- Echidnas have mammary glands: All mammals have mammary glands, which are used to produce milk to feed their young. Echidnas have two mammary glands located on their underside, and they produce a milky secretion that their puggles (baby echidnas) lap up.
- Echidnas are warm-blooded: Mammals maintain a constant internal body temperature, regardless of the external environment. Echidnas are able to do this through a combination of their fur, which insulates them from the cold, and their ability to regulate their metabolism.
- Echidnas are covered in fur: Most mammals have fur, and echidnas are no exception. Their fur is made up of long, coarse hairs that help to keep them warm. Additionally, echidnas have a layer of spines underneath their fur that helps to protect them from predators.
- Echidnas give birth to live young: Most mammals give birth to live young, and echidnas are no exception. Echidnas give birth to a single puggle after a gestation period of about 21 days. The puggle is born blind and helpless, but it quickly grows and develops.
- Echidnas have specialized teeth: Echidnas have a unique set of teeth that are adapted for their diet of ants and termites. Their teeth are long and pointed, and they have a rough surface that helps to grind up the insects they eat.
Based on these characteristics, it is clear that echidnas are mammals, despite their distinctive appearance.