Natural Histories

photograph of a Sunda Pangolin

Kodiak Bear, Alaskan Grizzly Bear, American Brown Bear

Ursus arctos


The brown bear is one of the largest living carnivores ranging from 1-2.8 meters long from head to rump (standing taller than 8 feet when the lengths of their legs are included). They can weigh between 80 to more than 600kg, males weighing about 10% more than females. Northern populations weigh much less, such as the Yukon brown bears weighing only 140kg. The fur of this species is dark brown, varying from cream to almost black. Rocky Mountain populations have long fur along the shoulders and back that is frosted with white coloring. This species is very strong (capable of killing a cow with one blow) and have very good endurance (outrun a horse or out swim an Olympian).


This species can be found in Alaska and Western Canada of North America. Many of the populations in Sierra Nevada and the southern Rockies are very sparse. Brown bears can live in various habitats including desert edges, high mountain forests and ice fields. They prefer the open areas of the tundra, alpine meadows and coastlines. This species used to be common on the Great Plains but European settlers diminished that population. European populations of brown bear prefer mountain woodlands and the Siberian populations of brown bear live in forests. This species requires some area of dense cover for shelter.

Feeding behavior and diet:

These omnivores consume many foods that are available with each season. They eat many grasses, sedges, roots, moss, and bulbs. Fruits, nuts, berries, and tubers are eaten in summer and fall. This species will dig insects, fungi, mice, ground squirrels, marmots from their burrows underground. Some populations are particularly carnivorous; hunting larger animals such as elk, moose and mountain sheep. A favorite of this species is hunting vulnerable trout and salmon that breed in the freshwater streams in the summer.


The estrus of a female brown bear lasts from 10-30 days; a male may fight with other males and guard a female for 3 weeks. Breeding occurs between May and July. After fertilization there is a period of delayed implantation for 5 months (typically in November) until the female has entered her winter sleep. After a 6-8 week gestation, 2-3 cubs are born between January and March while the female is still sleeping in hibernation. Females that have given birth will not ovulate for another 3-4 years. The mother brown bear lactates for 18-30 months even after her cubs are eating other foods. Cubs begin eating solid foods at 5 months old. They remain with their mother until their second –fourth spring. This species reaches sexual maturity between 4-6 years old but do not reach adult size until they are 10-11 years old.

Months and Times of Activity

Individuals can be found active at all parts of the day. Foraging typically occurs in the morning and evening and then the bears rest in dense cover during the day. They move seasonally, travelling hundreds of kilometers during the fall to reach areas with more food. From October- December the brown bear begins a period of inactivity and they do not resume activity until March or May. During this period the brown bear is in a deep sleep and its body temperature lowers. Southern populations may only have a brief or even non-existent period of inactivity.

Special Features, Stories, Relationships

  • The Rocky Mountain populations have long hairs on the shoulders and back with white tips, giving a “grizzled” appearance, and thus the name “grizzly bear”.
  • Brown bears are not “true hibernators” because they can be easily aroused from their winter sleep.
  • To read legends of this animal go to:
  • Children’s book featuring this animal: Mama Grizzly Bear by Margot Finke


Ballenger, L. 2002. "Ursus arctos" (On-line), Animal Diversity Web. Accessed November 04, 2014 at