Polar bears (Ursus maritimus) give birth to their cubs in a den, where they will reside until the cubs are about 12 weeks old. Then, they will all emerge from their den, and the cubs will continue to live with their mother over the next 2-3 years, learning how to hunt, socialize, and generally, how to be a polar bear.
Art by @thandaart
[Edited by Isabelle McDonald]
Reference:
Owen, M. A. (2021). Polar bear maternal care, neonatal development, and social behavior. In Ethology and behavioral ecology of marine mammals (pp. 293–310). https://doi.org/10.1007/978-3-030-66796-2_15