American Black Bear Size

American black bears vary in size depending on sex, food availability and quality, and other factors. Male black bears may grow 20 to 60 percent larger than females. Weight of black bears vary with age, sex, season and health. Seasonal variation in weight is very pronounced: in autumn, their pre-den weight tends to be 30% higher than in spring, when black bears emerge from their dens. Black bears on the East coast tend to be heavier than the black beas from the West coast. Adult males usually weight between 125 and 550 lb, while females weigh 33% less at 90–275 lb. The largest subspecies on average is U. americanus carlottae of the Queen Charlotte Islands and Alaska. The biggest wild American Black Bear ever recorded was a male from North Carolina, shot in 1998, that weighed 400 kg (880 lb). Adults are 4–6 ft in length, and 2.5–3 ft in shoulder height.[32] The North American Bear Center, located in Ely, Minnesota, is home to the world's largest captive male and female black bears. Ted, the male, weighed 950–1,000 lb (430–450 kg) in the fall of 2006. , the female, weighed 555.5 lb (252.0 kg) in the fall of 2007.

American Black Bear Build

American black bear skull is wide, with narrow muzzles and large jaw hinges. Females tend to have more slender and pointed faces than males. Their claws are typically black or grayish brown. Claws are short and rounded, being thick at the base and tapering to a point. Claws from both hands and legs are the same length, , though the foreclaws tend to be more sharply curved. Their hind legs are longer than the Asian black bear hind legs. The tail is usually 4.8 inches (12 cm) long. The ears are small and rounded, and are set well back on the head. The soles of the feet are black or brownish, and are naked, leathery and deeply wrinkled. Black bears are highly dexterous, being capable of opening screw-top jars and manipulating door latches. They also have great physical strength, having been known to turn over flat-shaped rocks weighing 310 to 325 pounds (140 to 147 kg) by flipping them over with a single foreleg.[32] They move in a graceful, rhythmic and surefooted way and can run at speeds of 25–30 mph (40–50 km/h).[33] Black bears have good eyesight, and have been proven experimentally to be able to learn visual discrimination tasks based on color faster than chimpanzees and as fast as dogs. They are also capable of rapidly learning to distinguish different shapes, such as small triangles, circles and squares.

American Black Bear Hybrids

American black bears are reproductive compatible with several other species of bears, and have often produce hybrid offspring. According to Jack Hanna's Monkeys on the Interstate, a bear captured in Sanford, Florida thought to be a offspring of escaped female Asian black bear and American black bear. In 1859, a black bear and a Eurasian brown bear were bred together in the London Zoological Gardens, but the three cubs did not reach maturity. In The Variation of Animals and Plants under Domestication Charles Darwin noted:

In the ninth-year report has found that the bears are seen in the Zoological Gardens to couple freely, but previously to 1848 most had rarely conceived In the Reports published since this date three species have produced young (hybrids in one case).

A huge black bear was shot in Autumn 1986 in Michigan, for which some thought was a hybrid of black bear and grizzly bear, due to its unusually large size and its proportionately larger braincase and skull. DNA tests failed to show whether it is a black bear or grizzly bear.

American Black Bear Subspecies

Sub-Species Name	Common Name	Distribution	Description
Ursus americanus altifrontalis		Found in the Pacific Northwest coast from central British Columbia through northern California and inland to the tip of northern Idaho and British Columbia
Ursus americanus amblyceps		Native to Colorado, New Mexico, west Texas, the eastern half of Arizona into northern Mexico; southeastern Utah
Ursus americanus americanus		Found in eastern Montana to the Atlantic coast; from Alaska south and east through Canada to the Atlantic and south to Texas. Thought to be increasing in some regions.
Ursus americanus californiensis		Found in the mountain ranges of Southern California, north through the Central Valley to southern Oregon
Ursus americanus carlottae	Haida Gwaii Black Bear	Haida Gwaii/Queen Charlotte Islands and Alaska	Generally larger than its mainland counterparts with a huge skull and molars, and is only found as a black color phase
Ursus americanus cinnamomum	Cinnamon Bear	Idaho, western Montana, and Wyoming, eastern Washington and Oregon, northeastern Utah	Has brown or red-brown fur, reminiscent of cinnamon.
Ursus americanus emmonsii		southeastern Alaska. Stable.	Distinguished by the fur of its flanks being silvery gray with a blue lustre
Ursus americanus eremicus		northeastern Mexico. Endangered.
Ursus americanus floridanus	Florida Black Bear	Florida, southern Georgia, and Alabama. Threatened in Florida as the Florida Black Bear (state list).	Has a light brown nose, and shiny black fur. A white chest patch is also common. An average male weighs 299 pounds (136 kg)
Ursus americanus hamiltoni	Newfoundland Black Bear	Newfoundland	Generally bigger than its mainland relatives, ranging in size from 90 to 270 kg and averaging 135 kg. It also has one of the longest hibernation periods of any bear in North America
Ursus americanus kermodei	Kermode Bear, Spirit Bear	Central coast of British Columbia	Has white fur due to a rare genetic trait
Ursus americanus luteolus	Louisiana Black Bear	Eastern Texas, Louisiana, southern Mississippi. Threatened (federal list).	A subspecies with a relatively long, narrow, and flat skull, and proportionately large molar teeth
Ursus americanus machetes		North-central Mexico
Ursus americanus perniger		Kenai Peninsula, Alaska
Ursus americanus pugnax		Alexander Archipelago, Alaska
Ursus americanus vancouveri		Vancouver Island, British Columbia

Taxonomy and evolution

Although they all live in North America, American black bears, brown bears, and polar bears are not closely related, genetic studies have revealed that they split from a common ancestor before about 5,05 million years. Both American and Asiatic black bears are considered sister taxa, and are more related to each other than other bears species.

A small primitive bear called Ursus abstrusus is the oldest known North American fossil member of the genus Ursus, dated to 4.95 millions years ago. This suggests that U. abstrusus may be the direct ancestor of the American black bear, which evolved in North America. Although Wolverton and Lyman still consider U. vitabilis an "apparent precursor to modern black bears", it has also placed within U. americanus.

Ancestor of the American black bear and the Asian black bear diverged from sun bears 4.58 million years ago. Then the American black bear separated from the Asian before about 4.08 million years ago. The earliest fossils of American black bears, which are located in Port Kennedy, Pennsylvania, greatly resemble the Asiatic species, though later specimens grew to sizes comparable to grizzlies. From the Holocene to present, American black bears seem to have shrunk in size, but this was rejected due to issues of aging of the fossil samples.

American black bear lived in the same period as as short-faced bears (Arctodus simus and A. pristinus) and the Florida spectacled bear (Tremarctos floridanus). These Tremarctine bears evolved from bears that had emigrated from Asia to North America 7–8 millions years ago. The short-faced bears are thought to have been heavily carnivorous and the FL spectacled bear more herbivorous, while the American black bears remained arboreal omnivores, like their Asian ancestors. The black bear's generalist behavior allowed it to exploit a wider variety of foods and has been given as a reason why of these 3 genera, is the only survived climatic and vegetative changes during and after the Ice Age, while others more specialized North American predators extinct. However, both Arctodus and Tremarctos had survived several other ice ages. After these prehistoric Ursids went extinct during the last glacial period 10,000 years ago, black bears are probably the only bears in much of North America, while brown bears did not come into the rest of continent.