Which animal has a gestation period of only 13 days?

The opossum has an exceptionally short gestation period of about 13 days.

The figure usually refers to the Virginia opossum, North America’s only marsupial. Its gestation typically lasts roughly 11 to 13 days, after which the extremely undeveloped young are born and crawl into the mother’s pouch. They are tiny at birth, around the size of a honeybee.

This rapid birth is possible because marsupials complete much of their development after birth rather than inside the uterus. Newborn opossums attach to teats inside the pouch, where they continue growing for weeks before becoming more mobile. A Virginia opossum generally has 13 teats, though a litter can contain more young than can successfully nurse.

The answer is sometimes misunderstood as applying identically to every opossum species. Gestation varies among species; the gray short-tailed opossum, for example, is commonly reported at around 14 to 15 days. In standard trivia, “opossum” means the Virginia opossum associated with the approximately 13-day figure.