"Canst thou draw out Leviathan* with a fishhook?
Or press down his tongue with a cord?
Dare to lay thy hand upon him:
ye shall not do so again."
Job 40: 25, 32
* Sumero-Acadian name for a mythical monster, applied in the Book of Job to the Nile crocodile
American crocodile, Crocodylus acutus, female. Enriquillo National Park, south-western Dominican Republic, Hispaniola.
Their very appearance spells "ancient" and, indeed, that is what they are.
ORDER CROCODYLIA: CROCODILES, ALLIGATORS, AND GAVIALS
The group contains crocodiles, caimans, alligators, and gavials. Like turtles, this is a very ancient lineage that saw the dinosaurs come and go. The largest living reptiles are the Nile crocodile (Crocodylus niloticus) of Africa, and the saltwater or marine crocodile (C. porosus) of south-east Asia and Australia. Both may reach more than seven meters in length and over 500 kilograms in weight. The gavial (Gavialis gangeticus) can be almost as large. The smallest living representative of the group is the West African dwarf crocodile, Osteolemus tetraspis, with an average of one meter in length.
Although, as with turtles, their ancestors date as far back as the
early Triassic period, in certain respects crocodilians are the
most advanced of the non-avian reptiles. Their hearts are
four-chambered, and with such arrangement they achieve at least a
partial separation of arterial and venous blood in their
circulatory systems, thus allowing them to make better use of the
available oxygen. They also have a sort of diaphragm and their
brains possess a cortex.
All modern crocodilians are aquatic. However, the group was much more diverse in a distant geological past, when terrestrial species were common. Some extinct semi-aquatic species (Deinosuchus and others) were 15-meter monsters that weighted thousands of kilograms and preyed even upon dinosaurs. Others were even more adapted to water, their legs transformed into fins like a seal's, and with a vertical lobe on the tail, which thus looked like that of a fish.
Most at home in water, all crocodilians however lay their eggs on land. Females prepare nests in the form of mounds of mud and rotting vegetation in which they lay their clutches. The heat created by the mass of soil and decomposing leaf litter incubates the eggs. Uncharacteristically among reptiles, female crocodiles fiercely defend their eggs and neonates, keeping guard over them and driving off or killing any potential nest robber that gets too close. They may even help their neonates reach the safety of water by carefully picking them up with their jaws festooned with sharp teeth and tenderly carrying them in such fashion to a safe part of their lake or river.
When in land, crocodilians may look slow and ponderous as they slowly gait bodies to bask on sand bars or mud banks. However, appearances can be highly deceitful. Many a crocodile and caiman can easily outrun a man when in a hurry.
Modern crocodilians are sarcophages that prey on any hapless animal that they can capture and subdue. While neonates and juveniles feed on insects, fish, and frogs, adults will prey on waterfowl, rats, dogs, deer, antelope, and even humans. The largest species in Africa are perfectly capable of capturing and tearing apart buffaloes and zebras.
Another universal trait among crocodiles and their relatives is their nocturnal habits. Although it is common to see them very visibly basking out of water and even hunting during the day, it is at night when they truly come into their own. All have elliptical pupils that close down to a slit under bright daylight. At night, the pupils will open completely, allowing them to make good use of whatever little light there is. Indeed, one of the easiest ways to find them at night is by the eerie reflection of the light of a torch or flashlight on their retinas. Most species are actually shy creatures that will generally avoid contact with humans at all cost. However, their staring cat's eyes and their apparent grins bristling with fangs contribute to give them an aura of malevolent intelligence which cause many people to consider them more dangerous than they really are.
While all crocodilians have the same bodily frame, crocodiles (properly speaking, family Crocodylidae) can be told apart from their relatives - caimans and alligators (family Alligatoridae), and gavials (family Gavialidae) - by looking carefully at their snouts. In all crocodiles the largest tooth near the front of the mandible can be seen when the animal has its mouth closed. The tooth will fit into a lateral socket in the maxilla. In other members of the order, this tooth will be hidden inside the mouth when it is closed.
The toothy "grins" of American crocodiles, Crocodylus acutus, two males and a female.
In the third photograph, the largest tooth near the tip of the mandible can be seen against
the upper jaw even when the animal closes its mouth, distinguishing it as a "true" crocodile.
Enriquillo National Park, south-western Dominican Republic, Hispaniola.
Finally, and as far as a general description goes, some crocodilians are the most vocal of reptiles after birds and some geckoes. Especially during mating seasons, males may emit rumbling roars and bellows that may carry for long distances. Having a true voice is a trait that perhaps makes them resemble their distant relatives: dinosaurs, including birds.
Few representatives of this order inhabit the West Indies. The spectacled caiman, Caiman crocodilus, has been introduced into Puerto Rico and Cuba, and is a vagrant to some of the Lesser Antilles from South America.
Among native Antillean species, the American crocodile, Crocodylus acutus, naturally extends its range into the Greater Antillean islands of Cuba, Jamaica, and Hispaniola. It is reasonably common in places like the hypersaline Lake Enriquillo and Etang Saumatre, in Hispaniola. Elsewhere in the Caribbean islands, its numbers have declined dramatically, or it has disappeared altogether.
Crocodylus acutus. Enriquillo National Park, south-western Dominican Republic, Hispaniola.
Crocodiles can be surprisingly powerful and fast when startled or attacking prey.
They can go from total immobility to explosive speed in
the blink of an eye.
The Cuban crocodile, Crocodylus rhombifer, is endemic to that island, and today is one of the most endangered of crocodilians. Nowadays it is common only in the Zapata swamp and its surroundings. The species feeds mainly on Cuban hutias, a native rodent resembling a giant rat, as well as on waterfowl and the occasional stray dog or cat. The Cuban crocodile is peculiar in being perhaps the most terrestrial member of its order. Also, although it is by no means the largest living crocodile, it has the reputation of being one of the most aggressive toward any intruders.
Cuban crocodiles, Crocodylus rhombifer.
National Zoo, Washington, D.C., United States.