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Grizzly bears (Ursus arctos horribilis) are generally larger and heavier than other bears. Adult males average 200 to 300 kilograms (kg) (400 to 600 pounds (lb)) and adult females 110 to 160 kg (250 to 350 lb) in the lower-48 States. Their coloration varies from light brown to nearly black. They can be distinguished from black bears by longer, less curved front claws, humped shoulders, and a facial profile that appears concave. The coat features longer guard hairs over a dense underfur with tips that are usually silver or golden in color hence the name grizzly. Grizzly bears are long-lived mammals, generally living into their mid to late 20s, although some wild bears have lived for over 35 years.
Grizzly bears,Ursus arctos horribilis,are a member of the brown bear species,U. arctos,that occurs in North America, Europe and Asia. The subspeciesU. a. horribilisis limited to North America and historically existed throughout much of the western half of the contiguous United States, central Mexico, western Canada and most of Alaska. Prior to 1800, an estimated 50,000 grizzly bears were distributed in one large contiguous area throughout all or portions of 18 western States, including Washington, Oregon, California, Idaho, Montana, Wyoming, Nevada, Colorado, Utah, New Mexico, Arizona, North Dakota, South Dakota, Minnesota, Nebraska, Kansas, Oklahoma and Texas. Grizzly bears were probably most common in the Rocky Mountains, along the Upper Missouri River and in California. Grizzly bears were less common or did not occur in large expanses of the North American deserts and Great Plains ecoregions.
With the arrival of Europeans to North America, grizzly bears were seen as a threat to livestock and human safety and, therefore, an impediment to westward expansion and settlement. In the 1800s, in concert with European settlement of the American West and government-funded bounty programs which aimed at eradication, grizzly bears were shot, poisoned and trapped wherever they were found. The resulting declines in range and population were dramatic with rapid extinction of populations from most of Mexico and from the central and southwestern United States and California. Grizzly bears were reduced to close to 2% of their former range in the 48 contiguous states by the 1930s, with a corresponding decrease in population, approximately 125 years after first contact with European settlers. In the early 20th century, new regulations were designed to stop future extirpations. In some areas, the protections came too late. By 1975, grizzly bear populations in the 48 contiguous states had been reduced to between 700 to 800. Although significant numbers remained in Alaska and northern Canada, individuals were restricted largely to the confines of national parks and wilderness areas in Washington, Idaho, Montana and Wyoming. Grizzly bears were relegated to these areas in the 48 contiguous states primarily because of limited human influences.
The 1993 U.S. Fish and Wildlife Service Recovery Plan identified six ecosystems, with recovery zones at the core of each, to further recovery efforts. Each recovery zone represents an area large enough and of sufficient habitat quality to support a recovered grizzly bear population. The plan recognized that grizzly bears will move and reside permanently in areas outside the recovery zones and that connectivity between recovery areas would be necessary for isolated populations to increase and sustain themselves at recovery levels.
The recovery zones identified are:
- The Greater Yellowstone, referred to as GYE, in northwestern Wyoming, eastern Idaho and southwestern Montana
- The Northern Continental Divide, referred to as NCDE, of north-central Montana
- The North Cascades area of north-central Washington
- The Selkirks, referred to as SE, area of northern Idaho, northeast Washington and southeast British Columbia
- The Cabinet-Yaak, referred to as CYE, area of northwestern Montana and northern Idaho
- The Bitterroot, referred to as BE, in the Bitterroot Mountains of central Idaho and western Montana.
Currently, there are at least 1,923 individuals in the lower-48 States, with 727 in the GYE demographic monitoring area, 1,092 in the NCDE, about 60 in the CYE, and a minimum of 44 in the United States portion of the SE, although some bears have home ranges that cross the international border (Bjornlie and Haroldson 2021, Costello and Roberts 2021, Kasworm et al. 2021a, Kasworm et al. 2021b). In the GYE, this estimate does not capture the entire distribution of grizzly bears. In addition, grizzly bears have been verified in areas between ecosystems; however, there are likely few resident bears in the lower-48 States outside of the GYE, NCDE, CYE, and SE. There are curr
Ursus arctos horribilis
Grizzly bears hibernate in winter; hibernation is a life history strategy bears use to cope with seasons of low food abundance. In preparation for hibernation, bears increase their food intake dramatically during a period called hyperphagia. Hyperphagia occurs throughout the 2 to 4 months prior to den entry, which runs August through November. During hyperphagia, excess food is converted into fat, and grizzly bears may gain as much as3.64 pounds a day (1.65 kilograms a day). Grizzly bears must consume foods rich in protein and carbohydrates in order to build up fat reserves to survive denning and post-denning periods. Fat stores are crucial to the hibernating bear as they provide a source of energy and insulate the bear from cold temperatures, and are equally important in providing energy to the bear upon emergence from the den when food is still sparse relative to metabolic requirements. However, we are unaware of a minimum body fat threshold for survival during the denning period and documentation of natural mortality in independent-age bears is low for non-collared individuals.
Grizzly bears in the 48 contiguous states hibernate in dens for 4 to 6 months each year, typically entering dens between October and December, with males entering their dens later than females. Females give birth to cubs in the den in late January to early February. On average, males exit dens from early March to late April. Females typically emerge from their dens from mid-March to mid-May, with females with cubs emerging later from mid-April to late-May.
Grizzly bears typically hibernate alone in dens, except for females with young and subadult siblings who occasionally hibernate together. Grizzly bears usually dig dens on steep slopes where wind and topography cause an accumulation of deep snow and where the snow is unlikely to melt during warm periods. Most dens are located at higher elevations, above 8,000 feet (2,500 meters) in the Greater Yellowstone Ecosystem and 6,400 feet (1,942 meters) in the Northern Continental Divide Ecosystem, and on slopes ranging from 30 to 60 degrees. In the Cabinet-Yaak Ecosystem, the majority of den sites occurred above 5,248 feet (1,600 meters), often on northerly and easterly aspects, though all aspects were used. In the Selkirks Ecosystem, the majority of dens were located above 5,248 feet (1,600 meters), often on easterly aspects, but all aspects were used. The North Cascades Ecosystem contains large areas at high elevations with isolated, steep, snow-packed slopes and many natural caves to serve as potential den sites. Additional areas associated with ridge systems stemming from major volcanic peaks may provide den sites at lower elevations within the North Cascades. In 1991, Davis and Butterfield assessed the northern part of the Bitterroot Ecosystem recovery zone and areas to the immediate north, and concluded that deep snow and mountainous terrain provides adequate denning habitat.
Denning increases survival during periods of food scarcity and inclement weather. During this period, bears do not eat, drink, urinate or defecate. Hibernating grizzly bears exhibit a marked decline in heart and respiration rate, but only a slight drop in body temperature. Due to their relatively constant body temperature in the den, hibernating grizzly bears may be aroused and have been known to exit or relocate dens when disturbed by seismic or mining activity or other human activities. Dens are rarely used twice by an individual, although individuals usually use the same general area from year-to-year. Females display stronger area fidelity than males and generally stay in their dens longer, depending on reproductive status. Females with cubs usually spend a few weeks close to their den upon emergence, unlike solitary bears.
Size & Shape
They can be distinguished from black bears by longer, less curved front claws, humped shoulders, and a more concave facial profile.
Grizzly bears are generally larger and heavier than other bears. Adult males average 400 to 600 pounds (200 to 300 kilograms) and adult females 250 to 350 pounds (110 to 160 kilograms) in the 48 contiguous states.
Color & Pattern
Their coloration varies from light brown to nearly black.The coat features longer guard hairs over a dense underfur with tips that are usually silver or golden in color – hence the name grizzly.
The 48 contiguous statesprovides highly diverse landscapes which contain a wide array of habitat types and bear foods across and within the ecosystems. Plant communities vary from grasslands at lower elevations, which are defined as less than6,230 feet(1,900 meters) to shrub fields that are created by fires, avalanches or timber harvest, to conifer forests at mid-elevations and subalpine and alpine meadows at higher elevations, defined as greater than 7,870 feet (2,400 meters). Grizzly bears are opportunistic omnivores and display great diet plasticity - even within a population. As such, individuals shift their diet according to foods that are most nutritious, for example, available foods that are high in fat, protein, and, or, carbohydrates.An extensive literature review documented more than 260 species of foods that grizzly bears consume in the Greater Yellowstone Ecosystem, which represents four of the five kingdoms of life.The ability to use whatever food resources are available is likely one reason brown bears are the most widely distributed bear species in the world, occupying habitats from deserts to alpine mountains and everything in between. This ability to live in a variety of habitats and eat a wide array of foods makes grizzly bears a generalist species. In contrast, specialist species like mountain lions, eat only a few specific foods or live in only one or two specific habitat types. Morphological adaptations that support a diverse diet include crushing molars and the greatest intestinal length relative to body length of any carnivore.
Grizzly bear diets are highly variable among individuals, seasons and years, and between ecosystems. They opportunistically seek and consume whatever plant and animal foods are available to them. Grizzly bears will consume almost any food available including living or dead mammals or fish, insects, worms, plants, human-related foods and garbage. In areas where animal matter is less available, berries, grasses, roots, bulbs, tubers, seeds and fungi are important in meeting protein and caloric requirements. Grizzly bears often sample new foods so that they have alternative options in years when preferred foods are scarce. In the Greater Yellowstone Ecosystem, it has been noted that, after 10 years of food habits data collection, new feeding strategies continued to appear annually in this population.
In addition, grizzly bears opportunistically prey on livestock, agricultural crops, like grain, corn, garbanzo beans and melons, as well as other human foods. Cattle and sheep depredation rates are generally higher where bear densities are higher, and in later summer months. In the Greater Yellowstoneand Northern Continental Divide ecosystems, depredation is generally higher where livestock is more abundant, such as areas with livestock allotments and privately owned ranchland. Livestock grazing is less common in the Cabinet-Yaak and Selkirks ecosystems, and depredation rates are correspondingly lower. Grizzly bears also opportunistically prey on small livestock, such as chickens, llamas, and goats, which primarily occur on private land.
Food resources are especially important during the period leading up to hibernation when grizzly bears must consume energetically rich foods to build up fat reserves to survive denning and post-denning periods. Fat stores provide a source of energy and insulate the bear from cold temperatures during hibernation. Also, fat stores obtained by female grizzly bears at the end of fall are positively correlated with earlier birth dates and quicker growth rates of their cubs. Additionally, a body fat threshold may exist below which females may not produce cubs, even when bred; studies have shown that females with less than 20% body fat are unlikely to produce cubs.However, we are unaware of a minimum body fat threshold for survival during the denning period.
Grizzly bears have three life stages: dependent young, subadults and adults. Dependent young are usually less than 2 years old and depend on and are associated with their mother, relying on her for food, protection, and survival. There are two primary sub-categories of dependent young: cubs, defined as cubs born during the most recent denning season and less than one year old, and yearlings.
Grizzly bears have a promiscuous mating system. Mating occurs from May through July, with a peak in mid-June. Although females mate in spring and early summer, their fertilized embryos do not implant into the uterus for further development until late fall. Fat stores obtained by female grizzly bears at the end of fall are positively correlated with earlier birth dates and faster growth rates of their cubs. Additionally, a body fat threshold may exist below which females may not produce cubs, even when bred. Cubs are born in the den in late January or early February and nurse for 3 to 4 months inside the den and after den emergence, but also increasingly eat foods with their mother once outside the den. Yearlings den with their mother but do not nurse in the den. Outside of the den, yearlings eat the same foods as their mother, but also occasionally nurse.
Shortly after den emergence, 2-year-old offspring generally leave their mother to become subadults. Subadults are typically not sexually mature enough to breed; however, a small percentage of 3-year-old females do breed and produce cubs as 4-year-olds. Some subadults, generally males, may disperse away from their mother and establish their own home range.
Adult bears are more than 4-years-old and have reached sexual maturity. Some bears may not breed until they are older than 5-years-old, but they have the ability to reproduce once they reach the adult stage. Adults generally live into their mid- to late-20s, although some wild bears have lived over 35 years. Female reproductive senescence starts around age 25 for those long-lived individuals.
Age of first reproduction, which averages 5.8 to 6.3 years, litter size, which averages 2.1 to 2.19 cubs per litter, and inter-birth interval, which is the average number of years between litters, averages 2.78 to 3.4 years, may be related to nutritional state and, or, density dependent effects and varies between ecosystems. Grizzly bears have one of the slowest reproductive rates among terrestrial mammals, resulting primarily from these reproductive factors: late age of first reproduction, small average litter size and the long inter-birth interval. Given these factors, it may take a female grizzly bear 10 or more years to replace herself in a population. The slow reproductive rate should also be understood in the context of having one of the longer life spans of terrestrial mammals. To that end, Ursus arctos in 90th percentile for longevity. With a population being made up of numerous overlapping generations, it is possible for mothers, daughters and granddaughters to be reproductively active at the same time. Grizzly bear females typically cease reproducing some time in their mid-to-late 20s.
Grizzly bears are long-lived mammals, generally living to be around 25 years old, although some wild bears have lived for over 35 years.
Grizzly bears use a variety of habitats. In general, a grizzly bear’s individual habitat needs and daily movements are largely driven by the search for food, water, mates, cover, security or den sites. The available habitat for bears is also influenced by people and their activities. Human activities are the primary factor impacting habitat security and the ability of bears to find and access foods, mates, cover and den sites. Other factors influencing habitat use and function for grizzly bears include overall habitat productivity, which is defined by food distribution, quality and abundance. Overall habitat productivity is also defined by the availability of habitat components, like denning areas and cover types. Additionally, grizzly bear social dynamics, learned behavior and preferences of individual grizzly bears, as well as grizzly bear population density and random variation are important aspects. Water is an important habitat requirement as well; however, we have no information to suggest that water is limiting in the habitat that bears currently occupy, but may have limited distribution in portions of historical range.
Grizzly bears use a variety of cover types to rest and shelter. Grizzly bears often select bed sites with horizontal and vertical cover, especially at day bed sites suggesting that bed site selection is important for concealment from humans. The interspersion of open areas as feeding sites associated with cover are important, probably because diverse habitat complexes, such as forest interspersed with moist grass-forb meadows, provide both abundant food and cover. Generally, areas with vegetative cover are important to grizzly bears for use as bedding sites. Beds underneath any type of vegetative cover, not necessarily always forest cover, provide bears shade during the hottest parts of the day and a place to sleep at night.
The six ecosystems occur in mountainous ecoregions and each ecosystem provide the habitat heterogeneity necessary for adequate food, denning and cover resources. Because there are limited opportunities to increase or control these habitat components, the objective for grizzly bear habitat management has been, and continues to be, to reduce or mitigate the risk of human-caused mortality and displacement. An effective habitat management tool for reducing grizzly bear mortality risk on public lands is managing motorized access to ensure bears have secure areas away from humans.
Unmanaged motorized access:
- Increases human interaction and potential grizzly bear mortality risk
- Increases displacement from important habitat
- Increases habituation to humans
- Decreases habitat where energetic, meaning food, requirements can be met.
Managing motorized access on public lands helps ameliorate these impacts. Other habitat management tools that minimize displacement and reduce grizzly bear mortality risk include regulating livestock allotments and developed sites on public lands. Implementing food storage orders on public lands also reduces mortality risk for both humans and grizzly bears. Requiring users and recreationists in grizzly bear habitat to store their food, garbage and other bear attractants in bear-proof, inaccessible ways reduces encounters and human-grizzly bear conflicts. In addition, encouraging users and recreationists to carry bear spray, and know how to use it, helps reduce the potential for injury to people and bears.
Adult grizzly bears are normally solitary except when breeding or when females have dependent young, but they are not territorial and home ranges of adult bears frequently overlap. Home range size is affected by resource availability, sex, age and reproductive status. Generally, females with cubs-of-the-year or yearlings have the smallest home range sizes. The large home ranges of grizzly bears, particularly males, enhance maintenance of genetic diversity in the population by enabling males to mate with numerous females.
Young, female grizzly bears usually establish home ranges within or overlapping their mother’s. This pattern of home range establishment can make dispersal of females across landscapes a slow process. Radio-telemetry and genetic data suggest females typically establish home ranges an average of 6.1 to 8.9 miles (9.8 to 14.3 kilometers) away from the center of their mother’s home range, whereas males generally disperse farther, averaging 18.6 to 26.0 miles (29.9 to 42.0 kilometers) away from the center of their mother’s home range. Maximum male dispersal distances of 42 to 109 miles (67 to 176 kilometers) have been documented in the Greater Yellowstoneand Northern Continental Divide ecosystems. Studies also indicate that females can and do disperse long distances up to 50 to 56 miles (80 to 90 kilometers), typically on the periphery of expanding populations. Although the frequency of long-distance dispersal by females is much lower than males, it can contribute to range expansion and demographic connectivity between populations.
Home range sizes vary among the ecosystems because of population densities and habitat productivity, as well as methodology. In the 48 contiguous states, observed average annual adult female home ranges vary from 130 to 358 kilometers-squaredand average annual adult male home range vary from 475 to 2,162 kilometers-squared.
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Regulatory Status Change
The grizzly bear (Ursus arctos horribilis), also known as the North American brown bear or simply grizzly, is a population or subspecies of the brown bear inhabiting North America.What is the current population of grizzly bears Ursus arctos horribilis in the United States? ›
There are an estimated 55,000 grizzly bears in North America. In the United States, that population is limited to Alaska, Idaho, Montana, Washington, and Wyoming.Are grizzly bears endangered 2022? ›
In the U.S., the grizzly bear is protected as a threatened species under the Endangered Species Act. As a result of their dwindling numbers, fewer than 1,500 grizzlies are left in the lower 48 states and about 31,000 in Alaska.Who would win in a fight a gorilla or a bear? ›
Although a silverback gorilla is very fast, quite strong, and has a longer arm span, it is unlikely that a silverback could defeat the much larger and faster grizzly bear in a fair fight. The one advantage that a Silverback might have is in the enormous strength of its muscles.What does arctos mean in Greek? ›
Etymology. Learned borrowing from Ancient Greek ἄρκτος (árktos, “bear”).What bear species kills the most humans? ›
Grizzly and polar bears are the most dangerous, but Eurasian brown bears and American black bears have also been known to attack humans.Which state has the most grizzly bear attacks? ›
Alaska is the US state with the most bear attacks.
The most updated bear attacks in Alaska statistics reveal that Alaska accounts for 29.6% of all fatal bear attacks in the US. Alaska is one of the few places in the country that has all three species of North American bears living in it: Black Bears. Grizzly Bears.
The Arctotherium angustidens could weigh up to 4,000 pounds and towered over many other animals that lived at the time. Now extinct, the Arctotherium angustidens is distantly related to the modern Spectacled bear.Why is bear meat poisonous? ›
As omnivores, bears often carry the larvae of a nasty parasite, Trichina spiralis. Eating undercooked bear meat can cause trichinosis, which can cause severe sickness or even death in humans. That's why bear is most often cooked in stews, chilis, braises, or in well-cooked sausage.Can humans drink bear milk? ›
Bear milk is the most nutrient-rich milk in the animal kingdom. It also happens to be absolutely delicious, offering a rich, nutty, and satisfying taste.
To scare the bear away, make loud noises by yelling, banging pots and pans or using an airhorn. Make yourself look as big as possible by waving your arms. If you are with someone else, stand close together with your arms raised above your head.What is the most endangered animal in the world? ›
1. Javan Rhinos. Once found throughout south-east Asia, Javan rhinos have suffered a staggering decline in their numbers due to hunting and habitat loss. The lone wild population of Javan rhinos is one of the rarest of the rhino species—around 75 individuals—which can only be found on the island of Java, Indonesia.Will the California grizzly come back? ›
Biologists believe there is potential for a good enough DNA extraction to bring back the California Grizzly Bear.What animal can beat a grizzly bear? ›
5 Animals That Could Defeat A Grizzly Bear - YouTubeCould a human knock out a gorilla? ›
Highly unlikely, if no firearms or tranquilizer guns are involved. A gorilla can reach speeds of 20 mph to 25 mph. In comparison, Usain Bolt's record in the 100-meter dash roughly translates into 23 mph (Bolt reaches peak speeds of around 27 mph—but still).Who would win a fight between a grizzly bear and a tiger? ›
Can a Siberian tiger kill a fully grown male grizzly bear? Probably, but that would most definitely be through ambush. If this were a face-to-face fight, the bear would be the one to triumph over the tiger more times than not. Just look at the sheer strength of them.Why is grizzly bear called horribilis? ›
Naming. The word "grizzly" in its name refers to "grizzled" or grey hairs in its fur, but when naturalist George Ord formally named the bear in 1815, he misunderstood the word as "grisly", to produce its biological Latin specific or subspecific name "''horribilis''".What is the Old Norse word for bear? ›
A phonetically exact correspondence exists in Old Norse bjǫrn (“bear”), from Proto-Germanic *bernuz (more at *berô), but the English word is never used for "bear", and the Old Norse word is never used for "warrior".What is the Latin name for bear? › › Factsheet › Bear (Grizzly) ›
Bear (Grizzly) - Related Species
Grizzly Bear Animal Facts | Ursus Arctos Horriblis
Grizzly bear guide: where they live, how they hunt and conservation
Ursus is Latin for "bear" arctos comes from Greek arktos, meaning bear.What does Ursus arctos represent? ›
The brown bear (Ursus arctos) is a large bear species found across Eurasia and North America.Why is it called Ursus arctos? ›
The scientific name for the grizzly bear, Ursus arctos, comes from the Latin word, ursus, meaning bear and the Greek word, arctos, also meaning bear (Wallace, 1997). The closet relative to the grizzly bear is the polar bear.Why are brown bears called Ursus arctos? ›
The scientific name of the brown bear, Ursus arctos, comes from the Latin ursus, meaning "bear", and from ἄρκτος arktos, the Greek word for bear.What is the Old Norse word for bear? ›
A phonetically exact correspondence exists in Old Norse bjǫrn (“bear”), from Proto-Germanic *bernuz (more at *berô), but the English word is never used for "bear", and the Old Norse word is never used for "warrior".What is the Norse name for bear? ›
It is the Icelandic and Swedish (Björn) and Danish, Norwegian and Faroese (Bjørn) word for a bear.
Yet, the truth is that both animals are relatively closely related! Dogs and bears are both within the suborder Caniformia (literally meaning dog-like carnivorans. This taxonomical classification includes dogs, bears, wolves, foxes, raccoons, and mustelids.What does a bear symbolize spiritually? ›
On a spiritual level, the bear represents the courage to evolve and the ability to be open-minded. In addition, the bear reminds us to trust our instincts and to be protective of our faith.What do bears symbolize in Greek mythology? ›
In the myths of Ancient Greece, bears were considered an attribute of certain deities. One of these was Artemis, the goddess protector of animals and hunting, who is represented as a bear together with her priestesses, sometimes known as “little she-bears”.What is the oldest bear on earth? ›
Debby (polar bear)
|Debby in 2008|
|Died||17 November 2008 (aged 41–42) Winnipeg, Manitoba, Canada|
|Known for||Oldest polar bear recorded|
|Residence||Assiniboine Park Zoo|
The spirit bear, also known as the Kermode bear, is the rarest bear in the world and a subspecies of the black bear found only in this small part of British Columbia.What to do if you see a brown bear? ›
Remain still; stand your ground but slowly wave your arms. Help the bear recognize you as a human. It may come closer or stand on its hind legs to get a better look or smell. A standing bear is usually curious, not threatening.Can a lion beat a brown bear? ›
A bear would win a fight against a lion. Bears have the advantage in just about every aspect, from size to offensive capabilities. The only time that a lion would win is if it managed to sneak up and ambush a bear, leaping onto it and biting into its head with such power that it shattered the skill.What's bigger a grizzly or Kodiak? ›
Kodiak bears are sometimes called grizzlies, due to superficial physical similarities with grizzly bears (Ursus arctos horribilis). However, Kodiak bears are larger than grizzly bears, and the ranges of these two subspecies do not overlap.What is the biggest brown bear in the world? ›
Kodiak bears are the largest bears in the world. A large male can stand over 10' tall when on his hind legs, and 5' when on all four legs. They weigh up to 1,500 pounds. Females are about 20% smaller, and 30% lighter than males.