American black bear
The American black bear, or simply black bear, is a species of medium-sized bear which is endemic to North America. It is the continent's smallest and most widely distributed bear species. It is an omnivore, with a diet varying greatly depending on season and location. It typically lives in largely forested areas; it will leave forests in search of food and is sometimes attracted to human communities due to the immediate availability of food.
The International Union for Conservation of Nature lists the American black bear as a least-concern species because of its widespread distribution and a large population, estimated to be twice that of all other bear species combined. Along with the brown bear, it is one of the two modern bear species not considered by the IUCN to be globally threatened with extinction.
Taxonomy
The American black bear is not closely related to the brown bear or polar bear, though all three species are found in North America; genetic studies reveal that they split from a common ancestor 5.05 million years ago. American and Asian black bears are considered sister taxa and are more closely related to each other than to the other modern species of bears.Evolution
The ancestors of American black bears and Asian black bears diverged from sun bears 4.58 mya. The American black bear then split from the Asian black bear 4.08 mya. A small, primitive bear genus called protarctos is the oldest known North American fossil member of the genus Ursus, dated to 4.95 mya. This suggests that U. abstrusus may be the direct ancestor of the American black bear, which evolved in North America.The earliest American black bear fossils, from the Early Pleistocene of Port Kennedy, Pennsylvania, greatly resemble the Asian species, though later specimens grew to sizes comparable to grizzly bears. Once described as a precursor species, these specimens have been synonymized with U. americanus. The American black bear lived during the same period as the giant and lesser short-faced bears and the Florida spectacled bear. These tremarctine bears evolved from bears that had emigrated from Asia to the Americas 7–8 mya. The giant and lesser short-faced bears are thought to have been heavily carnivorous and the Florida spectacled bear more herbivorous, while the American black bears remained arboreal omnivores, like their Asian ancestors. From the Holocene to the present, American black bears seem to have shrunk in size, but this has been disputed because of problems with dating these fossil specimens.
The American black bear's generalist behavior allowed it to exploit a wider variety of foods and has been given as a reason why, of these three genera, it alone survived climate and vegetative changes through the last Ice Age while the other, more specialized North American predators became extinct. However, both Arctodus and Tremarctos had survived several other, previous ice ages. After these prehistoric ursids became extinct at the end of the Pleistocene, American black bears, brown bears and polar bears were the only remaining bears in North America.
Hybrids
American black bears are reproductively compatible with several other bear species and occasionally produce hybrid offspring. According to Jack Hanna's Monkeys on the Interstate, a bear captured in Sanford, Florida, was thought to have been the offspring of an escaped female Asian black bear and a male American black bear. In 1859, an American black bear and a Eurasian brown bear were bred together in the London Zoo, but the three cubs that were born died before they reached maturity. In The Variation of Animals and Plants Under Domestication, Charles Darwin noted:A bear shot in autumn 1986 in Michigan was thought by some to be an American black bear/grizzly bear hybrid, because of its unusually large size and its proportionately larger brain case and skull. DNA testing was unable to determine whether it was a large American black bear or a grizzly bear.
Subspecies
Sixteen subspecies are traditionally recognized; however, a 2015 genetic study did not support designating some of these, such as the Florida black bear, as distinct subspecies. Listed alphabetically according to subspecific name:Distribution and population
Historically, American black bears occupied the majority of North America's forested regions. Today, they are primarily limited to sparsely settled, forested areas. American black bears currently inhabit much of their original Canadian range, though they seldom occur in the southern farmlands of Alberta, Saskatchewan and Manitoba; they have been extirpated on Prince Edward Island since 1937. Surveys taken in the mid-1990s found the Canadian black bear population to be between 396,000 and 476,000 in seven provinces; this estimate excludes populations in New Brunswick, the Northwest Territories, Nova Scotia and Saskatchewan. All provinces indicated stable populations of American black bears over the 2000s.The current range in the United States is constant throughout most of the Northeast and within the Appalachian Mountains almost continuously from Maine to northern Georgia, the northern Midwest, the Rocky Mountain region, the West Coast and Alaska. However, it becomes increasingly fragmented or absent in other regions. Despite this, American black bears in those areas seem to have expanded their range in recent decades, such as with sightings in Ohio, Illinois, southern Indiana, and western Nebraska. Sightings of itinerant black bears in the Driftless Area of southeastern Minnesota, northeastern Iowa, and southwestern Wisconsin are common. In 2019, biologists with the Iowa Department of Natural Resources confirmed documentation of an American black bear living year-round in woodlands near the town of Decorah in northeastern Iowa, believed to be the first instance of a resident black bear in Iowa since the 1880s.
Surveys taken from 35 states in the early 1990s indicated that American black bear populations were either stable or increasing, except in Idaho and New Mexico. The population in the United States was estimated to range between 339,000 and 465,000 in 2011, though this estimate does not include data from Alaska, Idaho, South Dakota, Texas or Wyoming, whose populations were not recorded in the survey. In California there were an estimated 25,000-35,000 black bears in 2017, making it the largest population of the species in any of the 48 contiguous United States. In 2020 there were about 1,500 bears in Great Smoky Mountains National Park, where the population density is about two per square mile. In western North Carolina, the black bear population has dramatically increased from about 3,000 in the early 2000s to over 8,000 in the 2020s.
As of 1993, known black bear populations in Mexico existed in four areas, though knowledge on the distribution of populations outside those areas has not been updated since 1959. Mexico is the only country where the species is classified as "endangered".
Habitat
Throughout their range, habitats preferred by American black bears have a few shared characteristics. They are often found in areas with relatively inaccessible terrain, thick understory vegetation and large quantities of edible material. The adaptation to woodlands and thick vegetation in this species may have originally been because the bear evolved alongside larger, more aggressive bear species, such as the extinct giant short-faced bear and the grizzly bear, that monopolized more open habitats and the historic presence of larger predators, such as Smilodon and the American lion, that could have preyed on black bears. Although found in the largest numbers in wild, undisturbed areas and rural regions, American black bears can adapt to surviving in some numbers in peri-urban regions, as long as they contain easily accessible foods and some vegetative coverage.In most of the contiguous United States, American black bears today are usually found in heavily vegetated mountainous areas, from in elevation. For American black bears living in the American Southwest and Mexico, habitat usually consists of stands of chaparral and Pinyon–juniper woodlands. In this region, bears occasionally move to more open areas to feed on prickly pear cactus. At least two distinct, prime habitat types are inhabited in the Southeastern United States. American black bears in the southern Appalachian Mountains survive in predominantly oak-hickory and mixed mesophytic forests. In the coastal areas of the southeast, bears inhabit a mixture of flatwoods, bays and swampy hardwood sites.
In the northeastern part of the range, prime habitat consists of a forest canopy of hardwoods such as beech, maple, birch and coniferous species. Corn crops and oak-hickory mast are also common sources of food in some sections of the northeast; small, thick swampy areas provide excellent refuge cover largely in stands of white cedar. Along the Pacific coast, redwood, Sitka spruce and hemlocks predominate as overstory cover. Within these northern forest types are early successional areas important for American black bears, such as fields of brush, wet and dry meadows, high tidelands, riparian areas and a variety of mast-producing hardwood species. The spruce-fir forest dominates much of the range of the American black bear in the Rockies. Important non-forested areas here are wet meadows, riparian areas, avalanche chutes, roadsides, burns, sidehill parks and subalpine ridgetops.
In areas where human development is relatively low, such as stretches of Canada and Alaska, American black bears tend to be found more regularly in lowland regions. In parts of eastern Canada, especially Labrador, American black bears have adapted exclusively to semi-open areas that are more typical habitat in North America for brown bears.
Description
Build
The skulls of American black bears are broad, with narrow muzzles and large jaw hinges. In Virginia, the length of adult bear skulls was found to average. Across its range, the longest reported skull measured from. Sexual dimorphism can be seen in the tendency for females to have slenderer and more pointed faces, and conversely, for larger cheek teeth in males.Their claws are short and curved, being thickest at the base then tapering to a point, and most often black or grayish-brown in color. Claws from both hind and front legs are almost identical in length, though the curvature of foreclaws tends to be greater. The paws of the species are relatively large, with the forepaws measuring by and the hindpaws by, which is proportionately larger than other medium-sized bear species, but markedly smaller than those of large adult brown bears, and even more so, polar bears. The soles of the feet are black or brownish and are naked, leathery and deeply wrinkled.
The hind legs are relatively longer than those of Asian black bears. The typically small tail is. The ears are small and rounded, as well as being set well back on the head.
American black bears are highly dexterous, being capable of opening screw cap containers and manipulating door latches. They also have great physical strength; a bear weighing was observed flipping over flat rocks weighing with a single foreleg. They move with a rhythmic, sure-footed gait and can run at speeds of up to. American black bears have good eyesight and have been proven experimentally to be able to learn visual color discrimination tasks faster than chimpanzees and just as fast as domestic dogs. They are also capable of rapidly learning to distinguish different shapes, such as small triangles, circles and squares.