THE GIANT TORTOISE OF ALDABRA.
MR. WALTER ROTHSCHILD has procured for this country, and installed in the Zoological Society's collection, the oldest living creature in the world. It is one of the giant tortoises of Aldabra, sufficiently remarkable for its size, for it weighs a quarter of a ton, but even more interesting from the record of its age. This gives it a known life of one hundred and fifty years, with the unknown incre- ment of its age previous to its transportation to the island of Mauritius. It is, we believe, the same tortoise which was mentioned in the treaty between Great Britain and France when the island was ceded by the former country in 1810, and has therefore changed its status four times in a century and a half as a national heirloom.
When the length of the life of other animals is contrasted with that of the giant tortoise, it is clear that the latter must enjoy some special advantage, either of structure or of habit, conducing to longevity. One hundred years is a good old age for an elephant, and no other animals, except certain birds and reptiles, reach half this span of years. With this we may contrast the following instances of the length of years attained both by the smaller tortoises and the gigantic
species. In the Bishop's garden at Peterborough one died in 1821 which was said to have exceeded two hundred and twenty years. The Lambeth tortoise, which was introduced into the garden by Archbishop Land about the year 1625, and died in 1753, owing to some neglect of the gardener, lived in its "last situation" one hundred and twenty-eight years. In 1833, Sir Charles Colville, Governor of the Mauritius, sent to the Zoological Gardens a tortoise weighing 285 lb. It was 4 ft. 4 in. long, and had been in the Mauritius for sixty-seven years. The exact period was known, for this tortoise was brought to that island from the Seychelles in 1766 by the Chevalier Marion du Fresne. At that time it was full-grown, so that its real age was probably much greater. In the Museum of Natural History at South Kensington are the remains of an Aldabra tortoise, of the species now presented to the Zoological Society by Mr. Walter Rothschild, which, though only known to be eighty years old, weighed 870 lb., and was still growing at the time of its death.
The structure of the tortoises contributes a large share to their pre-eminence in length of life. Their bodies are spared the whole of that exhausting process of collapse and expansion which we call "breathing." The cruel wear and tear of this incessant motion, involving work of lungs, muscles, ribs, and air-passages, unnoticed in health, but one of the most dis- tressing facts revealed by illness, does not fall on the happy tortoise. His "shell," back-piece and breastplate alike, is as rigid as a piece of concrete. The "armour" of an armadillo rises and falls on his back at each respiration. That of the tortoise being an "outside skeleton" instead of a "process of the epidermis," he is kindly saved all this trouble. He sucks in air by making a vacuum with his tongue, and swallows it like water, the reservoir instead of a stomach being his capacious lungs. In addition to this enormous saving of energy, the tortoise enjoys two other structural advantages. He has no teeth to break, decay, get out of order, and ultimately starve him to death, like those of an old horse or a broken-toothed rabbit. Instead he has sharp horny edges to his mouth, which do not break or get out of order. And, lastly, there is his impenetrable shell. In reference to this, size is of a real advantage, for though small tortoises may live for centuries in Bishops' gardens, they have their enemies in the outer warld. Adjutant-storks swallow them whole and digest them, shell and all, and in California the golden eagle carries them up to a height and lets them fall on the rocks, thereby smashing their shells, as the Sicilian eagle was trying to do when he dropped the tortoise on the skull of JEschylus. Bat when a tortoise grows to a weight of 200 lb. there is no living animal which could injure it in any way. As it can swim it cannot drown ; its limbs are so constructed as to be little liable to fracture, and its interior is so arranged that it can fast for long periods, and has an internal reservoir of water, though it is naturally rather a thirsty animal. Charles Darwin, when among the giant tortoises of the Gala- pagos Islands, saw the newly-hatched young carried off by buzzards and carrion hawks, but the full-grown animals of 200 lb. weight seemed beyond the chance of any danger. He surmised that their deaths, when such took place, were only due to accident, such as falling over precipices, and inhabi- tants of the islands corroborated this conclusion.
Being "built to last," the tortoise's habits and character have to conform in some sort to the limitations set by its form. It is not tempted to waste energy in useless motion. On the other hand, the disposition of the land tortoises is eminently placid. This is by no means an inseparable accompaniment of slow and solidly-built reptiles. Toads, for example, have dreadful tempers, which induce them to fight battles on dusty roads, and lose their lives untimely. Then there is a hugh fat frog in Argentina which can only hop an inch at a time, but which is so irritable that he positively barks with fury, and almost bursts in his endeavours to come to close quarters and bite. But the tortoise "leads the life of tranquillity on the carpet of prudence," and neither "wears out" nor "rusts out." Yet they are less apathetic than might be supposed from the habits of the small species kept in English gardens. On the Galapagos Islands Darwin found that the giant tortoises were really not only the "oldest inhabitants," but the representa- tive creatures of the archipelago. They were living their own life very much at their ease ; but this was not quite
as devoid of incident as one might imagine. Both food and water are more common on the higher parts of the islands —which are extinct volcanoes—than near the coast. Fresh water, indeed, is only found up in the hills, and, as the tor- toises are very fond of water, they have to make long and uphill journeys to reach it. They make "broad and well- beaten paths" from the coast to the springs, and it was by following the tortoises' roads that the Spaniards first found the springs they needed to water the ships. "When I landed at Chatham Island," writes Mr. Darwin, "I could not imagine what animal travelled so methodically along the well-chosen tracks. Near the springs it was a curious spectacle to behold many of these great monsters,—one set eagerly travelling onwards with outstretched necks, and another set returning after having drunk their fill. When the tortoise arrives at a spring, quite regardless of any spectator, it buries its head in the water above its eyes, and greedily swallows great mouthfuls at the rate of ten a minute." On the dry lower ground the explorer found the giant tortoises munching up a succulent cactus. On the higher ground they ate leaves, fallen berries, and lichen.
A very curious fact in relation to the giant tortoises is their isolation on small, remote, ocean-surrounded islands at vast distances from land and from each other. Aldabra, for example, is a small uninhabited island in the Indian Ocean, north-west of Madagascar. Others are found in ocean archipelagoes, like the Seychelles, or recent volcanic islets, like the Galapagos off the Pacific coast of South America. One rather attractive theory for this isolation of the big tortoises traces their "plantation" on these desolate islands to the old buccaneers. It has been contended that the Galapagos Islands were the original home of the giant tortoises, and that the rovers, who stocked them on board ship and kept them alive for long periods, may have left them at places of call, even in remote oceans, during the long periods in which bucca- neering flourished. The Galapagos tortoise is now known to naturalists as the Testudo Indicus. But in the days of the Elizabethan discoverers, before the establishment of the "buccaneers," it was stated that the Spaniards held that "there were no other such tortoises in those seas except on the Galapagos."
This view, that in island groups the "creative force" may be traced in its origin, gains much colour from Mr. Darwin's discovery of an astonishing number of new species of birds and flowers on these islands, lying remote under the Equator at a distance of eight hundred miles from the mainland of South America. But it is also an argument in favour of the view that the giant tortoises of the Seychelles and Aldabra are also instances of separate and peculiar forms generated on specific and limited areas of earth, and developed and surviving under conditions of food and climate not precisely like those in any other place. But even so they are a curious anomaly. In most islands the tendency of animal life is to fall below rather than to rise above the normal size. But there are instances to the contrary even in the Mauritius, Bourbon, and Rodriquez, near the home of the Aldabra giant tortoises. Not to mention the roc of Madagascar, the dodo was the largest of all pigeons, and survived in considerable numbers after Mascarenhas discovered the islands, and the largest living representative of the family, the crowned pigeon of Nicobar, is also an island species.
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