The Nile crocodile ( Crocodylus niloticus) is an African crocodile , the largest freshwater predator in Africa, and may be considered the second largest extant reptile in the world, after the saltwater crocodile ( Crocodylus porosus ).
One of the three species of crocodile found in Africa , the Nile crocodile inhabits larger rivers, lakes, estuaries and swamps in sub-Saharan Africa, the Nile basin and Madagascar.
The Nile crocodile is characterized by its four short, splayed legs, a flat, powerful tail, a scaly hide and a strong jaw. Adult males can reach up to 20 feet in length and weigh well over 1,000 pounds .
While it does come h to bask on hot days, the Nile crocodile is primarily designed to be hidden in the water. The placement of ears, eyes and nostrils on the top of the skull allow it to stay nearly submerged all day, and its olive coloring also aids in concealment.
The Nile crocodile feeds on fish, antelope, zebras and buffalos, leaping up to catch nesting birds or to pull large animals beneath the water. It also has a well-deserved reputation for killing humans, since its habitat is in close proximity to people.
Like other crocodilians , it can bite but cannot chew, which is awkward when hunting larger prey. As a solution, the Nile crocodile drags large prey underwater, using a twirling method, called a “death roll,” to tear off large chunks of flesh . The crocodile’s mouth is filled with 68 teeth and is capable of exerting impressive force while clamping onto prey.
Populations were bought nearly to extinction in the mid-20th century, as the Nile crocodile was hunted for leather and meat. National protections and international trade regulations have helped them rebound in many areas. The species is still threatened by illegal hunting, pollution and habitat loss. There are an estimated 250,000 to 500,000 species left in the wild.
Like other crocodilians, Nile crocodiles have temperature-dependent sex determination, which means the sex of their hatchlings is determined not by genetics, but by the average temperature during a portion of their incubation period . Offspring will be male only if the temperature inside the nest falls between the narrow range of 89.1 F and 94.1 F. Otherwise, offspring will be female.
Nile crocodiles are an invasive species in North America, and several specimens have been recently captured in southern Florida , though there are not yet signs that the population is reproducing in the wild. Genetic studies of Nile crocodiles captured in the wild in Florida have revealed that the specimens are all closely related to each other, suggesting a single source of the introduction. This source remains unclear, as their genetics do not match samples collected from captives at various zoos and theme parks in Florida. When compared to Nile crocodiles from their native Africa, the Florida wild specimens are most closely related to South African Nile crocodiles. It is unknown how many Nile crocodiles are currently at large in Florida. It is likely that the animals were either brought there to be released, or that they are escapees.
Nile crocodiles normally dive for only a few minutes at a time, but can swim underwater for up to 30 minutes if threatened, and if they remain fully inactive they can hold their breath for up to two hours (which, as aforementioned, is due to the high levels of lactic acid in their blood). They have a rich vocal range, and good hearing . Nile crocodiles 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 individuals are capable on occasion of surprising bursts of speed, briefly reaching up to 12 to 14 km/h (7.5 to 8.7 mph). They can swim much faster by moving their bodies and tails in a sinuous fashion, and they can sustain this form of movement much longer than on land, with a maximum known swimming speed 30 to 35 km/h (19 to 22 mph), more than three times faster than any human.