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Nile Crocodile @ Ndumo Game Reserve. Photo: Håvard Rosenlund

Nile Crocodile

Nile Crocodile - Crocodylus niloticus - Distribution MapThe Nile crocodile (Crocodylus niloticus) is the largest reptile in Africa, and the second largest reptile in the world after the saltwater crocodile (Crocodylus porosus). The average size of the Nile crocodile is a length of 4.1-5 meters (13-15 ft) and a weight of 410 kg (900 lb). Larger individuals do occur and some have been measured over 6 meters (20 ft) and with a weight up to 1000 kg (2,200 lb). Animals of that size is not very common anymore, after a surge of hunting in the 1940s and 50s, and the decrease in large wetland habitats.

Diet and habitat

Nile crocodiles are found in almost any suitable water habitat, such as rivers, dams, marshes, and lakes. They are at the top of the food chain as apex predators wherever they are found, both in and outside of the water. They will hunt what they can catch, and what they eat depends on the size of the crocodile. Small and young Nile crocodiles tend to eat small fish, invertebrates, small reptiles, and amphibians, while sub-adults can go for birds, fish, larger reptiles and small mammals up to the size of small antelopes. Adult crocodiles will try and catch almost any animal, and the very large specimens have even been known to go for black rhinoceros, hippopotamus and young elephants. In East Africa, for example, antelopes and other herbivores take up the bulk of the prey base, while in other areas, like in Lake St Lucia in South Africa, fish take up the largest portions of caught prey. Crocodiles that eat fish tend not to become as large as those who eat larger mammals. Because of their metabolism, crocodiles can go for long periods between meals, but when they eat they can ingest food up to half their body weight.

Here is a video of a Nile crocodile gliding through the water:

Hunting

The Nile crocodile is known for its hunting behaviour, where it lays in the water with only the eyes and nostrils showing. Upon spotting a potential prey, they slowly glide towards it, dives under the surface, and then, when close enough, attacks its prey with immense force and speed. It grabs a hold on to its prey with powerful jaws and will try to drag its victim into the water where it will try to drown it or kill it by tearing it apart, often with other crocodiles. Fish eating crocodiles often use their tails to hurl fish onto the banks, or they will lay in wait downstream and catch any fish that comes by. Sometimes they cooperate by blocking schools of fish. The Nile crocodile also hunts on land, but its short legs make it hard to chase prey. Instead of chasing, it will stay in cover along trails that lead down to the water at night and catch unsuspecting prey that walks past.

Reproduction

A female Nile crocodle will reach sexual maturity when reaching a length of 2-2.5 m (6 ft 7 in – 8 ft 2 in), and a male upon reaching a length of 3 m (9 ft 10 in). This will take approximately 10 years. During the mating season, males will try to lure females over by throwing their heads around, blowing water through their noses and creating various sounds and bellows. The largest males tend to be most successful. After two months, the female will lay 25-80 eggs in a nest she has dug out in the sand. After they are laid, she will bury them and guard them throughout an incubation period of three months. With the help of the father, she will try to fend off predators, but nests are often raided, as sometimes both parent need to leave the nest temporarily to cool down.

The hatchlings will give a high-pitched sound before hatching to alert the mother that it is time to open the nest. Parents may aid them in hatching by gently cracking the shells in their mouths. When hatched, young will be about 300 mm (12 in) long. The female will lead her offspring to the water, and will sometimes carry them in her mouth. What sex the offspring has depends on the temperature during the incubation period. Males are created at a temperature of 31.7°C (89.1°F) to 34.5°C (94.1°F) during the middle third of the incubation period. Females are created at temperatures both below and above this. The mother will care for her young for two years. After two years, the offspring will be 1.2 m (4 ft) long and ready for a life as independent crocodiles.

Status

In the period between the 1940s and the 1960s, the Nile crocodile was hunted for its leather and its meat, and the species was headed towards extinction. New laws and trade regulations came into play, and Nile crocodile populations gradually got back on their feet and it is no longer a threatened species. It is thought to be between 250,000 to 500,000 in the wild today. Nile crocodile is now listed as least concern on the IUCN Red List. Today, crocodile skins come from
designated ranches and crocodile farms in Zimbabwe and South Africa. In West Africa and Central Africa, the situation is worse, as they are loosing habitat, are depleted after hunting in the 70s, and face competition from slender-snouted crocodiles (Mecistops cataphractus) and dwarf crocodiles (Osteolaemus tetraspis).

Throughout its range the Nile crocodile is targeted and killed as a man-eater. This is in many cases true, as Nile crocodiles often live in close proximity to human populations, and people are often caught and eaten by crocodiles. Many events go unreported, and it is thought that several hundred, maybe even thousands, of people are killed by Nile crocodiles each year, which is more than any other crocodile species.

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