Crocodiles are the longest surviving lineage of any land animal on earth – they have survived more or less unchanged for the last 65 million years. That’s quite a long time when you think that human beings have been around for less than 200 000 years (0.3%). Crocs and their extant relatives are the last relics of the dinosaurs which dominated the world for 150 million years. They are so ancient that they are actually more closely related to birds than other reptiles.
In southern Africa we only have one of the 22 extant species from the class – the mighty and fearsome Nile crocodile. This reptile is a remarkable creature in many ways.
Relationship with man
Nile crocodiles have a tumultuous relationship with man. They see us as fair game which differentiates them from all other predators in Africa. African meat eaters big enough to eat people are actually dreadfully afraid of us and most human fatalities result from situations where the predator is extremely stressed (sick or threatened). Crocodiles are different. Perhaps because they evolved so long before us, they have no inherent fear of human beings and see us as simply another tasty animal coming down to the water to swim or drink.
This behaviour has given them a bad rap with people and we tend to view them as merciless blood thirsty killers and treat them accordingly.
Despite their fearsome reputations, crocodiles are highly attentive parents. The female, having dug a nest above the floodwater mark, will not eat for the next three months while she protects the nesting sight – a quite exceptional parental investment. The young crocs start chirping in the eggs just before the hatch and the mother then digs them gently out of their subterranean home. Then, with her utterly fearsome jaws, she picks them up gently and carries them down to the water.
How big? How long?
Nile crocodiles can grow to in excess of 1000 kilograms and just over six metres in length. Such leviathans are rare these days, with many of the largest specimens having been hunted out. The average male probably doesn’t grow much over 4.5 metres these days. Specimens have been kept in captivity for up to 60 years but it is estimated that exceptionally large wild animals can live for around a century – pretty impressive.
What do they eat?
Initially, the nippers eat insects and tiny fish. This diet then moves onto terrapins, bigger fish and eventually they’ll start ambushing hapless creatures that come to the river to drink. Crocodiles of all sizes will eat fish, particularly catfish which can grow pretty big themselves.
It would seem that the larger a crocodile gets, the less frequently it needs to eat. A big croc can eat up to half its body weight in one sitting. Some whoppers have been recorded going without food for more than a year.
Well in southern Africa, there aren’t any. The only relative on the continent is the slender-snouted crocodile which occurs in west and central Africa. Further afield, the Johnston’s crocodile occurs in northern Australia and the Morelet’s crocodile in Mexico. The most famous relative of our Nile croc is the salt water crocodile, also of northern Australia. This brute is even bigger than his Nile cousin and swims readily in the sea. He has even been recorded killing and eating sharks!
Images by Dana Allen, Olwen Evans and Kevin Van Breeda.