In Spiky Echidna, a baby echidna gets a piece of wire caught in between his spines. It takes a friendly possum to pull it out for him. The short-beaked echidna is a mammal called a monotreme. Its young hatches from leathery-shelled egg then stays in the small backward-facing pouch until its spines develop. If it is threatened, an echidna will roll up into a spiky ball on hard ground or dig quickly into soft ground.