Their milk oozes out of mammary gland ducts and collects in grooves on their skin-where the nursing babies lap it up or suck it from tufts of fur.
![platypus lay eggs platypus lay eggs](https://www.gtgoodtimes.com/wp-content/uploads/2018/04/2.png)
But unlike all other mammals, monotremes like the platypus have no nipples. Like all mammals, monotreme mothers produce milk for their young. The platypus is one of just a handful of mammals that lay eggs. When she does leave, she plugs the den opening with dirt.
![platypus lay eggs platypus lay eggs](https://cdn.iflscience.com/images/72235111-d810-5749-b62a-9a5056fbb5c9/default-1610033307-an-egg-laying-semi-aquatic-mammal-that-sweats-milk-and-glows-in-the-dark-why-not-lukas-vejrik-shutterstock-com.jpg)
Giving birth this way is extremely unusual among living mammals-but normal for most other animals. The platypus is a monotreme-a group where the females produce offspring by laying eggs.
![platypus lay eggs platypus lay eggs](https://i.ytimg.com/vi/z0-qFKpktkA/maxresdefault.jpg)
The unique nature of the curiously constructed platypus starts even before birth and marches on from there. The eggs are laid directly into this pouch. Along stretches of its native rivers in eastern Australia, the female platypus digs a burrow near a stream and fills it with soft leaves as a place to lay eggs. Echidnas have backward-facing pouches (somewhat like the pouch of a marsupial).