This animal is called echidna or spiny ansteater, and has a characteristic that is shared only by another animal, the platypus. Like this, the echidna is the only mammal born from an egg ... I find it strange?
I explain briefly:
The earliest forms of childbearing occurred in prehistoric ocean water. The fish gave birth to many small fish of the sea and of those, many were devoured. To avoid this, the evolution devised some different formulations of childbearing: some fish were hidden in the mouth of the mother, others sought shelter in ... for example anemones ... and other small fish were kept in capsules viscous. The last way to protect the lineage separated was evolved over time in typical eggs of reptiles.
The capsules were no longer viscous but tough. Eggs that were getting the fetus evolve and grow into predators, hunters and adults, but with a smaller size. When mammals appeared, how to give birth to offspring changed. The egg was fertilized in the mother and, even without having the capabilities of an adult, was birthed. Of course had to be cared for and fed by the mother, trying to ensure that offspring born (usually) helpless.
Well, in this evolutionary path of procreation, which seems normal that any mammal born from the mother and then her nursing care and to become more, not an egg as birds or reptiles. That is because the echidna evolutionary peculiarity: the echidna is born from an egg, therefore, how they procreate is not like reptiles but not like that of mammals.
But the way to incubate the egg is not such as birds or reptiles. The echidna lays an egg and it's in a cavity of the body to the coat. This allows you to navigate and provide warmth and protection while ... a good idea talking about survival. Then yes, the small born and would do what any mammal: nursing.