Reptiles: Alligator & Crocodile

Alligator and Caiman Range: alligators are found in the southern United States and eastern China; caimans are found in Central America and South America Habitat: grassy swamps and slow-moving rivers Crocodile Range: North, Central, and South America, Africa, Southeast Asia, and Australia Habitat: grassy swamps and slow-moving rivers Gharial Range: India Habitat: rivers with deep pools and sand or mud banks

Is it an alligator or a crocodile?

All the species of alligators, caimans, crocodiles, and gharial together are known as “crocodilians.” That is sometimes shortened to “crocs” and still refers to all the species as a group.
But many people want to know what the difference is between an alligator and a crocodile. If you really want to know for sure, you need to know the particular characteristics of each species. But don't worry—there are a few general ways to tell the two apart:
Shape of the jaw— Alligators tend to have wide, U-shaped, rounded snouts, while crocodiles tend to have longer, more pointed, V-shaped snouts.
Teeth— The fourth tooth on the lower jaw sticks up over the upper lip on crocodiles, so you can see it when their mouths are closed. In alligators, this fourth tooth is covered up.
Habitat— Crocodiles also have special glands in their tongues that can get rid of excess salt, so they tend to live in saltwater habitats. Alligators have these glands, too, but they don't work as well as the crocodiles', so alligators prefer to live in freshwater habitats.
With 23 species of crocodilians, though, these general rules don't always apply—there are exceptions!

Coming to their senses

Crocodilians are efficient hunters, and their senses are more powerful than those of most other reptiles. You may not be able to see a croc's ears, but they have excellent hearing. They have slits on their heads that lead to a well-developed inner ear, and the slits close up when they dive to keep water out.
Crocs can even hear their young calling from inside their eggshells! They also have keen eyesight above water, similar to an owl's. Their eyes are placed on top of their heads so they can see well as they cruise the water looking for prey. They can probably see some color, and they have good vision at night because their vertical pupils can open wider than our round ones to let in more light. Crocs have taste buds to taste their food, and special organs in their snouts give them a great sense of smell.

Dinnertime

Crocs are carnivores and eat whatever they can catch in the water or along the banks. That includes fish, turtles, frogs, birds, pigs, deer, buffalo, and monkeys, depending on the size of the croc. Gharials and false gharials are specialists, though—with their slender snouts, all they can catch are fish. Crocs don't chew their food. They either tear off large pieces and swallow them or swallow the prey whole if it's small enough. That means that the croc has to juggle the food around until it's in the right position, then toss its head back so the food falls down its throat. Some croc species can eat up to half their body weight in one meal. At the San Diego Zoo, the gharials get trout and giant goldfish.

Mama crocs

For such ancient, ferocious-looking animals, crocodilian moms take really good care of their hatchlings! Crocs are one of the few reptiles that watch out for and protect their young until they are old enough to be on their own. The cow (female croc) looks for just the right place to build a nest to lay her eggs.
Some species make a mound nest out of soil and vegetable material; others dig a hole in the sandy beach for their nest. The mama croc then settles in nearby to guard the eggs from predators that might try to dig them up and eat them. When the babies are ready to hatch, they make grunting or barking noises from inside the egg, and use a short little tooth on the end of their snouts called an “egg tooth” to start breaking out of the leathery shell. Some croc moms even help by gently biting the egg to open it up more easily.
After the young have hatched, the mom carries them to the water in her mouth (except for gharials, which have mouths that are too narrow), then guards them for most of the first year of their lives. Sometimes the hatchlings get to ride on her back, too. She will threaten or attack any predator that lurks too close, and in some species she will call the hatchlings to swim into her mouth for protection—making it look like she's swallowed them!

Come on in, the water's great!

Crocodilians are most at home in or near the water. They even look like they belong there, appearing like logs floating in a swamp or washed up on shore. Crocs can hold their breath underwater for more than an hour. But don't be fooled by their seeming lack of activity—crocs can swim up to 20 miles per hour (32 kilometers per hour), and run on land as fast as 11 miles per hour (17.6 kilometers per hour) for short distances if they need to!

What's their status?

Of the 23 crocodilian species, 12 are in need of conservation help. Many croc species were hunted by people for their skins to make shoes and luggage, and some have suffered from a loss of habitat. But there are conservation success stories, too. The American alligator Alligator mississippiensis was once considered endangered, but through protection plans, management, and captive propagation it has made a remarkable comeback. Efforts by the Crocodile Specialist Group, affiliated with the International Union of Conservation of Nature, are now under way to help other crocs that are still in trouble.


http://www.sandiegozoo.org/animalbytes/t-crocodile.html