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Saturday, June 25, 2011

The Beauty Nile Crocodile


Beauty Of Animal | The Beauty Nile Crocodile | In antiquity, Nile crocodiles occurred in the Nile delta and the Zarqa River (Jordan), and they are recorded by Herodotus to have inhabited Lake Moeris. They are thought to have become extinct in the Seychelles in the early 19th century. It is known from fossil remains that they once inhabited Lake Edward. The Nile crocodile's current range of distribution extends from the Senegal River, Lake Chad, Wadai and the Sudan to the Cunene and the Okavango Delta. In Madagascar, crocodiles occur in the western and southern parts from Sembirano to Port Dauphin. They have occasionally been spotted in Zanzibar and the Comoros. Until recently, many permanent waters in the Sahara still housed relict populations.

In West Africa, Nile crocodiles are found most frequently in coastal lagoons, estuaries, and in the rivers bordering the equatorial forest belt. In East Africa, they are found mostly in rivers, lakes, marshes, and dams. They have been known to enter the sea in some areas, with one specimen having been seen 11 km off St Lucia Bay in 1917. In Madagascar, they have adapted to living in caves. Nile crocodiles have a dark bronze colouration above, with black spots on the back and a dirty purple on the belly. The flanks, which are yellowish green in colour, have dark patches arranged in oblique stripes. There is some variation relative to environment; specimens from swift flowing waters tend to be lighter in colour than those dwelling in lakes or swamps. They have green eyes.

Like all crocodiles, they are quadrupeds with four short, splayed legs; long, powerful tails; a scaly hide with rows of ossified scutes running down their back and tail; and powerful jaws. They have nictitating membranes to protect their eyes and have lachrymal glands, and can cleanse their eyes with tears. Nostrils, eyes, and ears are situated on the tops of their head, so the rest of the body can remain concealed underwater. Their coloration also helps them hide: Juveniles are grey, multicoloured, or brown; with darker cross-bands on their tail and body. As they mature they become darker and the cross-bands fade, especially those on the body. The underbelly is yellowish, and makes high-quality leather.

They normally crawl along on their bellies, but they can also "high walk" with their trunks raised above the ground. Smaller specimens can gallop, and even larger crocodiles are capable of surprising bursts of speeds, briefly reaching up to 12 to 14 km/h (7.5 to 8.5 mi/h). They can swim much faster by moving their body and tail in a sinuous fashion, and they can sustain this form of movement much longer at about 30 to 35 km/h (18 to 22 mi/h).

They have a three-chambered heart which is often mistaken as four-chambered due to an elongated cardiac septum, which is physiologically similar to the four chambered heart of a bird, which is especially efficient at oxygenating their blood. They normally dive for only a couple of minutes, but will stay underwater for up to 30 minutes if threatened, and if they remain inactive they can hold their breath for up to 2 hours. They have an ectothermic metabolism, so they can survive a long time between meals  though when they do eat, they can eat up to half their body weight at a time. They have a rich vocal range, and good hearing. Their skin has a number of poorly understood integumentary sense organs (ISOs), that may react to changes in water pressure.

The bite force exerted by an adult Nile crocodile has been shown by Dr. Brady Barr to measure 5,000 lbf (22 kN). However, the muscles responsible for opening the mouth are exceptionally weak, allowing a man to easily hold them shut with a small amount of force. Their mouths are filled with a total of 64 to 68 cone-shaped teeth. On each side of the mouth, there are 5 teeth in the front of the upper jaw (the premaxilla), 13 or 14 in the rest of the upper jaw (the maxilla), and 14 or 15 on either side of the lower jaw (the mandible). Hatchlings quickly lose a hardened piece of skin on the top of their mouth called the egg tooth, which they use to break through their egg's shell at birth.

Outside water crocodiles can meet concurrence with other dominant Savanna predators, notably felines such as lions and leopards. Occasionally, both will hunt and prey on each other, depending on size, if regular food becomes scarce.The Nile crocodile is the largest crocodilian in Africa and is sometimes regarded as the second largest crocodilian after the saltwater crocodile. The male crocodile usually measure from 11.5 to 16 feet long (3.5 to 5 meters), but very old, mature ones can grow to 18 ft (5.5 m) or more. Like all crocodiles they are sexually dimorphic, with the males up to 30% larger than the females, though the difference is even more in some species, like the saltwater crocodile. Mature female Nile crocodiles measure 8 to 13 ft (2.4 to 4.0 m) Typical Nile crocodile weight is 225 kg (500 lb), though 730 kg (1,600 lb) is possible. The largest accurately measured male was shot near Mwanza, Tanzania and measured 6.45 m (21.2 ft) and weighed approximately 1,090 kg (2,400 lb)
 
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