Bears (Ursidae) are fascinating mammals whose young begin life in an extremely vulnerable state within a winter den. Understanding the biology and terminology reveals much about the species’ survival strategies. A young bear’s journey involves total reliance on its mother for an extended period, which shapes its ability to thrive in the wild.
The Definitive Name
The definitive name for a baby bear is a cub. This term is used across all eight bear species, including the American black bear, brown bear, polar bear, and giant panda. The word “cub” also describes the young of other large carnivores, such as lions and wolves. It is thought to originate from the Old English word “cub,” historically applied to the young of various small animals. Terms like “kit” or “whelp” are incorrect nomenclature for bear offspring.
The First Year of Life
Bear cubs are born during the mother’s winter dormancy, typically in a den between January and February. They are born in a remarkably underdeveloped, altricial state due to delayed implantation, which times the birth to a period of safety and fasting. Newborn cubs are completely dependent, being blind, toothless, and nearly hairless. A newborn usually weighs only about one pound (0.45 kilograms) and measures around 9.4 inches long.
The first few weeks are spent in the den, where the cub feeds on its mother’s rich milk and grows quickly. A cub’s eyes typically open around four to six weeks of age, and its fur grows dense by the end of March. When the family emerges from the den in the spring, usually around April, the cub has gained enough mobility to walk and follow the sow. This denning period results in intense growth, with cubs weighing between three and nine pounds upon emergence.
Names Across All Bear Species
The term “cub” is the consistent name for all offspring in the Ursidae family. Specific terms are used for age classification, such as “cubs of the year” (COY) for those born in the current year, or “yearlings” for those in their second year. Cubs remain with their mother, or sow, for an extended period to learn necessary survival skills, including foraging, hunting, and identifying threats. This dependency period varies by species, lasting approximately 1.5 years for American black bears and up to 2.5 to 3 years for grizzly and polar bears. After this time, the young bear leaves the sow to begin life as a subadult.