Field guide training: Reptiles – Part 5

Crocodiles are also known as living fossils, because they have been traced back for 135 million years – and since then the giant reptiles have not changed much. Among scientists this is referred to as a highly conserved development.

The order Crocodilia involves only one family, which includes 21 species. These species can be found in tropical and subtropical regions all over the world. The Nile crocodile is the only species which exists in Southern Africa. As soon as you approach water bodies which may be a habitat for crocodiles you should be very careful. In water as well as on land crocodiles can reach an enormous speed over a short distance. Most people who have been injured by crocodiles were not aware of the danger and came to close to the water body.

Adult Nile crocodiles can weigh up to 1000 kg and reach a length of over 6 meters, of which 40 % is represented by the thick tail. Other characteristics are thick scales made of horn and long and sharp rows of teeth.

Crocodiles are carnivores and either hunt prey which they have selected or feed from carrion. This behaviour fulfills an important role in the ecosystem because crocodiles remove carcasses from the water and eliminate old or injured animals from a herd which will support the health condition in the animal herd in the end.

The mating season of crocodiles starts in May. They reach sexual maturity at the age of 12 or 15 years. After the end of the mating season, which is the time when males show very distinctive hierarchy behaviour, the females move on land to look for a place where they can lay their eggs (often a sunny and sandy area). The females dig a hole and lay between 16 and 80 eggs which they cover with soil and plant material. The microclimate which surrounds the eggs is very important for the success of the reproduction. If the temperature differs to much from the ideal temperature, the eggs will die. The female will dig out the eggs and carry the young crocodiles in their mouth, when breeding was successful. The mother and her offspring will stay close to each other for the next 6 to 8 weeks. Due to the high number of enemies (e.g. hyenas, snakes, otters) only one out of 50 eggs survives.

Good to know: Even though alligators do not exist in Africa it is good to know the difference between an alligator and a crocodile. Both species can be found on the American continent. Despite their similar appearance there are some characteristics which make it simple to distinguish both species. The lower and upper jaw of crocodiles for example is the same size, which means teeth from both jaws are visible. Another characteristic is the fourth canine tooth of the lower jaw sticking out in front of the upper jaw. In contrast the upper jaw of alligators is bigger than the lower jaw, so that only the teeth from the upper jaw are visible.