Friday, February 1, 2013

Science Week 17: Great Bears of the Forest and Ice Floes

Except for opossum babies, no other mammal infants are as tiny in comparison to their mother as the bear infants. Born during the mother's winter hibernation, they may weigh as little as 1/200th of her weight. In the dark, cold den, the small rat-sized cubs are nearly lost in the dense fur of their mother. Hairless and blind, they snuggle contentedly into the shaggy folds of the mothers abdomen, where hidden milk glands allow for warm, comfortable nursing.

photo credit: Drive to Nature blog

Bears are mostly created for forest and mountain regions. In the spring bears graze like cattle on the new tender shoots and grasses. Later in the season, they use their strong shoulders, and powerful claws, to rip open rotting logs to lick up ants, beetle grubs, termites, and many other insects. Digging into ground burrows, they find chipmunks, marmots, moles, mice, ground squirrels, and lemmings. Crickets, grasshoppers, birds and their legs, snakes, frogs and toads, acorns, fruits, and wild honey, keep these big mammals well nourished.

Black Bear
photo credit: Bears of The World

The black bear is the smallest and most common of the American bears, and like other bears, it travels alone except for when still being cared for by its mother as a young cub. The same trails through forests and thickets will be followed for 50 years or more. Along these trails, bears will stand on their hind legs and rub their backs against the bark of trees. They bite it until it shreds loose in places, where pitch oozes out and sticks their hair to the trees. The next bear on the trail will do the same thing, leaving his scent behind for the next trail walker.

Grizzly Bear

Next in size to the widespread black bear is the grizzly. Originally found in the western part of North America, from Alaska to central Mexico, and east to Minnesota, there are now very few south of the Canadian border except in protected wildlife park areas.

The grizzly's diet is roughly 80-90% vegetation, though they come down to meet the salmon that run up-river from the sea. As the salmon swim up-river, the bear will knock it out of the water with a blow from its paw. When injured or attacked, the grizzly will react fearlessly.  It can run as fast as a horse, and a blow from its paw will crush or break the bones of even a huge bison.

Grizzly Bears, Bears of the World

File:Bear Square.JPG
photo credit: Wikipedia

The brown bear, also known as The Alaskan Brown Bear or Kodiak Bear is the largest of all bear species. Like the grizzly, it has its own set of trails along the rivers of British Columbia and southern Alaska. As the salmon swim up the river by the thousands, the big brown bears have a feast. After spawning, the salmon die and float down-stream, sooner or later coming to rest against a rock or sandbar. The great bears enjoy eating carrion, so the smelly dead heaps of fish are quickly removed and the riversides become clean in short order.

Brown Bears, Bears of the World
Brown bears, Alaska Dept. of Fish & Game be sure to check all the tabs below the article for more information

Brown bears are larger than black bears with male grizzly bears standing about 7 feet tall and generally weighing from 200 to 600 pounds. There have been some male bears that have weighed more than 800 pounds. Females are smaller, usually weighing between 200 and 400 pounds. Generally remaining on all fours, when a grizzly does stand, it is commonly perceived to be a threatening pose however they are just simply curious or surveying their surroundings.
Despite being categorized as ‘black bears' and ‘brown bears' to make a distinction, color is never an indicator of species. Both black and brown bears can range from almost white to blonde to pure black and many color phases in between depending on age, sex and season.
The main differences between the black bear and brown bear, is that the brown bear has a rather concave face, high-humped shoulders, and long, curved claws. The grizzly's thick fur, which varies from light brown to nearly black, sometimes looks frosty-looking, hence the name "grizzly," or the less common "silvertip."
Furthermore, the grizzly has more rounded shorter ears. Nevertheless, you cannot pin point one characteristic to distinguish between a grizzly and black bear, it is a combination of characteristics that will help you identify the bear specifically. Each may have a similar-colored coat, a less-than-concave face and small or large shoulder humps.
~~via Brown

File:Polar Bear - Alaska.jpg
photo credit: Wikipedia

The polar bear is the monarch of the arctic ice pack. On snow covered floes, these great bears will drift for hundreds of miles in the Arctic ocean, the Atlantic ocean, or through the Bering Strait into the Bearing Sea. They may swim 15-20 miles out to an iceberg in search of their most important food source, seals. When the seals are scarce, they will live on carrion. A sudden freeze may strand a white whale or a narwhal inside a little bay that later becomes so small the creature cannot breath adequately. A polar bear may kill even a whale that is 15 feet long. The powerful carnivore is able to drag an 800-pound animal out onto the ice. A large dead whale will provide food for bears, arctic foxes, gulls, and ravens all winter.
Fast Facts
  • Size
  • Males: 600–1200 lbs. 8–10 ft.; Females: 400–700 lbs.
  • Lifespan
  • 25 years
  • Distribution/Range
  • Circumpolar, northern hemisphere only
  • Diet
  • Ringed seals, bearded seals, walruses, beluga whales
  • Predators
  • Male polar bears, and Alaska Native hunters
  • Reproduction
  • 2 cubs once every 3 years

Bears lapbook, Homeschool Share, another one here, heared toward Preschool-1st
Polar Animals lapbook, Homeschool Share
Polar Bear Squidoo Lens
Polar Bear lapbook at The Schroeder Page blog
Polar Bears, Early and Modern at Bears of The World

Bears like to clown around and play like most animals. A polar bear will rock themselves on a drifting ice floe or slide down a slanting, slippery glacier side. They have been seen walking along a narrow wall of ice with an almost vertical glacier below, then jump onto the slick surface of the glacier and whiz itself down, without trying to slow themselves down, until they reach the edge of the glacier. There, with a sheer 50 ft drop, they will sail into the air and plunge into the water below. Sometimes they will sit near an icy slope and, just as you or I would, rock themselves back and forth to get started sliding downward. 

bear track account, Wilderness College

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