The platypus lays eggs in its nest. When the babies come out of the eggs after about ten days, they hold on to the mother. The mother makes milk for the new babies. The platypus does not have nipples, but milk comes through small openings in the skin. The young platypus drinks the milk from the mother's skin while she lies on her back. At six weeks the babies have fur and are able to leave the burrow for short trips. After four months they no longer need their mother's milk.