Crocodiles are oviparous, and their eggs are provided with resistant shells. These eggs are deposited by the female in some secluded place in the sand on the banks of the river, and are hatched simply by the ambient heat, without any assistance from the mother. The female Crocodiles of the Nile deposit their eggs where the solar heat soon brings them to maturity. In certain countries, such as the neighbourhood of Cayenne and Surinam, the eggs are buried under a kind of mound which the Alligators raise in damp places by gathering together leaves and herbaceous stems. This vegetable debris undergoes a kind of fermentation, the result of which is an increase of temperature, which, joined to that of the atmosphere, produces the desired result.
Lacépède describes an egg in the Museum of Natural History in Paris, which was laid by a Crocodile fourteen feet in length, which was killed in Upper Egypt. This egg is only two inches and five lines in its greatest diameter; in its least diameter it is one inch and eleven lines. It is oval and whitish. Its shell is cretaceous in substance, like the eggs of birds, but not so hard. At the time of their birth the little Crocodiles are only about six inches in length, but their growth is very rapid. They abound in large rivers in the tropics, and in marshy places near their banks. They often come on shore, for they are amphibious. In the night they watch for their prey. They feed exclusively on flesh—that is to say on fish, small Mammalians, aquatic birds, and reptiles. When they have seized a large object they drag it under the water, where it soon dies by asphyxia; there they leave it to macerate, when they eat it by instalments. In this manner men are sometimes carried away by Crocodiles, but it is contrary to the habits of the animal to suppose that they are devoured immediately. When a Crocodile has succeeded in seizing a negro, it does not devour him till the body becomes decomposed, when it can tear it to pieces with greater facility.
From the general structure of their bony framework it is difficult for Crocodiles to turn round or move otherwise than forward. This circumstance renders it easy to escape their pursuit. When chased by a Crocodile, it can be avoided by describing a circle, or running in a succession of curves. Upon the banks of the Lake of Nicaragua, in America, an Englishman was once pursued by an Alligator which had surprised him when on its margin. The animal was gaining upon him rapidly, when some Spaniards who witnessed the scene cried out to him to run round it. Thus fortunately warned the pursued dodged the Alligator, and escaped from his dangerous enemy ([Fig. 33]).
Fig. 33.—The Englishman and the Caiman, or the Circular Flight.
[No specimens of the Crocodilidæ have been found in Europe, and until very recently none had been found in Australia, but they are very common in the new colony of Queensland, an Alligator twenty feet long having been shot on the banks of the Mackenzie river, which was afterwards exhibited at Rockhampton. Crocodiles, properly so called, are found in Africa, Asia, and America. The Gavials seem to be limited to the Ganges and other large rivers in India. Besides the Gavial, Asia produces three other species, namely, C. vulgaris, C. galeatus, and C. bifurcatus. Of the first, Siam is the chief locality; the others are found in the rivers which debouch into the Indian Ocean and the Ganges.
The Alligatoridæ
Include the Jacares, Alligators, and Caimans.
The Jacares have the head oblong and depressed, with a ridge across the face in front of the eyes; teeth unequal, canines of the lower jaw fitting into a pit in the upper jaw; toes only partially webbed, eyelids fleshy, nostrils separated by a cartilage. Five species are described—namely, J. fissipes, from Tropical America, six feet in length; J. sclerops, from the Brazils; J. Nigra, also from the Brazils; J. punctulatus, with triangular oblong head, muzzle elongated, thin and flat, with a rounded point in front, and a slight enlargement behind the nostrils; J. vallefrons, differing slightly from the above—both natives of the Brazils.
Alligators have the jaws oblong, much depressed, broad and nearly parallel; forehead with a small longitudinal ridge between the orbits; feet fringed, toes half webbed, the outer toes free; nostrils separated by a bony septum rising from the upper edge, muzzle lengthening with age. One species only is known, which is a native of North America; it attains a length of six to seven feet, and is known also as Crocodilus Mississipensis.