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.