Nile Crocodile Facts (Crocodylus niloticus)

The Nile crocodile (Crocodylus niloticus) is a large freshwater African reptile. It is responsible for the most deaths from any animal as a predator preying on humans, yet crocodiles serve an important ecological function. The Nile crocodile eats carcasses that pollute water and controls predatory fish that could overeat smaller fish used as food by many other species. Fast Facts: Nile Crocodile Scientific Name: Crocodylus niloticusCommon Names: Nile crocodile, African crocodile, common crocodile, black crocodileBasic Animal Group: ReptileSize: 10-20 feetWeight: 300-1650 poundsLifespan: 50-60 yearsDiet: CarnivoreHabitat: Freshwater wetlands of sub-Saharan AfricaPopulation: 250,000Conservation Status: Least Concern Description The Nile crocodile is the second-largest reptile in the world after the saltwater crocodile (Crocodylus porosus). Nile crocodiles have thick, armored skin that is dark bronze with black stripes and spots on the back, greenish-yellow side stripes, and yellow scales on the belly. Crocodiles have four short legs, long tails, and elongated jaws with conical teeth. Their eyes, ears, and nostrils are on top of the head. Males are about 30% larger than females. Average size ranges between 10 and 20 feet in length and anywhere from 300 to 1,650 pounds in weight. A Nile crocodile may carry her young in her mouth or on her back. Gallo Images-Roger De La Harpe / Getty Images Habitat and Distribution The Nile crocodile is native to Africa. It lives in freshwater marshes, swamps, lakes, streams, and rivers of sub-Saharan Africa, the Nile basin, and Madagascar. It is an invasive species in Florida, but it is unknown whether the population is reproducing. Although it is a freshwater species, the Nile crocodile has salt glands and sometimes enters brackish and marine waters. Diet and Behavior Crocodiles are apex predators that hunt animals up to twice their size. Young crocodiles eat invertebrates and fish, while larger ones may take any animal. They also feed on carcasses, other crocodiles (including members of their own species), and sometimes fruit. Like other crocodilians, they ingest stones as gastroliths, which may help digest food or act as ballast. Crocodiles are ambush predators that wait for prey to come within range, lunge at the target, and sink their teeth into it to drag it into water to drown, die from sudden thrashing movements, or be torn apart with help from other crocodiles. At night, crocodiles may leave the water and ambush prey on land. The Nile crocodile spends most of the day partially exposed in shallow water or basking on land. Crocodiles may bask with open mouths to prevent overheating or as a threat display for other crocodiles. Reproduction and Offspring Nile crocodiles reach sexual maturity between 12 and 16 years of age, when males are about 10 feet 10 inches long and females are between 7 and 10 feet long. Mature males breed every year, while females only breed once every two to three years. Males attract females by making noises, slapping their snouts in water, and blowing water out through their noses. Males may battle other males for breeding rights. Females lay eggs a month or two after breeding. Nesting can occur at any time of year, but tends to coincide with the dry season. The female digs a nest in the sand or soil several feet from the water and deposits between 25 and 80 eggs. The heat of the soil incubates the eggs and determines the sex of the offspring, with males only resulting from temperatures between 89 Â °F and 94 Â °F. The female guards the nest until the eggs hatch, which takes about 90 days. Near the end of the incubation period, the young make high-pitched chirps to alert the female to dig out the eggs. She may use her mouth to help her offspring hatch. After they have hatched, she may carry them in her mouth to water. While she guards her offspring for up to two years, they hunt their own food immediately after hatching. Despite her care, only about 10% of the eggs survive to hatching and 1% of hatchlings reach maturity. Mortality is high because the eggs and young are food for many other species. In captivity, Nile crocodiles live 50 to 60 years. They may have a potential lifespan of 70 to 100 years in the wild. A Nile crocodile has an egg tooth that it uses to help hatch from an egg. hphimagelibrary / Getty Images Conservation Status The Nile crocodile faced extinction in the 1960s. Today, the IUCN classifies the species conservation status as least concern. However, Nile crocodile numbers are decreasing. CITES lists the Nile crocodile under Appendix I (threatened with extinction) throughout most of its range. Researchers estimate 250,000 to 500,000 individuals live in the wild. Crocodiles are protected in part of their range and are raised in captivity. Threats The species faces multiple threats to its survival, including habitat loss and fragmentation, hunting for meat and leather, poaching, pollution, entanglement in fishing nets, and persecution. Invasive plant species also pose a threat, as they alter the temperature of crocodile nests and prevent eggs from hatching. Nile Crocodiles and Humans Crocodiles are farmed for their leather. In the wild, they have a reputation as man-eaters. The Nile crocodile together with the saltwater crocodile kills hundreds or sometimes thousands of people each year. Females with nests are aggressive, plus large adults hunt humans. Field biologists attribute the high number of attacks to a general lack of caution around crocodile-occupied areas. Studies indicate planned land management and public education could reduce human-crocodile conflict. Sources Crocodile Specialist Group 1996. Crocodylus niloticus. The IUCN Red List of Threatened Species 1996: e.T46590A11064465. doi:10.2305/IUCN.UK.1996.RLTS.T46590A11064465.enDunham, K. M.; Ghiurghi, A.; Cumbi, R. Urbano, F. Human–wildlife conflict in Mozambique: a national perspective, with emphasis on wildlife attacks on humans. Oryx. 44 (2): 185, 2010. doi:10.1017/S003060530999086XThorbjarnarson, J. Crocodile tears and skins: international trade, economic constraints, and limits to the sustainable use of crocodilians. Conservation Biology. 13 (3): 465–470, 1999. doi:10.1046/j.1523-1739.1999.00011.xWallace, K. M. A. J. Leslie. Diet of the Nile crocodile (Crocodylus niloticus) in the Okavango Delta, Botswana. Journal of Herpetology. 42 (2): 361, 2008. doi:10.1670/07-1071.1Wood, Gerald. The Guinness Book of Animal Facts and Feats. Sterling Publishing Co Inc., 1983. ISBN 978-0-85112-235-9.