Nile crocodile

An old design, still working

There are around 16–18 species of true crocodiles in the tropics of Africa, Asia, Australia and the Americas, living in rivers, lakes, swamps and mangroves. The best known is the Nile crocodile, Crocodylus niloticus, of sub-Saharan Africa; large males reach 4–5 m and weigh several hundred kilograms. Saltwater crocodiles of Asia and Australia are even bigger. Crocodilians as a group have existed for more than 80 million years.

Your eyes, ears and nostrils would sit on top of your head, so you can watch and breathe while almost submerged. Small sensory pits on your jaws detect tiny pressure changes in the water. A flap at the back of your throat lets you open your mouth underwater without drowning.

Ambush and patience

Crocodiles are ambush predators. Young ones eat insects, frogs and small fish; adults take fish, birds and mammals, from antelopes to zebras and wildebeest crossing rivers. Measurements of saltwater crocodiles recorded some of the highest bite forces ever measured in living animals, though the muscles that open the jaws are weak. Large prey is drowned and torn apart by spinning, the so-called death roll.

As a cold-blooded reptile, you would regulate your temperature by basking on banks, often with your mouth open, and slipping into water to cool down. Big crocodiles can go many months without eating.

Careful parents, long lives

Female Nile crocodiles lay about 40–60 eggs in a nest dug into a sandbank and guard it for around three months. Nest temperature determines the hatchlings’ sex. When the young call from inside the eggs, the mother digs them out and may carry them to water in her mouth. Still, monitor lizards, birds and fish eat most hatchlings. Adults have few enemies besides hippos, lions and humans, and can live 50 years or more. Nile crocodiles are also responsible for numerous attacks on people each year.