Crocodiles are holdovers from the age of dinosaurs between 65 and 135 million years ago. They are certainly one of evolution's most successful products and their twenty-three species have adapted to life in many parts of the world (some in Australia have even adapted to life in salt water). There are three species in Africa, but the most common – and by far the most dangerous – is the Nile Crocodile, which can reach lengths of more than twenty feet.
I saw Nile Crocodiles in many places in Africa. There were particularly large ones in The Selous in southern Tanzania and along the Zambezi River (between Lower Zambezi National Park on the Zambia side and Mana Pools National Park on the Zimbabwe side. For some reason, the crocodiles seemed more colorful in The Selous.
Crocodiles spend a good part of the day sunning themselves along the banks of rivers. Often, their mouths gape open to vent off heat. When startled, however, they are quick to enter the water. We encountered quite a few while on a canoe safari on the Zambezi River. As we passed, most of the crocs would slide into the water and it certainly focused our attention to think of them waiting somewhere under the canoe.
Although crocodiles feed primarily on fish, they are opportunistic and will ambush virtually any animal (including humans) that ventures too close to the shoreline. While in the water, crocodiles are a model of stealth. Typically, one sees only the eyes and nose just above the water. When they spot their prey, they actually can calculate its position, then dive under the water and surprise the victim from below. Crocodiles' jaws are built solely for grabbing prey and they are not able to move their jaws from side to side as we do in order to chew. They eat by tearing off chunks of meat then swallowing it whole. In order to tear meat from larger animals, they typically grab the animal then spin their bodies (in what is known as a crocodile "death roll") until a suitable piece comes loose. Crocodiles will also stash food beneath the water under rocks or fallen tree limbs until the carcass is partially decomposed and makes for easier (and no doubt tastier) eating.
Crocodiles are a danger in virtually all sources of fresh water in Africa (parts of Lake Tanganyika being a refreshing exception). I was surprised to see them even in some very small waterholes in Zimbabwe. Crocs are capable of traveling overland for many miles at night in search of new pools of water. (They are also rather fast runners on land).
Finally, no chapter on reptiles in Africa would be complete without a mention of snakes. Africa supports a wide variety of serpents, many of them extremely poisonous. Fortunately, most snakes are as wary of humans as we are of them and they are rarely encountered. While in Africa, I saw several varieties, but the sightings were so fleeting that it was impossible to get decent photographs. One notable exception was a Black Spitting Cobra we encountered in Tarangire National Park in northern Tanzania. We were driving along one of roads in the park when we noticed a troop of mongooses acting very strangely near a termite mound. As we drove past the mound, we looked back and saw the cobra rearing back poised to strike. Mongooses, by dint of their speed and cooperative attacks, can often kill even the most poisonous snakes and the troop here was setting up for an attack. The snake, however, decided to effect a "strategic withdrawal" and soon retreated into a nearby hole. On a later trip, we encountered a poisonous puff adder crossing a road in Etosha N.P.