THE SPINY ANT-EATERORECHIDNA
(Tachyglossus aculeatus)
NO one who looked at the portrait of the spiny ant-eater for the first time, and had no knowledge of its anatomy or history, would be likely to guess that it was a near relative of the duckbill. But in natural history, when we have to deal with members of different groups, externals count for very little, and all depends upon internal organisation. In the latter respect the echidnas, for there is more than one species, resemble in all essential features the duckbill, as they do in laying hard-shelled eggs, from which the young are eventually hatched. The single egg of the echidna, in place of being laid in a burrow, is, however, carried about by the female in a pouch developed for the purpose on the under side of her body shortly before the egg is laid; and in this same temporary pouch the young is likewise nurtured during the earlier stages of its existence.
The duckbill and the echidna afford an excellent example of the diversity of appearance produced in animals more or less nearly related to each other by specialisation and adaptation to totally distinct modes of life. In the duckbill the specialisation and adaptation are for an aquatic existence; in the echidna they are for a burrowing, terrestrial life and a diet of ants.
To an ant-eater teeth of any kind would be not only useless, but an actual hindrance, and they have accordingly been discarded, while the muzzle has been prolonged into a decidedly bird-like beak. In this respect the echidna much resembles the great South American ant-eater, which belongs to a totally different group of mammals.
To enable it to dig out the nests of the ants which form its chief food, and likewise to excavate the burrows in which it passes the day, the echidna is armed with powerful claws, those on the hind-feet being, however, much larger and more curved than those in front. It is with these strong hind-claws that the earth loosened by the fore-feet is thrown out from ants’ nests and the burrow. Like the porcupine, which is also a nocturnal and a burrowing creature, the echidna has its back protected with an array of parti-coloured horny spines mingled with hairs. The degree of development of the spines is, however, subject to great variation; and there is one race in which the hair predominates, and the spines appear only in the midst of the dense brown fur. Like the platypus, the echidna has no external ears.
echidna
The ordinary, or five-toed, echidna has a much more extensive range thanthe platypus, occurring, in suitable localities, not only all over Australia and Tasmania, but likewise in New Guinea. The last-named island is likewise the home of the much larger three-toed echidna (Proechidna bruijnii), in which the beak is longer, more slender, and distinctly curved, while the number of the toes on each foot is reduced to three.
With the commencement of evening the echidna issues forth from the lair or burrow, in which it has passed the day, in search of food—this comprising not only ants, both ordinary and white, but likewise such other insects and their grubs as may be encountered or dug up during the nocturnal wanderings. Soon after daybreak the creature returns to its burrow. During the hottest and driest part of the Australian summer spiny ant-eaters fall into a torpid condition, when they exist for weeks at a time on no other nourishment but their own fat. In cases of extreme hunger they are stated to fill their stomachs with sand. At the end of the dry season, when rain falls and the country resumes its verdure, the echidnas wake up, and the males relinquish their normally solitary life and take to themselves partners.
On occasions of danger the echidna has two means of defence—it can either roll itself up into a ball and present a sphere of spikes to its enemy, or it can burrow with such rapidity that it actually seems to sink into the earth as if swimming.
The single egg appears to be conveyed to the pouch by the female in her mouth, and the parent assists the young echidna, whose muzzle is armed with a special knob for that purpose, in breaking the shell. Naked and blind when first hatched, the young one remains in the pouch till its spines make their appearance, drawing its nutriment from two pores through which the milk flows. When the young echidna has been turned adrift in the world to shift for itself, the maternal breeding-pouch shrivels up, to be re-developed the following year.
As in the case of the platypus, no remains of extinct echidnas are found anywhere except in the superficial deposits of Australia itself. Certain teeth from rocks older than the Chalk, both in Europe and America, may, however, indicate the ancestral stock of the egg-laying group.