Sydney's Taronga Zoo is celebrating its first baby echidnas, or puggles as they are better known, in almost 30 years.

The three babies hatched from their eggs in August and have now opened their eyes and are developing the spines characteristic of their species.

Echidnas are one of only two Australian mammals that lay eggs - the other is the duck-billed platypus.

The baby echidnas hatch after 10 days and are carried around by their mothers in a pouch-like skin fold for up to two months.