The American black bear, Ursus americanus, is the most widespread but smallest of North America’s three bear species. An individual black bear’s weight is highly variable and constantly changes based on biological and environmental factors. Understanding its weight requires looking beyond a single average figure and acknowledging the dynamic nature of its body mass throughout the year.
Typical Adult Weight: Male vs. Female
American black bears exhibit significant sexual dimorphism, meaning there is a noticeable difference in size between the sexes. Adult males, or boars, are substantially larger than adult females, or sows. Males generally weigh 30% to 50% more than females.
A typical adult male black bear weighs between 130 and 550 pounds (60–250 kg). Females usually fall within a narrower range of 90 to 300 pounds (40–136 kg). These figures represent a general average and can vary widely depending on the bear’s age and the time of year.
The Impact of Season and Habitat
The most dramatic fluctuations in a black bear’s weight are dictated by the annual cycle of seasons. In late summer and fall, bears enter hyperphagia, a state of excessive eating necessary to prepare for winter hibernation. During this time, an adult bear may consume over 20,000 calories a day and gain multiple pounds daily.
This intense foraging allows a bear to gain 20% to 50% of its body weight in fat reserves before denning. For example, a bear weighing 300 pounds in the summer might weigh over 400 pounds before entering its den. They emerge in the spring at their lowest body mass, having metabolized fat stores to survive the months of inactivity.
Habitat Differences
Weight is strongly correlated with food availability, which varies greatly by habitat. Bears in resource-rich coastal areas, such as those with access to annual salmon runs, tend to be heavier than those in food-scarce inland regions.
Bears near human development or agricultural areas, which offer high-calorie, accessible food sources, also maintain a consistently higher weight. These regional differences can result in a 100-pound bear and a 500-pound bear being the same age.
Maximum Recorded Weight and Cub Size
While most adult male black bears rarely exceed 500 pounds in the wild, maximum recorded weights highlight the potential for growth in nutrient-rich environments. The heaviest American black bear on record was a male from New Brunswick, Canada, estimated to weigh 1,000 pounds (453 kg). Other verified records include bears exceeding 800 pounds, though individuals of this size are rare outliers.
The massive size of an adult bear contrasts sharply with the size of a newborn cub. Cubs are born in the den during the winter months, typically in January or February. At birth, a black bear cub is remarkably small, weighing only about 8 to 16 ounces (0.5 to 1 pound). This tiny size relative to the mother underscores the incredible growth rate achieved in the first year of life.