Although the juveniles are generally restricted to eating small aquatic invertebrates and insects, they soon move onto larger vertebrates such as fish, amphibians and reptiles. Adults, however, can potentially take a wide range of large vertebrates, including antelope, buffalo, young hippos, and large cats.
Fish and smaller vertebrates often form the greatest part of their diet, however they have a reputation as being man-eaters, they have probably killed more people than all other crocodilian species combined.
There is some evidence that Nile Crocodiles in cooler countries reach slightly smaller adult sizes (4 m). There are two known population of dwarf Nile crocodiles living on the extreme limits of the species' range, in Mali and even the Sahara Desert!
Due to suboptimal conditions, adults average between 2 and 3 metres. Juveniles are dark olive brown with black cross-banding on the tail and body. This banding becomes fainter in adults.
Along with hippos and lions, crocodiles account for perhaps a few hundred deaths and disappearances each year, although exact figures are very hard to verify. Nile crocodiles will also often scavenge from carcasses, together with a number of other animals, all of which seem to tolerate each others' presence.
Several prey animals have been found wedged under submerged branches and stones, leading to reports that the crocodiles store unwanted prey here until a later date.Some claim that it is necessary for the prey to decompose before the crocodiles are able to tear portions of flesh off, but this is unlikely to be true. The flesh may become softer if the prey remains in water after death, but crocodiles will certainly avoid rotting meat. When feeding, a number of individuals will hold onto a carcass with their powerful jaws whilst twisting their bodies.The anchorage provided by the other individuals allows large chunks to be torn off for easier swallowing. Other cooperative feeding behaviour has been reported, such as the action of many animals to cordon off an area of water to concentrate fish within. A hierarchy of feeding order is often observed in such situations, with more dominant animals feeding first.
Given the wide distribution range, a number of population differences have been observed, and several subspecies proposed. These are rarely differentiated in the literature, however, and they are not officially recognised.
C. n. africanus (East African Nile Crocodile), C. n. chamses (West African Nile crocodile), C. n. corviei (South African Nile crocodile), C. n. madagascariensis (Malagasy Nile crocodile, Malagasy alligator, Croco Mada), C. n. niloticus (Ethiopian Nile crocodile), C. n. pauciscutatus (Kenyan Nile crocodile, Kenya alligator, Kenya caiman), C. n. suchus (Central African Nile crocodile).