The second largest of all crocodilians, the Nile crocodile (Crocodylus niloticus) is a supremely adapted aquatic predator, with a streamlined body, a long, powerful tail, webbed hind feet, and long, powerful jaws, ideally suited for grabbing and holding onto prey. The eyes, ears and nostrils are located on top of the head, allowing the crocodile to lie low in the water, almost totally submerged and hidden from prey. A special valve at the back of the throat allows the mouth to be opened to catch and hold prey underwater without water entering the throat.In addition to a good sense of smell and excellent night vision, the Nile crocodile also possess sensory pits in the scales along the side of the jaw, used to detect movement and vibrations in the water. Like all true crocodiles, the enlarged fourth tooth on the lower jaw is clearly visible when the mouth is closed, a feature which distinguishes this group from other crocodilians, such as alligators. The body of the adult Nile crocodile is a grey-olive colour, with a yellowish belly, while the juvenile is more greenish or dark olive-brown, with black cross-banding on the tail and body, which becomes fainter in adults. In general, the male Nile crocodile grows larger than the female.