Best Jungle Life: 07/25/12

Crocodiles & Crocodile Pics

Description Of Crocodiles

Crocodiles are similar to alligators and caimans; for their common biology and differences between them, see Crocodilia.

Crocodiles are among the more biologically complex reptiles despite their prehistoric look. Unlike other reptiles, a crocodile has a cerebral cortex, a four-chambered heart,and the functional equivalent of a diaphragm, by incorporating muscles used for aquatic locomotion into respiration (e.g. m. diaphragmaticus);^[6] Its external morphology, on the other hand, is a sign of its aquatic and predatory lifestyle.

A crocodile’s physical traits allow it to be a successful predator. Its streamlined body enables it to swim swiftly. It also tucks its feet to the side while swimming, which makes it faster by decreasing water resistance. Its webbed feet, though not used to propel the animal through the water, allow it to make fast turns and sudden moves in the water or initiate swimming. Webbed feet are an advantage in shallower water where the animal sometimes moves around by walking.

Crocodiles have a palatal flap, a rigid tissue at the back of the mouth that blocks the entry of water. The palate has a special path from the nostril to the glottis that bypasses the mouth. The nostrils are closed during submergence. Like other archosaurs, crocodilians are diapsid, although their post-temporal fenestrae are reduced. The walls of the braincase are bony, but lack supratemporal and postfrontal bones.^[7] Their tongues are not free, but held in place by a membrane which limits movement; as a result, crocodiles are unable to stick out their tongues.^[8]

Crocodilian scales have pores believed to be sensory in function, analogous to the lateral line in fishes. They are particularly seen on their upper and lower jaws. Another possibility is they are secretory, as they produce an oily substance that appears to flush mud off.^[7]

Crocodiles are very fast over short distances, even out of water. Since they feed by grabbing and holding onto their prey, they have evolved sharp teeth for tearing and holding onto flesh, and powerful muscles to close the jaws and hold them shut. These jaws can bite down with immense force, by far the strongest bite of any animal. The pressure of the crocodile's bite is more than 5,000 pounds per square inch (30,000 kPa),^[9] compared to just 335 pounds per square inch (2,300 kPa) for a Rottweiler, 400 pounds per square inch (2,800 kPa) for a large great white shark, 800 pounds per square inch (6,000 kPa) to 1,000 pounds per square inch (7,000 kPa) for a hyena, or 2,000 pounds per square inch (10,000 kPa) for a large alligator^{[citation needed]}. The jaws are opened, however, by a very weak set of muscles. Crocodiles can thus be subdued for study or transport by taping their jaws or holding their jaws shut with large rubber bands cut from automobile inner tubes. They have limited lateral (side-to-side) neck movement

Crocodiles & Crocodile Pics

Biology and behavior

Crocodiles are ambush hunters, waiting for fish or land animals to come close, then rushing out to attack. As cold-blooded predators, they have a very slow metabolism, so they can survive long periods without food. Despite their appearance of being slow, crocodiles are top predators in their environment, and various species have been observed attacking and killing sharks.^[10]
Herodotus claimed Nile crocodiles had a symbiotic relationship with certain birds, such as the Egyptian plover, which enter the crocodile's mouth and pick leeches feeding on the crocodile's blood; with no evidence of this interaction actually occurring in any crocodile species, it is most likely mythical or allegorical fiction.^[11]
Many large crocodilians swallow stones (called gastroliths or stomach stones) which may act as ballast to balance their bodies or assist in crushing food,^[7] similar to grit in birds.
Salt glands are present in the tongues of most crocodylids and they have a pore opening on the surface of the tongue. They appear to be similar to those in marine turtles; they seem to be absent in Alligatoridae.^[7]
Crocodilians can produce sounds during distress and in aggressive displays. They can also hear well, but their tympanic membranes are concealed by flat flaps that may be raised or lowered by muscles.^[7]are concealed by flat flaps that may be raised or lowered by muscles
Crocodiles eat fish, birds, mammals and occasionally smaller crocodiles.
Crocodiles are protected in many parts of the world, but they also are farmed commercially. Their hides are tanned and used to make leather goods such as shoes and handbags; crocodile meat is also considered a delicacy. The most commonly farmed species are the saltwater and Nile crocodiles, while a hybrid of the saltwater and the rare Siamese crocodile is also bred in Asian farms. Farming has resulted in an increase in the saltwater crocodile population in Australia, as eggs are usually harvested from the wild, so landowners have an incentive to conserve their habitat.Crocodiles are more closely related to birds and dinosaurs than to most animals classified as reptiles, the three being included in the group Archosauria ('ruling reptiles'). See Crocodilia for more information.
Crocodile embryos do not have sex chromosomes, and unlike humans, sex is not determined genetically. Sex is determined by temperature, with males produced at around 31.6 °C (89 °F), and females produced at slightly lower and higher temperatures. The average incubation period is around 80 days, and also is dependent on temperature.^[12]
Crocodiles may possess a form of homing instinct. Three rogue saltwater crocodiles were relocated 400 kilometres by helicopter in northern Australia, but had returned to their original locations within three weeks, based on data obtained from tracking devices attached to the reptiles.^[13]
The land speed record for a crocodile is 17 km/h (11 mph) measured in a galloping Australian freshwater crocodile.^[14] Maximum speed varies from species to species. Certain species can indeed gallop, including Cuban crocodiles, New Guinea crocodiles, African dwarf crocodiles, and even small Nile crocodiles. The fastest means by which most species can move is a kind of "belly run", where the body moves in a snake-like fashion, limbs splayed out to either side paddling away frantically while the tail whips to and fro. Crocodiles can reach speeds of 10 or 11 km/h (around 7 mph) when they "belly run", and often faster if slipping down muddy riverbanks. Another form of locomotion is the "high walk", where the body is raised clear of the ground.
Crocodiles do not have sweat glands and release heat through their mouths. They often sleep with their mouths open and may even pant like a dog.^[15]
The BBC TV^[16] reported thee Nile crocodile which has lurked a long time underwater to catch prey, has built up a large oxygen debt. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone.