---
title: "What the sources say about the Grizzly Bear | AnimalTracks.wiki"
description: "48 claims from the Grizzly Bear profile, each beside the words of the source that backs it."
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# What the sources say about the Grizzly Bear (*Ursus arctos horribilis*)

> 48 claims from the Grizzly Bear profile, each beside the words of the source that backs it. A "..." marks a cut in a quote and [brackets] an insertion.

Profile: [Grizzly Bear](https://animaltracks.wiki/animals/grizzly-bear/)

## Ursus arctos (brown bear). Animal Diversity Web, University of Michigan.

https://animaldiversity.org/accounts/Ursus_arctos/

| The page says | The source says |
| :--- | :--- |
| The IUCN rates the whole species, Ursus arctos, as Least Concern worldwide | IUCN Red List Least Concern |
| dig a ground squirrel out of its burrow | also dig mice, ground squirrels, marmots, and other fossorial animals out of their burrows |

## Ursus arctos horribilis (Grizzly Bear). U.S. Fish and Wildlife Service, Species Profile.

https://www.fws.gov/species/grizzly-bear-ursus-arctos-horribilis

| The page says | The source says |
| :--- | :--- |
| In the lower 48 states, an adult male grizzly averages 400 to 600 pounds (200 to 300 kilograms) and an adult female 250 to 350 pounds (110 to 160 kilograms) | 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. |
| At least 1,923 grizzlies live in the lower 48 states, and the U.S. Fish and Wildlife Service lists that population as threatened | Currently, there are at least 1,923 individuals in the 48 contiguous states ... Grizzly bears in the 48 contiguous states are currently protected as a threatened species. |
| dig its den, usually on a steep slope | Grizzly bears usually dig dens on steep slopes |
| In preparation for hibernation, a grizzly goes through hyperphagia, a feeding binge in the two to four months before it enters its den | In preparation for hibernation, bears increase their food intake dramatically during a period called hyperphagia. Hyperphagia occurs throughout the two to four months prior to den entry |
| female grizzlies with less than 20 percent body fat are unlikely to produce cubs, even when they have mated | 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 |
| For four to six months in the den, a grizzly does not eat, drink, urinate, or defecate | hibernate in dens for four to six months each year ... During this period, bears do not eat, drink, urinate or defecate. |
| During hyperphagia, the fall feeding binge that fattens bears up for hibernation | In preparation for hibernation, bears increase their food intake dramatically during a period called hyperphagia. ... During hyperphagia, excess food is converted into fat |

## Yellowstone Grizzly Bear Facts. National Park Service, Yellowstone National Park (Yellowstone Science 23(2)).

https://www.nps.gov/yell/learn/yellowstone-grizzly-bear-facts.htm

| The page says | The source says |
| :--- | :--- |
| claws built for digging | claw length and shape allow efficient digging of foods from the ground |
| a fall feeding binge of about 20,000 calories a day | hyperphagia: 20,000 kcal/day |
| Yellowstone grizzlies' claws, up to 5.9 inches long, are shaped for digging food out of the ground | Claw Length: average 1.8 inches (45 mm), longest 5.9inches (150 mm);claw length and shape allow efficient digging of foods from the ground |
| they can run 35 to 40 miles an hour | Speed: 35-40 mph |
| In Yellowstone, grizzly claws average 1.8 inches (45 millimeters), and the longest measured 5.9 inches (150 millimeters) | Claw Length: average 1.8 inches (45 mm), longest 5.9inches (150 mm) |
| Their length and shape make them good for digging food out of the ground but worse than a black bear's for climbing trees | claw length and shape allow efficient digging of foods from the ground but are less efficient for tree climbing than black bear claws |
| the National Park Service lists a Yellowstone grizzly's top speed at 35 to 40 miles an hour | Speed: 35-40 mph |
| Yellowstone's figures put its intake at about 20,000 calories a day during hyperphagia, more than double the 5,000 to 8,000 it eats on a normal day | Caloric Requirements: normal (May-Sept): 5,000-8,000 kcal/day; hyperphagia: 20,000 kcal/day |
| Grizzlies are shallow hibernators | bears are shallow hibernators |
| body temperature dropping only a few degrees, from 36.5 to 38.5°C in the active season to 34.4 to 35°C in hibernation, while heart rate falls from 40 to 50 beats a minute to 8 to 19 | Body Temperature: 36.5-38.5°C (98-101°F) during active season;34.4-35°C (94-95°F) during hibernation ... Heart Rate: 40-50 beats per minute; 8-19 beats per minute during hibernation |
| a grizzly bear's calorie intake can climb to about 20,000 calories a day, more than double the 5,000 to 8,000 calories it eats on a normal day | Caloric Requirements: normal (May-Sept): 5,000-8,000 kcal/day; hyperphagia: 20,000 kcal/day |

## Brown Bears. National Park Service.

https://www.nps.gov/subjects/bears/brown-bears.htm

| The page says | The source says |
| :--- | :--- |
| whitebark pine seeds | In the fall, whitebark pine seeds are a preferred food for grizzly bears |
| elk calves, ground squirrels, and spawning trout | prey on vulnerable animals such as elk calves and spawning trout (note: ground squirrels: adw-ursus-arctos 'also dig mice, ground squirrels, marmots, and other fossorial animals out of their burrows') |
| Whitebark pine seeds are a favorite fall food | In the fall, whitebark pine seeds are a preferred food for grizzly bears |
| grizzlies also prey on elk calves and spawning trout | They are effective predators and prey on vulnerable animals such as elk calves and spawning trout |

## Bear Identification. National Park Service.

https://www.nps.gov/articles/bear-identification.htm

| The page says | The source says |
| :--- | :--- |
| bears along the coast of Alaska are called brown bears, while the typically smaller inland bears, with little or no access to food from the sea, are called grizzlies | Those that live in coastal areas of Alaska are called brown bears, while typically inland bears that have limited or no access to marine-derived food resources are often smaller and called grizzlies. |
| which black bears lack | Distinctive shoulder hump. ... Shoulder lies level or flat with back/lacks shoulder hump. (note: first fragment is the brown/grizzly bear, second the American black bear, in the page's side-by-side list) |

## Brown Bear. San Diego Zoo Wildlife Alliance.

https://animals.sandiegozoo.org/animals/brown-bear

| The page says | The source says |
| :--- | :--- |
| The most distinctive shoulder hump of any brown bear | grizzly bears have the most distinctive hump of all |
| roots, insects | Bears dig for roots, tubers, and insects |
| San Diego Zoo Wildlife Alliance says the coastal bears tend to be the largest, from eating fat-rich salmon every summer | Bears found in parts of coastal Alaska are called Kodiak or Alaskan brown bears and tend to be the largest. This is from eating salmon rich in fat every summer. |
| despite its reputation the grizzly is one of the smallest brown bear subspecies | Despite its "large" reputation, the grizzly bear is one of the smallest of the brown bear subspecies. |
| Grizzlies carry a large hump of muscle on their shoulders | Brown bears have a large hump of muscle on top of their shoulders |
| San Diego Zoo Wildlife Alliance says grizzlies have the most distinctive hump of any brown bear | grizzly bears have the most distinctive hump of all |
| dig for roots and insects | Bears dig for roots, tubers, and insects |
| A large hump of muscle on top of the shoulders | Brown bears have a large hump of muscle on top of their shoulders |
| San Diego Zoo Wildlife Alliance says all brown bears have one, and grizzlies have the most distinctive hump of all | Brown bears have a large hump of muscle on top of their shoulders, and grizzly bears have the most distinctive hump of all. |
| Their great front claws make brown bears powerful diggers | Their great front claws make all brown bears powerful diggers. |

## Greater Yellowstone Grizzly Bear and Army Cutworm Moths. Draper Natural History Museum, Buffalo Bill Center of the West.

https://centerofthewest.org/2014/04/01/greater-yellowstone-grizzly-bear-army-cutworm-moths/

| The page says | The source says |
| :--- | :--- |
| Army cutworm moths | A key food source in mid – late summer is the army cutworm moth. |
| hundreds of thousands of them migrate into the Rocky Mountains each year and rest under rocks in high boulder fields, and a single grizzly may eat more than 40,000 of them in one day | Each year, many hundreds of thousands of moths migrate from lowlands as much as 300 miles east of the Yellowstone to feed on the nectar of alpine wildflowers high in the Rocky Mountains. They feed at night and rest during the day under rocks in large boulder fields ... A grizzly bear may eat more than 40,000 moths in a single day. |
| A moth that migrates by the hundreds of thousands up into the Rocky Mountains each year to feed on alpine wildflowers, then rests by day under rocks in high boulder fields | Each year, many hundreds of thousands of moths migrate from lowlands as much as 300 miles east of the Yellowstone to feed on the nectar of alpine wildflowers high in the Rocky Mountains. They feed at night and rest during the day under rocks in large boulder fields |
| grizzlies comb those boulder fields, turning over rocks and scooping up dozens of moths at a time, and a single bear may eat more than 40,000 moths in one day | Both grizzly and black bears exploit this rich food source by combing through high mountain boulder fields, turning over rocks and scooping up dozens of moths at a time. A grizzly bear may eat more than 40,000 moths in a single day. |
| a bear that combs a boulder field turning over rock after rock, scooping up dozens of moths at a time | Both grizzly and black bears exploit this rich food source by combing through high mountain boulder fields, turning over rocks and scooping up dozens of moths at a time. (note: vibe.reason; the repeated flip-and-scoop is the loop the cycling guitar figures match) |
| can eat more than 40,000 of them in a single day | A grizzly bear may eat more than 40,000 moths in a single day. (note: vibe.reason) |

## Evans et al. (2016). Drivers of hibernation in the brown bear. Frontiers in Zoology.

https://doi.org/10.1186/s12983-016-0140-6

| The page says | The source says |
| :--- | :--- |
| A study that tracked brown bears in Sweden, the same species as the grizzly | physiological parameters of brown bears in Sweden (note: same species: the grizzly is a brown bear subspecies (sandiegozoo-brown-bear)) |
| they entered their dens once snow arrived and the air reached freezing | Bears entered the den when snow arrived and when ambient temperature reached 0 °C. |
| their body temperature began rising about two months before they left, driven by the outside air temperature | the unexpected early rise in T b (two months before den exit) was driven by T A |
| A study that tracked wild brown bears in Sweden | physiological parameters of brown bears in Sweden |
| found they entered their dens once snow arrived and the air temperature reached freezing | Bears entered the den when snow arrived and when ambient temperature reached 0 °C. |
| Their body temperature then began rising about two months before they left the den, driven by the outside air temperature | the unexpected early rise in T b (two months before den exit) was driven by T A |