A bank-basking Nile crocodile in Murchison Falls National Park. The nile crocodile is Africa's biggest reptile by far, reaching a length of up to 6 m. The crocodiles are the last living link with the dinosaur-like reptiles of prehistoric times. Since milions of years they could survive and stand up their position as main predator in the tropical waters against the higher developed mammals. This was possible because of their low metabolic rate comparing to the energy intensive metabolism of mammals. The crocs could survive and stay active for up to 4 months without any prey.