Animal portraiture

by Richard Lydekker

THE DUCKBILL OR PLATYPUS

(Ornithorhynchus anatinus)

FOR many years it was reported by the natives of Australia that the extraordinary warm-blooded quadruped known to naturalists as the duckbill, or platypus, produced its young from eggs laid in a burrow by the female. That a mammal—and a mammal, although of an altogether peculiar and out of the way type, the creature undoubtedly is—should lay eggs was, however, too much for the minds of stay-at-home naturalists, and the fiat accordingly went forth that the native story was to be discredited. And discredited it therefore was. In nature, as in other things, truth will, however, ultimately prevail; and we now know for certain that the female lays in a burrow in the bank of some river or pool a couple of hard-shelled, oval eggs, which in due course hatch out into naked, helpless young, furnished with soft sucking lips. Not that they suck in the ordinary mammalian fashion, for the female platypus has no nipples, but her milk oozes out in the breast from a number of sieve-like pores, from the surface of which it is sucked up by her offspring.

Such a difference from the ordinary mammalian way of doing business proclaims the wide distinction between the platypus, and, it may be added, its relatives the spiny ant-eaters or echidnas (one of which forms the subject of another illustration), and all other warm-blooded quadrupeds. Nor is this all, for in the structure of their skeleton and soft internal parts the platypus and the echidna display many marks of affinity with reptiles and birds, which are totally wanting in other mammals. These two creatures represent indeed a group by themselves, so that mammals may be divided into two great primary sections, the one embracing only the two egg-laying types, and the other all the rest.

And it is not a little significant that the egg-layers are confined to Australia and New Guinea, the home of many other primitive and ancient types which have disappeared from the rest of the world. In one sense indeed the platypus and the echidna are not exactly primitive creatures, as they have several specialised characters which were evidently wanting in their ancestors. They may rather be described as specialised branches of an ancient and primitive stock.

The duckbill is a heavily made aquatic mammal of about the size of a very short-legged rabbit, with blackish, mole-like fur above, passing gradually into whitish beneath, and a short, thick, tapering tail. The very short limbs terminate in thick toes, connected together by a web and armed with strong, pointed claws. In the fore-feet the margin of the web projects considerably beyond the claws, but on the rare occasions that the animal leaves the water the margin is folded downward beneath the claws, so as to leave the claws exposed. In museum-specimens, however, the web is almost invariably shown fully expanded, as in the accompanying illustration; a condition in which it would obviously be impossible for the animal to walk on land.

The most remarkable external feature of the duckbill is undoubtedly the duck-like, naked beak, pierced with two holes representing the nostrils. In stuffed specimens, at any rate, this beak is dark-coloured and horny in consistence, and looks as though it did not belong to the animal, but in life it is soft and tender. Medium-sized, dark eyes complete the physiognomy of this strange creature, in which external ears are wanting.

The internal arrangements of the mouth of the duckbill are scarcely less curious than the exterior. In early life the mouth is furnished, both above and below, with three pairs of somewhat quadrangular cheek-teeth, with raised and cusped margins. Beneath these grow up certain large horny plates, and about the time that full maturity is attained the teeth become worn out, and are finally shed, thus leaving the horny plates as the sole masticating organs.

This replacement of the teeth by horny plates appears to be connected with the nature of the food, for while in early life the duckbill appears to subsist mainly on water insects and other comparatively soft aquatic creatures, later on it takes to feeding almost entirely on bivalve shells of one particular species; and for crushing the stout shells of these molluscs it has been suggested that the tough horny plates are better suited than brittle teeth.

Duckbills, except when in their burrows, pass the greater portion of their time in the water, selecting quiet pools for their favourite haunts. In such situations they may be seen on a still evening floating and diving, and looking more like bottles in the water than anything else. They obtain their food chiefly by probing in the mud with their duck-like beaks. The dwelling-chamber of the burrow is situated in the bank above the water level, but its entrance is below the surface, although there is also an exit on the land. In the pairing-season the males, which are armed with a poison-bearing spine on the inside of each hind-leg, fight fiercely among themselves.

The duckbill, of which there is but a single species, is absolutely confined to southern and eastern Australia and Tasmania; and its nearest living relative is the echidna, of which a picture and notice follow.

THE SPINY ANT-EATER OR
ECHIDNA

(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.

The ordinary, or five-toed, echidna has a much more extensive range than the 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.