The American Black Bear (Ursus americanus) is the most widespread and smallest bear species native to North America. While commonly called “black bears,” their coat color varies widely, ranging from black to cinnamon, brown, or even bluish-gray depending on the region. The adult physical dimensions, weight, and growth trajectory of this species are highly variable. This variability depends on several biological and environmental factors, which this article explores alongside the typical measurements of a fully grown bear.
Standard Dimensions of the American Black Bear
Adult black bears exhibit a wide range of measurements. A typical adult male, often called a boar, has an overall body length from snout to tail ranging between 1.5 to 2.1 meters (5 to 7 feet). When standing on all four paws, the shoulder height averages between 0.75 and 1.05 meters (2.5 to 3.5 feet). Males generally weigh between 170 and 270 kilograms (375 to 600 pounds) in the autumn before hibernation.
Females, or sows, are noticeably smaller than males in nearly all dimensions. Their body length typically ranges from 1.2 to 1.7 meters (4 to 5.5 feet), and their shoulder height is slightly lower. An adult female’s weight usually ranges from 90 to 200 kilograms (200 to 450 pounds) during the peak feeding season. When standing upright on its hind legs, a black bear can reach a height of approximately 1.6 to 1.75 meters (5.3 to 5.8 feet).
Sexual and Geographic Size Variation
Size variation in black bears is primarily explained by two factors: sexual dimorphism and the productivity of the local environment. Sexual dimorphism is pronounced, with males consistently outweighing females by a significant margin. Adult male black bears are generally 10 to 70% heavier and 15 to 25% longer than their female counterparts.
Geographic location and the abundance of food resources also cause substantial differences in overall size. Bears in resource-rich areas, such as the northern and eastern parts of North America, often grow larger than those in drier, resource-scarce environments. For example, average adult male weight in the Great Smoky Mountains National Park was around 112 kilograms, while males in New York averaged closer to 135 kilograms. The most massive individuals are typically found in the coastal regions of the Pacific Northwest, where easily accessible, high-calorie foods allow for greater accumulation of fat and muscle.
Growth Rate and Maturation
Black bear growth begins with an extremely small cub, born in the winter den weighing only 200 to 450 grams (less than one pound). This tiny size relative to the adult is among the smallest observed in placental mammals. Cubs grow rapidly while nursing in the den, weighing between two and five kilograms by the time they emerge in the spring.
Cubs remain dependent on their mother for approximately 16 to 18 months. They gain weight quickly during their first year, reaching 18 to 27 kilograms by six months of age. Although females may reach sexual maturity around three to five years old, their full physical growth typically plateaus between six and eight years of age. Males continue to gain size for a longer period, often growing until they are 10 to 12 years old, which helps them attain the size necessary to establish dominance for breeding.