GRIZZLY BEAR: CHARACTERISTICS, HABITAT, FEEDING, BEHAVIOR - BIOLOGY - 2025

The grizzly bear (Ursus arctos horribilis) is the North American subspecies of the brown bear (Ursus arctos). The main characteristic that distinguishes it is its hump, being a muscle mass that is on its shoulder and is used to drive the movement of the front legs, especially when digging.

In relation to its geographical distribution, it is found from Alaska to Yukon and the Northeast Territories, through Alberta and British Columbia. In the United States, there are some isolated communities in Idaho, Wyoming, Washington, and Montana.

Grizzly bear. Source: Chris Servheen / USFWS

The grizzly bear's favorite habitats are the open, meadows, and low alpine regions. In relation to the winter den, they dig it in the ground, usually on the slopes. Due to its large size, it is the second largest bear in North America, after the polar bear.

As for food, it is an omnivorous animal, whose diet depends on the seasons and the region where it lives. Thus, Ursus arctos horribilis eats insects, fish, birds, some small mammals, fruits, seeds, berries, and fungi. However, their favorite food is salmon.

General characteristics

Grizzly bear. Source: Rafael Mauricio Marrero Reiley. Own authorship

His body is large, robust and muscular. It has a particular hump on its shoulder, which is the main characteristic of this subspecies. This muscle mass is used during excavation, since it drives the action of the front extremities.

The claws on the front legs measure between 5 and 10 centimeters, so when walking they leave a deep mark on the ground. This bear uses its front legs and claws to dig in the ground, looking for plant roots, bulbs and some marmots found in its burrow.

As for its head, it is large, with a concave facial profile. The ears are short and rounded. Ursus arctos horribilis has very strong teeth, with large incisors and prominent canines.

As for the molars, the first 3 located in the upper jaw have a crowned root and are underdeveloped.

Coloration

The coat can vary from blond, through a variety of brown tones, to a more intense brown, almost black. The protective hairs are gray or silver, giving the animal a gray effect. In relation to the legs, they are generally darker than the rest of the body.

The difference in hair shades is influenced by nutrition, shedding, and weather conditions.

Size

Ursus arctos horribilis has a very marked sexual dimorphism, since the male can be almost twice as heavy as the female. Thus, the male measures between 1.98 and 2.4 meters and can weigh between 181 and 363 kilograms, with exceptional cases in which they reach up to 680 kilograms.

As for the female, her body has an approximate length of 1.2 to 1.8 meters, weighing between 131 and 200 kilograms.

Locomotion

The grizzly bear is a plantigrade animal, since when it walks it does so fully supporting the soles of its legs. When the animal moves at slow or moderate speeds, it does so using walking, rather than trotting. Also, use the gallop and brisk walk.

The reason for not using the trot could be associated with some morphological or energetic characteristics. In this sense, the high mean forces may be due to the movement of the frontal plane of the elbow and the carpus. In addition, experts point out that the reaction force is greater in the rear extremities than in the front ones.

Inactivity stage

During winter, the ambient temperature drops, the territories are covered with snow and food becomes scarce. In the cold season, grizzly bears take shelter in their burrows, where they enter a dormant period.

In this stage, which can last from three to six months, there are organic variations in the bear. These include a decrease in respiratory and heart rates and a slight drop in body temperature.

Also, while in the winter den, the animal does not eat or drink water. They also do not defecate or urinate. Because the temperature does not drop markedly, Ursus arctos horribilis can easily wake up and leave the cave.

Organic adaptations

Recently, a group of researchers conducted a study on the cardiovascular physiology of the heart of Ursus arctos horribilis, while it was in an inactive state.

As a result of this work, experts point to a notable change in the operation of the atrial chamber. The fraction of emptying of the left atrium was markedly reduced, compared to the parameters corresponding to the active state of the animal.

Thus, variations in the diastolic cardiac filling cycle could be the most relevant macroscopic functional change in the winter inactivity stage.

In this way, specialists conclude that changes in the operation of the atrial chamber is an important adaptation, since it brings numerous advantages to the body. Among these is the fact that it prevents the dilation of said chamber, allowing the myocardium to conserve energy.

In this way, the heart remains healthy during the time when heart rates are very low.

State of conservation

wikimedia commons

The population of Ursus arctos horribilis has decreased in some of the areas where it is distributed, although in others it is stable. However, this subspecies is considered threatened with extinction in much of the United States and Canada.

U.S

The U.S. Fish and Wildlife Service included the grizzly bear on the List of Endangered and Threatened Wildlife in the Greater Yellowstone Ecosystem. So it is considered illegal to injure, harass or kill this mammal, unless it is in self-defense or that of others.

The situation in Washington is dire. This subspecies is extinct in most of that state, with the exception of a few populations found in the North Cascades and the Selkirk Mountains.

This motivated that, in 1975, it was included within the group of animals threatened with extinction, under the Federal Law of Endangered Species.

Canada

In Canada, the National Committee on the Status of Canada's Endangered Wildlife (COSEWIC) declared Ursus arctos horribilis of special concern in the territories and provinces of Yukon, Nunavut, British Columbia, and Alberta.

This categorization is based on the fact that the natural development of the bear is sensitive to natural events and different human activities in the areas where it lives.

According to protectionist organizations, the grizzly bear is currently not in serious danger of extinction. However, these organisms consider it necessary to attack the threats that afflict the subspecies, in order to prevent the situation from worsening.

Threats

The main problem that influences the decline of the grizzly bear population is the degradation of its natural habitat. Man has cut down and deforested the forests, to use the soils for agricultural and urban purposes.

The construction of roads not only alters the ecosystem, but can cause the accidental death of the animal, when it tries to cross the road to reach the other side of the forest.

Furthermore, in some regions, oil, gas and mining industries have developed. This pollutes the environment and fragments biomes, disturbing them.

One of the consequences of habitat loss is the possible isolation of the population, which hinders their reproduction and therefore the natural recovery of the community.

This situation is exacerbated by the grizzly bear's low reproductive rate and the late age at which it becomes sexually mature. Likewise, under this circumstance, this mammal could suffer from genetic isolation.

Another factor that affects Ursus arctos horribilis is its illegal hunting, to commercialize its skin, legs and claws. It can also be killed when attempting to enter urban areas in search of food.

Conservation activities

National and international organizations, as well as the governments of the different regions are working hard in the recovery of the grizzly bear populations. Thanks to these actions, in Wyoming and Montana the communities of this subspecies have doubled.

The wildlife agencies of Washington, Idaho, and British Columbia have established various recovery areas where this mammal has the best chance to develop.

Other activities aimed at protecting this subspecies are educational projects. These are directed towards the education of tourists and visitors to the national parks and towards residents of the areas surrounding the natural habitat where they live.

One of these plans is the Grizzly Bear Outreach Project, currently known as Western Wildlife Outreach. They work specifically with the communities of people living in the Selkirk Mountains in Canada and the North Cascades in the United States.

Habitat and distribution

Yellowstone National Park from Yellowstone NP, USA

Distribution

Historically, Ursus arctos horribilis was distributed from Alaska to Mexico and from the Mississippi River to the Pacific Ocean. However, its population has been notably reduced.

Thus, it currently extends from Alaska to the Northwest Territories and Yukon, south through British Columbia and into the western region of Alberta. There are some isolated populations northwest of Washington, western Montana, northern Idaho, northwest Wyoming, and probably southern Colorado.

Habitat

The grizzly bear prefers open, shrubby habitats, meadows, and low elevation alpine areas. During spring, it lives in riparian areas, floodplains, and wet meadows. In the summer, it is located in high elevation meadows and in open, grassy regions.

Although wood is a very important element within the habitat, this subspecies is usually found in more open regions or in wooded areas, which have areas interspersed with grasses and bushes.

However, it is also sighted in thickets, with low shrubs and in high altitude riverside communities.

Among the timber plants that exist in the areas where it inhabits are: the subalpine fir (Abies lasiocarpa), the white bark pine (Pinus albicaulis), the fir (Picea spp.) And the western red cedar (Thuja plicata).

As for the resting areas, during the day the grizzly bear is located in territories that are close to the feeding sites. Winter dens are dug by the animal, usually on slopes. Also, these can be established in fallen trees and in caves.

Taxonomy

-Animal Kingdom.

-Subreino: Bilateria.

-Filum: Cordate.

-Subfilum: Vertebrate.

-Superclass: Tetrapoda.

-Class: Mammal.

-Subclass: Theria.

-Infraclass: Eutheria.

-Order: Carnivora.

-Suborder: Caniformia.

-Family: Ursidae.

-Gender: Ursus.

-Species: Ursus arctos.

-Subspecies: Ursus arctos horribilis.

Reproduction

US Forest Service

The female grizzly bear reaches sexual maturity between 5 and 8 years of age. Members of this subspecies have one of the slowest reproductive rates of land mammals.

This is due to the small size of the litter, the late age at which they start their reproduction and the long interval between births.

The mating system is polygynous, where a female can copulate with several males in the same reproductive period. In this way, the puppies of a litter could have different parents.

Ap

The cubs are born in the den in late January or early February. These stay with the mother for two or three years. At that time, the female fiercely defends them, but at the end of that stage of care drives them away from her side.

As long as the mother and her young are together, the female does not mate. This is one of the reasons why the grizzly bear is characterized by a slow reproductive rate.

Feeding

- Nutritional regimen

Ursus arctos horribilis is an opportunistic omnivore, whose diet is highly variable, since it depends on the regions where it lives and the seasons.

Its diet is very wide, and can include small mammals, insects and their larvae, such as the ladybug beetle, fish, some species of birds and carrion.

In those areas where animals are not abundant, you can eat berries, seeds, bulbs, roots, grass, fruits, mushrooms, tubers, and nuts. Some of the more common plant species are hawthorn (Crataegus spp.), Canadian bison cherries (Shepherdia canadensis), and honeysuckle (Lonicera spp.).

Also consume June strawberry (Amelanchier alnifolia), pine (Pinaceae), willow (Salix spp.), Blueberry (Vaccinium spp.), Dandelion (Taraxacum spp.), Spearmint (Heracleum spp.), Horsetail (Equisetum spp.) And strawberry (Fragaria spp.).

In the event that natural sources of food become scarce, the grizzly bear ventures into orchards and farms, in search of bee hives, vegetable crops, fruits, vegetables and livestock. This causes serious conflicts with humans, who hunt them to defend their life, their crops and animals.

- Feeding Habits

Members of this subspecies often store their food, especially carrion, in shallow holes, which they cover with various grasses and mosses. These plant species act as preservatives.

If the prey lives in an underground burrow, is hidden underground or in the roots of trees, the bear uses its powerful front legs and strong claws to burrow and capture it, just as it does with rodents.

Regions

In Idaho and Washington, the grizzly bear diet includes at least 10% fish or meat, especially elk and deer carrion. For those who live in Alaska and Canada, one of the most important food sources is salmon.

Another animal that provides you with a large amount of nutrients is the armyworm moth (Spodoptera exigua). During the summer time in Yellowstone, this placental mammal can consume up to 20,000 of these moths daily.

Seasons

During the spring, the grizzly bear visits wetlands, looking for succulents that are easy to digest and are high in nutrients. In the summer, their diet includes thistles, mushrooms, roots, fish, insects, and wild berries.

The feeding of Ursus arctos horribilis in the autumn season includes ants and berries, among others. During the last weeks of summer and fall, it stores large amounts of fat, which will be used during its dormant state, which occurs in winter.

Behavior

The grizzly bear is considered a solitary animal, except when a mother raises the cub, and they can stay together for up to three years. However, it can sometimes form food groups.

In those places in Alaska where salmon spawn during the summer, dozens of these bears can congregate to catch and eat their favorite food.

This North American mammal is a curious animal and has the ability to remember the location of food sources. His sense of vision is excellent, as is his sense of hearing and smell.

Generally, the territorial ranges of adults may overlap, however, they are not considered territorial. Its period of greatest activity occurs during the day and night hours. However, in urbanized areas these habits tend to change, to avoid contact with man.

At times of the day when it is extremely hot, as is often the case at midday, the bear heads to areas where the vegetation is dense, including alders, tall grass and willows. There, it rests on a group of leaves that it has accumulated, forming a kind of bed.

Communication

The bear's body language can give signals that reflect its mood. These large mammals can stand up on their two hind legs, with the intention of having a better view of the area, although it could be interpreted as a sign of aggression.

However, when he is excited, he shakes his head, vocalizes snorts, and grinds his teeth.

References

1. Snyder, SA (1991). Ursus arctos horribilis. Fire Effects Information System. US Department of Agriculture, Forest Service, Rocky Mountain Research Station, Fire Sciences Laboratory (Producer). Recovered from fs.fed.us.
2. ECOS (2019). Grizzly bear (Ursus arctos horribilis). Recovered from ecos.fws.gov.
3. Helmenstine, Anne Marie (2019). Grizzly Bear Facts (Ursus arctos horribilis). ThoughtCo. Recovered from thoughtco.com.
4. ITIS (2019). Ursus arctos horribilis. Recovered from itis.gov.
5. S. Fish and Wildlife Service (2019). Grizzly bear (Ursus arctos horribilis). Recovered from fws.gov.
6. Encyclopaedia Britannica (2019).Grizzly bear. Recovered from britannica.com.
7. Derek Stinson, Gary Wiles, Gerald Hayes, Jeff Lewis, Lisa Hallock, Steve Desimone, Joe Buchanan (2013). Grizzly Bear (Ursus arctos horribilis). Washington Department of Fish and Wildlife. Recovered from eopugetsound.org.
8. Catherine L. Shine, Skylar Penberthy, Charles T. Robbins, O. Lynne Nelson, Craig P. McGowan (2015). Grizzly bear (Ursus arctos horribilis) locomotion: gaits and ground reaction forces. Recovered from jeb.biologists.org.
9. Bear conservation (2019). Grizzly Bear. Recovered from bearconservation.org.uk.
10. Western Wildlife Outreach (2019).Grizzly bear (Ursus arctos horribilis). Recovered from westernwildlife.org.