Female platypuses secrete milk through mammary gland openings in the skin, as they have no nipples. Young lap milk directly from the skin folds. Milk is rich in nutrients and immune factors. This adaptation is ideal for a semi-aquatic environment where traditional nursing could be difficult. Mothers curl around the young in burrows to ensure access. Milk production supports rapid juvenile growth and survival. It is a primitive feature among monotremes, reflecting early mammalian evolution.
Nipple-free lactation suits semi-aquatic life.
It provides nourishment in burrowed nests without spillage.
Platypus young lap nutrient-rich milk from skin openings.
Smithsonian National Zoo (si.edu)