CROCODILE, in a restricted sense, any reptile
of the genus Crocodilus, of which 12 living species occur in warm regions
of the world, or of two allied African genera, Osteolaemus and Osteoblepharon,
having a single species each; members of these 14 species are true crocodiles
as distinguished from the alligators. Broadly, however, the term crocodile
is used to denote any member of the order Crocodilia, or Loricata, which
includes, in addition to the 14 species of true crocodiles, two gavials,
one each in India and Malaysia; two alligators, one each in China and in
the United States; and seven caymans, all found in Central and South America.
The true crocodiles, having sharply tapering heads, expose the fourth tooth
on either side of the lower jaw in a notch on the outside of the upper
jaw. The broad-headed alligators and caymans have the fourth tooth concealed
in a matching socket in the overhanging upper jaw. The alligator is distinguished
from the gavial and crocodile by the teeth of the upper jaw, which overlap
those of the lower jaw markedly. The gavials are fish feeders exclusively
and are easily distinguished from others by their long narrow snouts, which
offer little resistance to the water when swung sidewise to catch fish.
The caymans of Central and South America are much like the alligators,
but they lack a bony septum in the nose. Crocodilians are survivors of
a group that flourished with the dinosaurs and once included specimens
over 50 feet (15 meters) long. Its earliest members date from the lower
Jurassic. They appear, from the fossil record, to have been most numerous
in Europe and North America until quite recent times. In the Pleistocene,
crocodilians have been found in India and Africa, as well as in Europe
and North America. Crocodilians are among the largest living reptiles,
but specimens are seldom as large as those described in print. The American
crocodile, C. acutus; the Orinoco crocodile, C. intermedius; and the marine
crocodile, C. porosus, found in the Australo-Malay Archipelago, all reach
about 23 feet (7 meters). The last named is reported to reach lengths of
more than 30 feet (9 meters), but such reports are probably exaggerations
or miscalculations. The Cuban crocodile, C. rhombifer, a rare species found
only in Cuba, reaches a length of 12 feet (3.6 meters). The smallest crocodilians
are the Chinese alligator, Alligator sinensis, which attains a length of
about 5 feet (1.5 meters), and one of the South American caymans, Caiman
palpebrosus, which seldom reaches a length of 4 feet (120 cm). Most crocodilians
live most of the time in the water, where they frequently float lazily
with only the nostrils, eyes, and ears, which are raised above the general
level of the head, projecting above the surface. At such times a fleshy
valve in the rear of the mouth prevents water from entering the air passages,
and an internal passage in the skull conducts air from the projecting nostrils
to the throat. The powerful, vertically flattened tail and webbed feet
facilitate swimming, but only the marine crocodile ventures far from land.
Crocodilians come ashore to build their nests and to lay their eggs, and
sometimes to bask in the sun, lying agape to dry out the leeches that infest
their mouths; when disturbed they run into the water with a speed that
is surprising in view of the tremendous girth of large specimens. The eggs,
laid in a pile of decaying vegetation or in holes in the sand, are ellipsoidal
in shape, and their shells are leathery. The young, on hatching, grow rapidly.
In captivity the young of the American alligator are about 18 inches (45
cm) long at the end of the first year, and at about the third year they
are roughly 3 feet (90 cm) long. The age of crocodilians has always been
exaggerated; the animals look old at birth, and this fact has led to much
fanciful speculation. Large specimens of any species may be assumed to
be in their thirties; exceptionally large individuals, in their forties.
Zoo specimens have lived 25 years, and one American alligator survived
56 years. Any large crocodilian, either on shore or in the water, may prove
dangerous to man. This reptile does not attack indiscriminately, but it
is fast. Its tail is flexible and powerful, and on land it can run well
in a straight line. Its characteristic attack is a slow, careless approach
terminating in a sudden rush. When its jaws are set in a large animal it
rotates or spins on its long axis, thus tearing its mouthful of flesh out
of the larger body. It sinks large animals in the water, eating the flesh
when it begins to decompose. In nature, full grown specimens have no enemies
but man. The young, however, are preyed upon by many large birds, mammals,
and fishes. Economically, crocodilians are definitely valuable, particularly
for their hides, which have been widely used for shoes, bags, belts, and
other purposes. This value has led to their extermination in many areas,
with the result that most nations now protect their crocodiles. Furthermore,
in some states of the United States, notably New York the sale of crocodilian
products is forbidden. See also ALLIGATOR; CAIMAN, GAVIAL; REPTILES. ROBERT
STUART MATHEWS
Copyright ¿ 1996 P. F. Collier, L. P. All rights reserved.
Thanks to the owner of
www.crocodile.org
for the permission to use this image and text at my page.