1. American Black Bear (Ursus americanus):
- Cubs are born weighing around 10-12 ounces (283-340 grams) and measure about 8 inches (20 centimeters) in length.
- Adults typically weigh between 100 and 600 pounds (45-272 kilograms) and stand 2-3 feet (61-91 centimeters) tall at the shoulder.
2. Grizzly Bear (Ursus arctos horribilis):
- Grizzly bear cubs weigh approximately 1-2 pounds (0.45-0.9 kilograms) at birth and are around 8 inches (20 centimeters) long.
- Adult grizzlies can reach weights of 500 to 1,000 pounds (227-454 kilograms) and stand 3-4 feet (91-122 centimeters) tall at the shoulder.
3. Polar Bear (Ursus maritimus):
- Polar bear cubs weigh around 1-2 pounds (0.45-0.9 kilograms) at birth and measure approximately 18 inches (46 centimeters) in length.
- Adult polar bears are much larger, with males typically weighing between 770 and 1,500 pounds (350-680 kilograms) and standing 9-10 feet (274-305 centimeters) tall at the shoulder. Females are smaller, usually weighing between 330 and 550 pounds (150-250 kilograms) and standing 7-8 feet (213-244 centimeters) tall.
4. Brown Bear (Ursus arctos):
- Brown bear cubs are born weighing about 1-2 pounds (0.45-0.9 kilograms) and measure around 10 inches (25 centimeters) in length.
- Adult brown bears exhibit significant size variations across subspecies. For example, the Kodiak bear (Ursus arctos middendorffi), a subspecies of brown bear found in Alaska, is known for its large size, with males weighing up to 1,500 pounds (680 kilograms) and females reaching up to 1,000 pounds (454 kilograms).
It's important to note that these are general ranges, and individual bears within the same species can exhibit varying sizes based on factors such as genetics, nutrition, and habitat conditions.