Echidnas, medium-sized animals that closely resemble porcupines or hedgehogs, are one of only two egg-laying mammals (the other being the duck-billed platypus) left in the world. Also called spiny anteaters, the timid creatures that are native to Australia are very elusive and hard to observe in the wild. Therefore, though they have been around for millions of years, very little is known about their lifestyle, making it almost impossible to breed the mammals in captivity.