The spiny anteaters, or echidnas, make up five of the six species in the order Monotremata. These are primitive mammals that lay eggs like reptiles but have hair and suckle their young. One species of spiny anteater, Tachyglossus aculeatus, lives in Australia, Tasmania, and New Guinea. A second, T. setosus, is slightly larger and resides only in Tasmania. The other three species (in the genus Zaglossus spp.) live only in New Guinea (further study may actually find them to be one species). The sixth monotreme species is the platypus (Ornithorhynchus anatinus), which bears little resemblance to the spiny anteaters, apart from the egg-laying habit.
Monotremes lay eggs and have an internal bone structure for limbs that emerge from the sides of their body. These characteristics are similar to those of reptiles. Also, like reptiles (as well as birds), they have a cloaca, or a single chamber into which the intestine, bladder, and reproductive organs all empty. However, monotremes also have hair, produce milk, and are warm-blooded. Their ability to keep their body temperature constant is not always very successful, so these animals may hibernate during cool weather.
A small organ located on the hind legs of the male gave the spiny anteaters their name of echidna, which means "adder," because it is connected to a poison gland. However, the fluid is not really very poisonous, and the animals are more likely to try to escape by digging when in danger. Spiny anteaters have powerful claws that let them furiously dig dirt, sending it flying sideways. As they do this they appear to sink into the ground, their back protected by tough, sharp spines.
A spiny anteater looks very much like a porcupine, and is often given that common name because it has numerous yellow-colored spines covering its brown furred body. Unlike porcupine spines, however, those of the spiny anteater do not have barbs that catch in the skin. When in danger, the 30-in (76 cm) long spiny anteater will often curl up into an impenetrable ball. Its face leaves no doubt that it is not a porcupine, being stretched forward into a slender, hairless snout with nostrils on the end. The tiny mouth, located on the bottom of the snout, opens only wide enough for a long, sticky tongue to emerge and haul in its food of termites and ants. A spiny anteater has no teeth. Instead, it chops up the tough bodies of its insect prey by smashing them against the roof of its mouth with its spiny tongue.
One New Guinea species (Zaglossus bruijni) has an especially long and slightly curved snout, and is called the long-nosed echidna. It has so much hair that its whitish spines are not readily visible. The tongue of this endangered species may be 12 in (30.5 cm) long.
Unlike marsupials, spiny anteaters have a pouch only during the breeding season, when an extra fold of skin develops. The female lays one leathery-shelled egg, which she places into the pouch. It soon hatches into a partially developed baby, only about half an inch long. The tiny offspring laps milk directly off the mother's fur, because monotremes have no nipples. The infant resides in the pouch only until its spines begin to grow and annoy the mother. It is then left in a hidden spot, where it continues to suckle and grow, and may hibernate. Spiny anteaters have been known to live in captivity as long as 50 years.
Kerrod, Robin. Mammals: Primates, Insect-Eaters and Baleen Whales. New York: Facts on File, 1988.
Jean F. Blashfield