Asian black bear
Biologically and morphologically, Asiatic black bears represent the beginning of the arboreal specializations attained by sloth bears and sun bears. Asiatic black bears have karyotypes 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, Asiatic 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. Scientists have proposed that Asiatic black bears are either a surviving, albeit modified, form of "Ursus etruscus", specifically the early, small variety of the Middle Villafranchian (Upper Pliocene to Lower Pleistocene) or a larger form of "Ursus minimus", an extinct species that arose 4,000,000 years ago. With the exception of the age of the bones, it is often difficult to distinguish the remains of "Ursus minimus" with those of modern Asiatic black bears.
Formosan black bear
The Formosan bear lives in the mountainous forests in the eastern two-thirds of Taiwan at elevations of . In the winter, rather than hibernating like Asiatic black bears in temperate areas, they move to lower elevations to find food. They are active for 54–57% of daylight hours, and more active during summer (60%) and fall/winter (60%) than spring (47%). They are primarily active during the day in the spring and summer; and increasingly active at night in the fall/winter when acorns are abundant. They are solitary and usually move around extensively except during the mating season or when caring for cubs. Formosan bears are also the only bears on the planet that make temporary nests.