Litters usually consist of two cubs, though litters of 6 have been recorded. At birth, cubs weigh 10–16 ounces (280–450 g), and measure 8 inches in length. They are born with fine, gray, downlike hair, and their hind quarters are underdeveloped. They typically open their eyes after 28–40 days, and begin walking after 5 weeks. Cubs are dependent on their mother's milk for 30 weeks, and will reach independence at 16–18 months. At the age of six weeks, they attain 2 lb, by 8 weeks they reach 5 lb and by the age of 6 months they weigh 40–60 lb. They reach mating maturity at the age of three years, and attain their full growth at 5 years.
The average lifespan in the wild is 18 years. The record age of a wild specimen was 31 years, while that in captivity was 44 years.