it could also dig in the ground. In Eurasia, wasps and honey bees are consumed to a high degree.

Other insects that form their diet are ants and ladybug beetles. Those who live along the beaches, dig for clams and crabs.

Fishes

Brown bears feed primarily on trout, belonging to the genus Oncorhynchus. They also eat pink salmon (O. gorbuscha) and sockeye salmon (O. nerka).

Likewise, in Canada they hunt broad whitefish Coregonus nasus and Catostomus catostomus. In Siberia, they prefer the northern pike (Esox lucius) and grayling (Thymallus thymallus).

Mammals

In addition to predation by salmon, the vast majority of Ursus arctos are not active predators. However, they have the ability to capture anything from rodents to ferocious tigers or large bison. According to the work carried out, the prey consumed comes largely from carrion theft.

Among the mammals that form their diet are hares (Lepus ssp.), Marmots (Marmota ssp.), Pikas (Ochotona ssp.), Mice, ground squirrels and rats. They also eat Himalayan marmots (Marmota himalayana), beavers (Castor spp.), And North American porcupines (Erethizon dorsatum).

Ungulates include bison and deer, with Canadian deer (Cervus canadensis), caribou (Rangifer tarandus) and elk (Alces alces) being their favorites.

Birds

Ursus arctos can eat birds and their eggs. Among the species are Aleutian terns (Onychoprion aleuticus), whooper and trumpeter swans (C. cygnus and Cygnus buccinator), ducks and golden eagles (Aquila chrysaetos), among others.

Behavior

Ursus arctos can be active at various times of the day, but they usually forage for food in the morning and at night, resting in a dense cover, after doing this activity.

It frequently makes seasonal movements, traveling several kilometers in the fall to access areas with greater food availability, such as those with salmon streams.

Occasionally, it can form large groupings, where there are hierarchical positions. These are usually established and maintained aggressively.

Dominance before another male is demonstrated by showing the canines, twisting the muzzle and stretching the neck. During combat, the brown bear uses its paws to hit the opponent on the shoulders or neck and thus be able to bite him on the head.

Large adult males have the highest rank, while those with the lowest rank are adolescents. The females often rival the males, in addition, they are the only ones that establish a bond with their young.

To get around, you do so with a slow, heavy walk, although you may also move quickly. Its behavior is terrestrial, but it can swim and hunt in water.

References

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