The Asian black bear (Ursus thibetanus), also known as the Moon bear or White-chested bear is a medium-sized species of bear, largely adapted for arboreal life, which occurs through much of southern Asia, northeastern China, the Russian far east and Japan.

It is classed by the IUCN as a vulnerable species, mostly due to deforestation and active hunting for its body parts.

The species is morphologically very similar to some prehistoric bears, and is thought by some scientists to be the ancestor of other extant bear species.

Though largely herbivorous, Asian black bears can be very aggressive toward humans, and have frequently attacked people without provocation. The species was described by Rudyard Kipling as "the most bizarre of the ursine species.

Biologically and morphologically, Asian black bears represent the beginning of the arboreal specialisations attained by sloth bears and Sun bears, though these traits are not as maximally attained in Asian black bears.

Asian black bears have karotypes nearly identical to those of the five other ursine bears, and, as is typical in the genus.

They have 74 chromosomes. From an evolutionary perspective, Asian black bears are the least changed of Old world bears, with certain scientists arguing that it is likely that all other lineages of ursine bear stem from this species.

Asian black bears are close relatives to American black bears, with which they share a European common ancestor which is thought to have diverged 3 million years ago, though genetic evidence is inconclusive.

Both American and Asiatic species are considered sister taxa, and are more closely related to each other than other species of bear.

The earliest American black bear fossils, which were located in Port Kennedy, Pennsylvania, greatly resemble the Asiatic species The first DNA study undertaken on Asian black bears suggested that the species arose after the American black bears, while a second study could not statistically resolve the branching order of sloth bears and the two black species, suggesting that these three species underwent a rapid radiation event.

A third study suggested that American black bears and Asian black bears diverged as sister taxa after the sloth bear lineage and before the sun bear lineage.

Further investigations on the entire mitochondrial cytochrome b sequence indicate that the divergence of continental and Japanese black bear populations might have occurred when bears crossed the land bridge between the Korean peninsula and Japan 500,000 years ago, which is consistent with paleontological evidence.

Asian black bears are reproductively compatible with several other bear species, and have on occasion produced 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 an American black bear.

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