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INTRODUCTION:
Where did the Bear's 
came from ?

:Contents:
 
 
Where Did the Bear's came from?
The Rise and Downfall of the "Third Bear"
Homing Instinct
Hibernation
Our Surviving Bear's
The Body of the Bear's
Bear Feet 
Bear Teeth and Birthdays <"Beardays">
Food Strategies
 
 
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Where Did the Bear's Came from:
 
 

    Facts about the beginnings of the  bear are quite undetermined.  Apparently, about 30 to 40 million years ago, during the early portion of the Oligocene epoch, bears began to evolve from a family of small, carnivorous, tree climbing mammals called miacids. Coyotes, wolves, foxes, raccoons, and dogs are also thought to have evolved from this ancestral stock.  Very early in the history of  the miacids developed special teeth for piercing and tearing flesh the canine teeth.  The early carnivores developed other special teeth called carnassials.  The last premolar I the upper jaw and the first molar in the lower jaw were modified to ac like scissors, shearing meat into easily swallowed chunks.
  At first, the brains of these carnivores were small, perhaps because those early herbivores on which they fed could caught without much trouble.
  Meat eating became a highly successful occupation for carnivores, and they quickly radiated into three main branches: the dog, the cat, and seal families.  The first true bears evolved from the tribe of heavy bear like dogs that existed in North America during the late Oligocene epoch, some 27 million years ago.
  According to some researchers, the oldest known bear, Ursavus elemensis, was about the size of a fox terrier.  It lived about 20 million years ago in a subtropical Europe.  Bears came into their own about 6 million years ago and quickly evolved into numerous forms.  Some grew to enormous size.  Then, because of widespread changes, probably climatic, nine genera and numerous bear species became extinct.  Somewhere during this time our modern line of bears developed from a little bear known as Protursus , which also died out in time.

 
 
 
The Rise and Downfall of the Third Bear
 About 2.5 million years ago the first of the genus Ursus (Latin for bear) appeared.  From its European descendants came the Etruscan bear, Ursus etruscus, which later separated  into three distinct lines.  Two of these lines were found in Asia, and is thought that they lead to today's brown bears and black bears.  The third line, now extinct, lived in Europe, and is known as the cave bear, ursus spelaus.  Cave bears were contemporaries of early humans, who probably hunted them for food.  Fossil remains of cave bears span the period from 30,000 or 40,000 (maybe even 50,000) years to  about 10,000 years ago.
Just why the cave bear died out is a subject of great speculation among paleontologists.  Some assert that the bar perished of its own "self domestication" from prolonged internment during the long Ice Age winters.  When large predators are kept for many years in the confinement of cages, peculiar diseases of the spinal column develop.  These include inflammations, fusing, and atrophy.  An extraordinary large number of cave bears remains are from the diseased or physically degenerated bears.
   Also extraordinary are the numbers of cave bear skeletons that have been discovered.  The most impressive find was in dragon's cave at Mixnitz in Austria.  Here the skeletal remains of over 30,000 animals were piled up.  How did they all get in there ?  No one really knows .  A stone chest filled with bear skulls, uncovered in Drachenloch Cave in the Swiss Alps, suggests the possibility that the cave bear may have been on e of man's first hunting trophies.  In a cave near Erd, Hungary lie the bones of more than 500 cave bears  that were  supposedly killed by Neanderthal man.  Dating by carbon 14 methods indicates that the bones remains whose demise seems to have been linked to humans.  Did early Europeans cause, or at least hasten, the extinction of the cave bars/ Its probable.  Many cave bear skeletons still retain traces of ax blows.
  Whatever the reasons for its demise, the cave bears is long gone.  The European   brown bear,   which took its place, is only a third the size of its Ice Age ancestors.
 

 
 

Homing Instinct
  If a bear is removed from its home range it will display an extraordinary homing instinct.  In  Michigan, an adult male black bear homed after being transplanted by air for a distance of 156 miles (251 km).  Twelve adult Alaskan brown bears returned  to their capture sites in an average of fifty-eight days.  They all had been transplanted over 125 miles (201 km) away.
 
 
Hibernation
  A bear’s instinct to den is an adaptation to life in places where winter conditions might otherwise threaten survival.  For some unknown reason, a few individuals of a hibernating species may remain active all winter even though no food maybe available.  Normally, the problems of reduced food supply, decreased mobility because of deep snow, and the increased energy costs of keeping warm are solved by denning and hibernation.
   Northern bears usually choose a low cave,  a hollow tree, or the shelter of a brush pile as a den site in which to hibernate.  Sometimes an earthen den is dug directly into the ground.  Often the den chamber is lined with dried grasses and leaves to make an insulated bed.
   Denning time generally coincides with the first inclement winter weather, although the disappearance of high-quality food determines the actual time of denning.  During late summer, bears  have been known to eat as much as 20,000 calories a day in a final effort to accumulate enough fat reserves for hibernation.  This is equivalent to a human eating thirty-eight banana splits or forty-two hamburgers a day.  Most zoo bears, when regularly fed throughout winter, do not den.
   During the last days before hibernation, some kinds of bears will eat certain indigestible materials—resinous plants and fibers—which form a mass in the rectum and plug the anus.  The function of the anal plug is not well understood.
   Biologists differ as to whether or not bears enter a state of true hibernation, but the controversy may be largely a matter of terminology.  Many smaller mammals, such as chipmunks and marmots, enter a deep sleep from which they cannot be easily aroused.  While they are dormant, their body temperature are considerably lower than normal.  A hibernating bear’s temperatures are considerably lower  than normal.  A hibernating bear’s temperature, in contrast, does not drop more than about 9 F 95 C) from its normal 87.8 to 99 F (31 to 37.4 C).  Bears can be easily awakened, but if undisturbed, they may sleep for as long as a month without changing position.
  Hibernating bears can remain in their dens from two and a half to seven months, depending on climate, without eating food, drinking water, urinating, or defecating.  Smaller mammals, however, must wake up periodically to eat and expel body wastes.
   Bears accomplish this amazing fast through their unique metabolic system.  During hibernation the water content of their blood remains at a constant level.  Minor losses of water are balanced by the breakdown of fat reserves.  Although a small amount of urea is continually formed, it is quickly degraded
by a refined system that recycles nitrogen and prevent toxic uremia.  Knowledge about these metabolic system is helping researchers to develop special diets for humans with kidney problems and diabetes.
   During winter hibernation a bear burns about 4,000 calories a day.  Although its heart rate drops to about eight bears per minute, compared to from forty to fifty beats per minute during summer sleep, its oxygen consumption rate may drop only about 50 percent of that of an active bear.  Bears also have been known to shiver in order to generate enough heat to keep warm during hibernation.
   When bears leave their dens in the springtime, it may take weeks before they resume their normal intake of ood.  Apparently, these metabolic adjustments of hibernation persist for some time after they have become active again.
 
 
 
Our Surviving Bears
  The world’s most recently evolved bear, the polar bear, is thought to have branched off the European ursus stock of brown bears about 100,000 years ago. Every continent except Australia has had or still has bears.  Today only eight species survive.  In some places their numbers have become so greatly reduced that forms of six species are now included in the International Union for the  Conservation of Nature (IUCN) red-list of endangered animals.
 
 
 
The Body of the Bear
 As a group, bears all look pretty much alike, varying in size and color but not in general shape. A comparison of skeletons reveals many similarities to dogs and wolves.  But unlike members of the dog family, bears grow to be quite large, more than 100 pounds (45kg) as adults.  Some reach massive sizes.
  Bears have heavily built bodies with relatively short legs, necks, and tails.
They have large heads with rounded ears and usually small eyes for so large an animal.  Unlike other carnivores, a bear’s lip are free from the gums, allowing them to be mobile and protrusible.  Their heavy pelts, padded by several inches of fat, often create the illusion of a slow and clumsy animal.  This is not so—a big brown bear can reach a speed of  35 or 40 mph (56 or 64 kmph.) for crashing blow from a forepaw.
   Most bears are unable to leap even a few feet off the ground.  Nearly all are expert climbers, however, and all bears are capable of swimmers.
 
 
 
Bear Feet
  The five toes of each broad foot are equipped with curving, non-retractable claws.  The claws are usually longer on the hind feet than on the front feet.  In spite of having claws instead of fingers, bears are very adept at manipulating objects with their front feet.  I have seen a big brown bear delicately turning a feather over and over in its paws.  The forepaws make useful digging instruments which are constantly employed as the bear forages for food.  Like humans, bears are plantigrade; they put their heel and foot down  flat on the ground when they walk. This flat-footed stance makes it easy for them to stand up on their hind legs.  When walking on all fours, bears turn their front feet inward in a pigeon-toed position.
 
 
 
Bear Teeth and Birthdays
  Bear’s teeth, though large  are not particularly specialized for meat eating.  They have pointed canines that help catch kill prey, but their premolars (carnassials) are no longer specialized for tearing meat.  Their molars are the heavy, crushing type of typical of plant eaters. 9More than 75% of most bears diet consist of plant material.)
   Wild bears may live more than thirty years. But a very old bear is unusual because of the heavy toll caused by hunting and other mortality factors.  Sometimes an entire bear population may be younger than ten years of age.  Generally speaking, a young population indicates a high deah rate among bears.
   Varying widths of annuli in the teeth indicate the history of the animals general health.  In a female’s teeth, for example, if the annuli are very close together, usually indicates that she had cubs and was lactating at the time the rings were formed.
 
 
 
Food Strategies
  Northern bears have a  terrific motivation to gain weight. Since much of their year is spent asleep in hibernation, they have only a short active period in which to find enough food to survive the winter.  Much of a bear’s waking time is spent solving the problem of getting food, the more nutritious the better.  For example, bear’s prefer to eat plants when they are at the peak of protein content -usually during pre-flowering or early flowering stages.
   If food becomes extremely abundant, such as during salmon run in Alaska, bears may become selective about what portions of the fish they eat.  Hungry bears will eat the entire salmon.  They prefer, however, to eat the eggs of the female salmon, which  are extremely rich in nutrition.  When  a bear catches a salmon it determines at once whether it is a male o a female.  If a salmon are plentiful, the bear will often abandon the males and resume fishing in hope of catching a female salmon.
  A bear normally spends its time in  a series of small areas where it can find food.  Collectively, these areas make up its home range.  It moves around within this range in order to take advantage of seasonal food sources.  The routes to and from these area of use are often called lanes.  Although bears will use human roads, 95 percen of their travel is off-road, particularly in swamps and forests.
 
 

 

 
 

by: John Froilan  Reyes