Echidna s body is covered in spines that are modified hairs

Echidna.
Their spines are actually modified hairs. Echidnas' bodies (with the exception of their undersides, faces, and legs) are covered with 2-inch long spines. Fur between the spines provides insulation.
Echidnas live slow and long. Echidnas have the lowest body temperature of any mammal, 32°C (89°F). Their body temperatures are not controlled in the same way as that of other mammals, and can fluctuate by up 6–8°C over the course of the day. Their long life spans — up to 50 years in captivity, with anecdotal reports of wild animals reaching 45 years — are due to their low body temperature and slow metabolism.

National Geographic