1911 Encyclopædia Britannica/Galapagos Islands
GALAPAGOS ISLANDS, an archipelago of five larger and ten smaller islands in the Pacific Ocean, exactly under the equator. The nearest island to the South American coast lies 580 m. W. of Ecuador, to which country they belong. The name is derived from galápago, a tortoise, on account of the giant species, the characteristic feature of the fauna. The islands were discovered early in the 16th century by Spaniards, who gave them their present name. They were then uninhabited. The English names of the individual islands were probably given by buccaneers, for whom the group formed a convenient retreat.
The larger members of the group, several of which attain an elevation of 2000 to 2500 ft., are Albemarle or Isabela (100 m. long, 28 m. in extreme breadth, with an area of 1650 sq. m. and an extreme elevation of 5000 ft.), Narborough or Fernandina, Indefatigable or Santa Cruz, Chatham or San Cristobal, James or San Salvador, and Charles or Santa Maria. The total land area is estimated at about 2870 sq. m. (about that of West Riding of Yorkshire). The extraordinary number of craters, a few of which are reported still to be active, gives evidence that the archipelago is the result of volcanic action. The number of main craters may be about twenty-five, but there are very many small eruptive cones on the flanks of the old volcanoes. There is a convict settlement on Chatham with some 300 inhabitants living in low thatched or iron-roofed huts, under the supervision of a police commissioner and other officials of Ecuador, by which country the group was annexed in 1832, when General Villamil founded Floreana on Charles Island, naming it in honour of Juan José Flores, president of Ecuador. A governor has been appointed since 1885, some importance being foreseen for the islands in connexion with the cutting of the Panama canal, as the group lies on the route to Australia opened up by that scheme. Charles Island, the most valuable of the group is cultivated by a small colony. On many of the islets numerous tropical fruits are found growing wild, but they are no doubt escapes from cultivation, just as the large herds of wild cattle, horses, donkeys, pigs, goats and dogs—the last large and fierce—which occur abundantly on most of the islands have escaped from domestication.
The shores of the larger islands are fringed in some parts with a dense barrier of mangroves, backed by an often impenetrable thicket of tropical undergrowth, which, as the ridges are ascended, give place to taller trees and deep green bushes which are covered with orchids and trailing moss (orchilla), and from which creepers hang down interlacing the vegetation. But generally the low grounds are parched and rocky, presented only a few thickets of Peruvian cactus and stunted shrubs, and a most uninviting shore. The contrast between this low zone and the upper zone of rich vegetation (above about 800 ft.) is curiously marked. From July to November the clouds hang low on the mountains, and give moisture to the upper zone, while the climate of the lower is dry. Rain in the lower zone is scanty, and from May to January does not occur. The porous soil absorbs the moisture, and fresh water is scarce. Though the islands are under the equator, the climate is not intensely hot, as it is tempered by cold currents from the Antarctic sea, which, having followed the coast of Peru as far as Cape Blanco, bear off to the N.W. towards and through the Galapagos. The mean temperature of the lower zone is about 71º F., that of the upper from 66º to 62º.
The Galapagos Islands are of some commercial importance to Ecuador, on account of the guano and the orchilla moss found on them and exported to Europe. Except on Charles Island, where settlement has existed longest, little or no influence of the presence of man is evident in the group; still the running wild of dogs and cats, and, as regards the vegetation, especially goats, must in a comparatively short period greatly modify the biological conditions of the islands.
The origin and development of these conditions, in islands so distinctly oceanic as the Galapagos, have given its chief importance to this archipelago since it was visited by Darwin in the “ Beagle.” The Galapagos archipelago possesses a rare advantage from its isolated situation, and from the fact that its history has never been interfered with by any aborigines of the human race. Of the seven species of giant tortoises known to science (although at the discovery of the islands there were probably fifteen) all are indigenous, and each is confined to its own islet. There also occurs a peculiar genus of lizards with two species, the one marine, the other terrestrial. The majority of the birds are of endemic species peculiar to different islets, while more than half belong to peculiar genera. More than half of the flora is unknown elsewhere.
Since 1860 several visits have been paid to the group by scientific investigators—by Dr Habel in 1868; Messrs Baur and Adams, and the naturalists of the “ Albatross,” between 1888 and 1891; and in 1897–1898 by Mr Charles Harris, whose journey was specially undertaken at the instance of the Hon. Walter Rothschild. Very complete collections have therefore, as a result of these expeditions, been brought together; but their examination does not materially change the facts upon which the conclusions arrived at by Darwin, from the evidence of the birds and plants, were based; though he ” no doubt would have paid more attention to [the evidence afforded by Land-tortoises], if he had been in possession of facts with which we are acquainted now ” (Günther). His conclusions were that the group “ has never been nearer the mainland than it is now, nor have its members been at any time closer together ”; and that the character of the flora and fauna is the result of species straggling over from America, at long intervals of time, to the different islets, where in their isolation they have gradually varied in different degrees and ways from their ancestors. Equally indecisive is the further exploration as to evidence for the opinion held by other naturalists that the endemic species of the different islands have resulted from subsidences, through volcanic action, which have reduced one large island mass into a number of islets, wherein the separated species became differentiated during their isolation. The presence of these giant reptiles on the group is the chief fact on which a former land connexion with the continent of America may be sustained. “Nearly all authorities agree that it is not probable that they have crossed the wide sea between the Galapagos Islands and the American continent, although, while they are helpless, and quite unable to swim, they can float on the water. If their ancestors had been carried out to sea once or twice by a flood and safely drifted as far as the Galapagos Islands” (Wallace), “they must have been numerous on the continent” (Rothschild and Hartert). No remains, and of course no living species, of these tortoises are known to exist or have existed on the mainland. Rothschild and Hartert think “it is more natural to assume the disappearance of a great stock of animals, the remains of which have survived, ... than to assume the disappearance in comparatively recent times (i.e. in the Eocene period or later) of enormous land masses.” Past elevations of land, however (and doubtless equally great subsidences) have taken place in South America since the Eocene, and the conclusion that extensive areas of land have subsided in the Indian Ocean has long been based on a somewhat similar distribution of giant tortoises in the Mascarene region.
Authorities.—Darwin, Voyage of the “Beagle”; O. Salvin, “On the Avifauna of the Galapagos Archipelago,” Trans. Zool. Soc. part ix. (1876); Sclater and Salvin, “Characters of New Species collected by Dr Habel in the Galapagos Islands,” Proc. Zool. Soc. London, 1870, pp. 322–327; A. R. Wallace, Geographical Distribution of Animals (New York, 1876); Theodor Wolf, Ein Besuch der Galapagos Inseln (Heidelberg, 1879); and paper in Geographical Journal, vi. 560 (1895); W. L. and P. L. Sclater, The Geography of Mammals (London, 1899); Ridgway, “Birds of the Galapagos Archipelago,” Proc. U.S. Nat. Mus. vol. xix. pp. 459–670 (1897); Baur, “New Observations on the Origin of the Galapagos Islands,” Amer. Nat. (1897), pp. 661–680, 864–896; A. Agassiz, “The Galapagos Islands,” Bull. Mus. Comp. Zool. vol. xxiii. pp. 56-75; A. Günther, Proc. Linn. Soc. (London (President’s Address), October 1898), pp. 14-29 (with bibliography from 1875 to 1898 on gigantic land-tortoises); Rothschild and Hartert, “Review of the Ornithology of the Galapagos Islands,” Novitates zoologicae, vi. pp. 85-205; B. L. Robinson, “Flora of the Galapagos Islands,” Proc. Amer. Acad. of Arts and Sciences, xxxviii. (1902).