Glacier bear

Glacier bear
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Ursidae
Genus: Ursus
Species: U. americanus
Subspecies: U. a. emmonsii
Trinomial name
Ursus americanus emmonsii

The glacier bear (Ursus americanus emmonsii), sometimes referred to as the blue bear, is a subspecies of American black bear with silver-blue or gray hair endemic to Southeast Alaska. There is little scientific knowledge of their total extent and the cause of their unique coloration. Most of the other black bears in Southeast Alaska are listed under the subspecies Ursus americanus pugnax.[1][2]

Unique features

Ursus americanus emmonsii

The chief feature distinguishing the glacier bear from other black bears is its pelage (hair coloration), which ranges from silvery blue to gray. This variation can be seen on individual bears that are often lighter on their backs and shoulders, with their legs and belly being much darker or even black. Currently there is no evidence to determine if this coloration is the only physical characteristic that is unique to the glacier bear compared to other black bears.

Habitat

The glacier bear's habitat ranges from Prince William Sound to Glacier Bay in Southeast Alaska, with a few sightings as far east as Juneau, Alaska and the Taku River.[3][4] This region includes Glacier Bay National Park and portions of Tongass National Forest, a temperate rainforest preserve.[5][6][7]

Glacier bears share most of the characteristics of black bears such as their habitat preferences, food sources, size and reproductive cycles. They prefer forest with thick understory and landscapes with lots of vegetation, but can be found in urban populated areas. The glacier bear habitat is dependent upon food source availability, and they will move between forest, meadows, streams and mountains in search of food and shelter. Black bears in general are very capable climbers and can use trees as a place of protection and refuge. Glacier bears will move into their dens in early winter, which can be an overturned tree, a rock ledge or a cave.

Diet

Glacier bears, like all other black bears, are omnivores with their diets varying depending on the food source available during the season and the location.[8] Their diet includes young shoots and roots in early spring. During the summer months in Alaska, the glacier bear will eat the abundant Pacific salmon spawning in the streams. In some areas moose and deer are a food source for black bears. During the fall the bears will eat the starchy roots of ground cones and variety of berries found in Alaska such as blueberries, salmonberries, raspberries, and cranberries.

Reproduction

Breeding habits are much like any other black bear. The glacier bear will normally will have their first litter by 3–5 years of age. This breeding period will take place in June through July. Gestation last 235 days and cubs will be born in January to early February.[8] Because of the increasing range of all subspecies of black bear since the last glacier maximum, there is interbreeding taking place. For this reason it is possible to see a black in color bear give birth to a bear with the glacier bears' pelage and vice versa.

Research

Very little is known about this rare color variation and so there are some potential threats that could become an issue for the glacier bear. Some of these threats are over-harvesting and gene swamping. There is no current indication that these bears are being over-harvested, but due to coloration they could become a target for sport hunting. Currently there are no population projections due to the lack of genetic understanding. With the interbreeding capabilities of other black bears with different pelage, determining the future distinctive color variation and population density may become even more complicated. There has also been speculation that the glacier bear had its origins in hybrids between black bears and grizzlies.[9] Further research will need to be done to determine any genetic differences and if glacial refugia may have contributed to lineages and pelage coloration.

References

  1. ↑ MacDonald, S.O. and Cook, J.A. (2007) Mammals and amphibians of Southeast Alaska. The Museum of Southwestern Biology, The University of New Mexico, Albuquerque, NM 87131-0001.
  2. ↑ Schoen, J and Peacock, L. (2007) "Black Bear" in J Schoen and E Dovichin (eds.) The coastal forest and mountains ecoregion of southeastern Alaska and the Tongass National Forest. Audubon Alaska and The Nature Conservancy, 715 L Street, Anchorage, Alaska
  3. ↑ http://www.pbs.org/wnet/nature/episodes/bears-of-the-last-frontier/hour-two-the-road-north/black-bear-fact-sheet/7012/
  4. ↑ http://bear.org/website/index.php?option=com_content&view=article&id=35:classification-of-black-bears&catid=15&Itemid=38
  5. ↑ Threatened Wildlife of the United States, U.S. Bureau of Sport Fisheries and Wildlife, Washington, for sale by the Supt. of Docs., U.S. Govt. Print. Office.
  6. ↑ MacDonald, S.O. and Cook, J.A. (2007) Mammals and amphibians of Southeast Alaska. The Museum of Southwestern Biology, The University of New Mexico, Albuquerque, NM 87131-0001.
  7. ↑ Schoen, J and Peacock, L. (2007) "Black Bear" in J Schoen and E Dovichin (eds.) The coastal forest and mountains ecoregion of southeastern Alaska and the Tongass National Forest. Audubon Alaska and The Nature Conservancy, 715 L Street, Anchorage, Alaska
  8. ↑ 8.0 8.1 Powell, Roger A., Zimmerman, John Wayne and Seaman, David Erran (1997) Ecology and behaviour of North American black bears: home ranges, habitat, and social organization. Vol. 4. Springer, ISBN 0412788306.
  9. ↑ http://www.thegreatbearshow.com/Bear_Facts.html