Classification: Introduced Species Nile crocodiles have been recently captured in South Florida, though no signs that the population is reproducing in the wild have been found. 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. The animals likely were either brought there to be released or are escapees.

Description: Adult Nile crocodiles have a dark bronze colouration above, with faded blackish spots and stripes variably appearing across the back and a dingy off yellow on the belly, although mud can often obscure the crocodile's actual colour. The flanks, which are yellowish-green in colour, have dark patches arranged in oblique stripes in highly variable patterns. Some variation occurs relative to environment; specimens from swift flowing waters tend to be lighter in colour than those dwelling in murkier lakes or swamps, which provides camouflage that suits their environment, an example of clinal variation. Nile crocodiles have green eyes. The colouration also helps to camouflage them; juveniles are grey, multicoloured, or brown, with dark cross-bands on the tail and body. The underbelly of young crocodiles is yellowish green. As they mature, Nile crocodiles become darker and the cross-bands fade, especially those on the upper body. A similar tendency in coloration change during maturation has been noted in most crocodile species.

Size: Adult male Nile crocodiles usually range in length from 10 feet 10 inches to 16 feet 5 inches long; at these lengths, an average sized male may weigh from 330 to 1,650 lbs. Very old, mature ones can grow to 18 feet 1 inch or more in length. Large mature males can reach 2,200 lbs., or more in weight. Mature female Nile crocodiles typically measure 7 feet 3 inches to 12 feet 6 inches, at which lengths the average female specimen would weigh 88 to 551 lbs.

Habitat: Nile crocodiles may be able to tolerate an extremely broad range of habitat types, including small brackish streams, fast flowing rivers, swamps, dams, and tidal lakes and estuaries. They are found mostly in rivers, lakes, marshes, and dams, favoring open, broad bodies of water over smaller ones. They are often found in waters adjacent to various open habitats such as savanna or even semi-desert but can also acclimate to well wooded swamps, extensively wooded riparian zones, waterways of other woodlands and the perimeter of forests.

Range: The Nile crocodile is presently the most common crocodilian in Africa, and is distributed throughout much of the continent. Introduced into extreme southern florida.

Found in these States: FL

Diet: The Nile crocodile mostly hunts within the confines of waterways, attacking aquatic prey or terrestrial animals when they come to the water to drink or to cross. The Nile crocodile possesses unique predation behavior characterized by the ability of preying both within water, where it is best adapted, and out of it, which often results in unpredictable attacks on almost any other animal up to twice its size. Most hunting on land is done at night by lying in ambush near forest trails or roadsides, up to 170 feet from the water's edge.

Reproduction: On average, sexual maturity is obtained from 12 to 16 years of age. For males, the onset of sexual maturity occurs when they are about 10 feet 10 inches long and mass of 342 lbs., being fairly consistent. On the other hand, that for females is rather more variable, and may be indicative of the health of a regional population based on size at sexual maturity. On average female sexual maturity occurs when they reach 7 feet 3 inches to 9 feet 10 inches in length. Similarly, a wide range of studies from southern Africa found that the average length for females at the onset of sexual maturity was 7 feet 8 inches. However, stunted sexual maturity appears to occur in populations at opposite extremes, both where crocodiles are thought to be overpopulated and where they are overly reduced to heavy hunting, sometimes with females laying eggs when they measure as small as 4 feet 11 inch although it is questionable whether such clutches would bear healthy hatchlings.

During the mating season, males attract females by bellowing, slapping their snouts in the water, blowing water out of their noses, and making a variety of other noises. Among the larger males of a population, territorial clashes can lead to physical fighting between males especially if they are near the same size. Such clashes can be brutal affairs and can end in mortality but typically end with victor and loser still alive, the latter withdrawing into deep waters. Once a female has been attracted, the pair warble and rub the undersides of their jaws together. Compared to the tender behaviour of the female accepting the male, copulation is rather rough, in which the male often roars and pins the female underwater. In some regions, males have reportedly mated with several females, perhaps any female that enters his claimed territory, though in most regions annual monogamy appears to be most common in this species.

Females lay their eggs about one to two months after mating. The nesting season can fall in nearly every month of the year. In the northern extremes of the distribution (i.e. Somalia or Egypt), the nesting season is December through February while in the southern limits (i.e. South Africa or Tanzania) is in August through December. In crocodiles between these distributions egg-laying is in intermediate months, often focused between April and July. The dates correspond to about a month or two into the dry season within that given region. The benefits of this are presumably that nest flooding risk is considerably reduced at this time and the stage at which hatchlings begin their lives out of the egg falls roughly at the beginning of the rainy season, when water levels are still relatively low but insect prey is in recovery. Preferred nesting locations are sandy shores, dry stream beds, or riverbanks. The female digs a hole a few metres from the bank and up to 20 inches deep, and lays on average between 25 and 80 eggs. The number of eggs varies and depends partially on the size of the female. The most significant prerequisites to a nesting site are soil with the depth to permit the female to dig out the nest mound, shading to which mother can retire during the heat of the day and access to water. She finds a spot soft enough to allow her to dig a sideways slanted burrow. The mother Nile crocodile deposits the eggs in the terminal chamber and packs the sand or earth back over the nest pit. While, like all crocodilians, the Nile crocodile digs out a hole for a nest site, unlike most other modern crocodilians, female Nile crocodiles bury their eggs in sand or soil rather than incubate them in rotting vegetation. The female may urinate sporadically on the soil to keep it moist, which prevents soil from hardening excessively. After burying the eggs, the female then guards them for the three-month incubation period. Nests have been recorded seldom in concealed positions such as under a bush or in grasses, but normally in open spots on the bank. It is thought the Nile crocodile cannot nest under heavy forest cover as can two of the three other African crocodiles because they do not use rotting leaves (a very effective method of producing heat for the eggs) and thus require sunlight on sand or soil the surface of the egg chamber to provide the appropriate warmth for embryo development. In South Africa, the invasive plant Chromolaena odorata has recently exploded along banks traditionally used by crocodiles as nesting sites and caused nest failures by blocking sunlight over the nest chamber.

At a reported incubation period of about 90 days, the stage is notably shorter than that of the American alligator (110 to 120 days) but slightly longer than that of the mugger crocodile. Nile crocodiles have temperature-dependent sex determination (TSD), which means the sex of their hatchlings is determined not by genetics as is the case in mammals and birds, but by the average temperature during the middle third of their incubation period. If the temperature inside the nest is below 89.1 ℉ ℉, or above 94.1 ℉ ℉, the offspring will be female. Males can only be born if the temperature is within that narrow range. The hatchlings start to make a high-pitched chirping noise before hatching, which is the signal for the mother to rip open the nest. It is thought to be either difficult or impossible for hatchlings to escape the nest burrow without assistance, as the surface may become very heavy and packed above them. The mother crocodile may pick up the eggs in her mouth, and roll them between their tongue and the upper palate to help crack the shell and release her offspring. Once the eggs hatch, the female may lead the hatchlings to water, or even carry them there in her mouth, as female American alligators have been observed doing.

Hatchling Nile crocodiles are between 11 and 12 inches long at first and weigh around 2.5 oz. The hatchlings grow approximately that length each year for the first several years. The new mother will protect her offspring for up to two years, and if there are multiple nests in the same area, the mothers may form a creche. During this time, the mothers may pick up their offspring either in their mouths or gular fold (throat pouch) to keep the babies safe. The mother will sometimes carry her young on her back to avoid natural predators of the small crocodiles, which can be surprisingly bold even with the mother around. Nile crocodiles of under two years are much more rarely observed than larger specimens, and more seldom seen than the same age young in several other types of crocodilian. Young crocodiles are shy and evasive due to the formidable array of predators that they must face in sub-Saharan Africa, spending little time sunning and moving about nocturnally whenever possible. Crocodiles two years old and younger may spend a surprising amount of time on land, as evidenced by the range of terrestrial insects found in their stomachs, and their lifestyle may resemble that of a semiaquatic midsized lizard more so than the very aquatic lives of older crocodiles. At the end of the two years, the hatchlings will be about 3 feet 11 inches long, and will naturally depart the nest area, avoiding the territories of older and larger crocodiles. After this stage, crocodiles may loosely associate with similarly sized crocodiles and many enter feeding congregations of crocodiles once they attain 6 feet 7 inches, at which size predators and cannibal crocodiles become much less of a concern. Crocodile longevity is not well established, but larger species like the Nile crocodile live longer, and may have a potential average life span of 70 to 100 years, though no crocodilian species commonly exceeds a lifespan of 50 to 60 years in captivity.

Status: Since the last Crocodilus niloticus assessment in 1996, genetic analysis confirmed two lineages of African Crocodylus, namely C. niloticus and C. suchus. This assessment takes account of this recent information and only considers the range of C. niloticus. This range represents the majority of habitat and populations on which previous continent-wide assessments of the Nile Crocodile were based. Despite some evidence of localised population declines, C. niloticus (sensu novo) generally remains widespread and as the population has not significantly changed, the assessment LC remains the same. West African populations constituting C. suchus are likely depleted and less numerous and will be assessed separately.

Taxonomy: