Female kangaroos are born with a pouch called a marsupium, a specialized skin fold on the ventral side of the abdomen. Joeys are born in an underdeveloped state after a short gestation and crawl into the pouch, where they continue to develop and nurse.
The pouch is not a permanent feature in males. It develops in female joeys before birth and is fully formed by sexual maturity. It plays a vital role in nurturing and protecting the young during early development.