All bears belong to the taxonomic family ursidae, which
is comprised of all eight extant species of bear. Ursidae
is divided into three subfamilies, which are ursinae,
tremarctinae, and ailuropodinae. Ursinae is the largest
of these subfamilies, containing American black bears,
brown bears (of which grizzly bears are a subspecies),
polar bears, sloth bears, sun bears, and Asian black
bears.The subfamily tremarctinae, on the other hand,
contains only the spectacled bear. Ailuropodinae also
contains only one extant species, the giant panda.
Even though few species of them exist, and most are
endangered, bears are very widespread, being found in
Europe, Asia, North America, and South America. The
most widespread species of bear is the brown bear, which
can be found throughout the former three continents.
The bear species residing in the narrowest range is
the spectacled bear, which populates only the Andean
region of South America, and is the only species of
bear found on that continent. Polar bears are found
only on the Arctic Sea, and American black bears are
confined to North America; the remaining four species
reside in Asia.
Bears tend to inhabit forests, with the exception of
polar bears, which live at sea and on sea ice and Arctic
archipelagos. Some bears, especially the brown bear,
may be found in alpine shrubland or tundra, in which
they may reside either seasonally or permanently.
When the climate of many bears' habitats becomes cold
and food becomes scarce, these species of bear retreat
to their dens and enter a deep state of rest. This habit
is colloquially known as hibernation, though it is not
a true hibernation; bears' breathing, heart rate, and
metabolic rates slow only a little bit, their body temperatures
do not drop considerably, and they may occasionally
rouse from this state, while true hibernators experience
more significant changes to their bodily processes and
do not rouse from hibernation.
Bears are large creatures with heavy bodies, long sharp
claws, relatively short legs, and large heads with long,
canine teeth. They range in weight across species, with
the smallest species, the sun bear, weighing between
100 and 140 lb on average, and the largest species,
the polar bear, weighing an average of 850-900 lb. The
largest individuals, however, are often brown bears,
with some subspecies weighing up to 1,180 lb on average.
Bears are quadrupedal, meaning they walk on four legs,
but can stand on two legs and sit as humans do.
Despite their reputation for being voracious carnivores,
bears, with the exception of polar bears and giant pandas,
are usually omnivorous. (Polar bears are carnivores
relying a diet of mostly on marine mammals, while giant
pandas eat mostly bamboo.) Bears' diets are determined
largely by their environment, as they will feed on any
food source that is available to them. They use their
exceptional sense of smell to locate food and prey.
Bears are predominantly predators and tend not to be
prey; the only routine natural predator of adult bears
is the tiger, which inhabits only Asia.
About the Author
Jacob Maddox manages content for Wildlife Animals http://www.wildlife-animals.com
an educational wildlife and animal website.