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Alligators and Crocodiles
Nature Bulletin No. 519-A March 2, 1974
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
ALLIGATORS AND CROCODILES
The crocodilians, which include alligators, caimans, crocodiles and the
gavial, are living fossils -- swamp dwelling survivors from the Age of
Reptiles when dinosaurs ruled the earth. Almost every tropical country
has one or more kinds of them and in Columbia, South America, there
are seven or eight. Only the two species of alligators live in more
temperate regions: one in the United States and the other, almost
extinct, in the Yangtze valley of China.
The American Alligator is now common only in the watery interior of
Florida, the great Okefenokee Swamp and the Louisiana bayous. The
American Crocodile, of which a few remain in Everglades National
Park and the Florida Keys, ranges through the West Indies and from
southern Mexico to Ecuador. The most obvious difference between
them is that an alligator's snout is much broader. The crocodile is far
more vicious.
The body of a crocodilian merges imperceptibly into its massive tail
which serves to propel the animal in water and also as a weapon. With
a swift sideswipe of that tail, a big "croc" can knock a man down and
break his leg. On land, except when sliding into water, the body is
carried considerably above the ground by its four thick legs --
sometimes at amazing speed. The back is protected by a tough armor
of horny scales reinforced by plates of bone.
A crocodilian gets most of its food in water and takes to water for
protection, but loves to bask on sunny banks and the females must
have land on which to lay their eggs. Its nostrils are on top of the tip of
the snout and its eyes are on top of the head, so that when completely
submerged except for those four inconspicuous bumps, the sly creature
can breathe comfortably while watching all around it. The air passage
from the nostrils to the throat and lungs can be closed by a flap,
enabling it to seize an animal under water or remain there several
hours without drowning.
Alligators dig deep caves, sometimes 40 feet long, with an entrance
below the surface of a favorite pool or stream, where they retreat from
danger and spend the winters. During the spring mating period both
sexes, especially the males, wander from place to place. Then, at
night, the bulls are very noisy. Their bellow is a deep booming roar
that can be heard a mile away.
The female builds her nest on a spot of high ground, gathering fresh
vegetation, trash and mud which, with her snout and belly, she
fashions into a mound which may be three feet high. In this she lays
several dozen long leathery eggs and, for two months, jealously guards
them while they are incubated by the heat of the sun and decaying
debris. when they are ready to hatch, and the young make grunting
noises inside their shells, she tears off the top of the nest so that they
may escape and forage for themselves. Few survive the first year, most
of them being eaten by other creatures of the swamp.
An alligator grows rapidly. By the end of the first year, it is about 18
inches in length. In five years it may become six feet long. Until then,
in many Florida counties, an alligator may not legally be captured nor
hunted for its valuable hide. In the 1700's the naturalist, William
Bartram, reported alligators so thick in the St. Johns River, Florida,
that he could have crossed that broad stream by walking on their backs
and some measured 20 feet in length. Nowadays their numbers have
been greatly reduced and few get to be more than 10 feet long. Unless
it is teased, or guarding its nest, an alligator will rarely attack a
person.
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