We learned a lot about crocodiles at this camp because there are so many! On one boat ride, I stopped counting when I got to 16. They are fascinating reptiles and have not changed since the time of dinosaurs. Crocodiles can adapt to almost any environment and even when there is no water during the dry season here they can survive.
Crocs lay eggs on land in a nest and they incubate for 90 days. When they hatch the juveniles begin cheeping, the mother hears them, picks them up in her mouth, and carries them to the water. The temperature of the nest and where the egg is located in the nest determines the sex of the crocodile. (Strange, right!?) For instance, females crocs will hatch from the eggs deeper in the nest where it is cooler and males with hatch from the eggs higher in the nest where they are closer to the sun and it is warmer.
As far as diet, obviously crocodiles are carnivores. They will eat smaller crocodiles, impala, bush buck, and hippos. Birds are not really in danger around crocodiles because feathers are difficult to digest since crocs have gizzards (like chickens) and stones in their gizzards crush the meat they ingest. Crocodiles are often seen sitting with their mouths open and while I thought this was a sign of aggression to scare off predators (I mean – look at all of those teeth!) our guide explained that they sit facing the sun and the heat penetrates the membrane in their mouths to warm them up. In a wildlife book I read another theory about why they sit with their mouths open – that they do so in order to cool off when the sun is hot. Sorry to say I'm not sure which fact is correct.
Crocodiles are amazing creatures for another reason – they are able to slow their heart rate down to one beat per minute and stay under water for up to 45 minutes! In the dry season when there is no water for them to escape to in the heat of the day, they will slow their heart rate so that the food they eat digests more slowly. For cold-blooded animals, staying in the sun speeds up their bodily functions and they need to eat more often and try to stay cool. The slowing of the heart rate helps them survive.
These huge reptiles can weigh up to 2,200 pounds. They will wait at the edge of the water for prey to come for a drink. They’ll then lunge up out of the water to startle the prey and grab them. Then the crocs will drag them under the water in hopes of drowning them. Mostly they will eat catfish and other types of fish.
Those on the Rufiji River are Nile Crocodiles and they are colorful. I have only seen small crocodiles in the wild and really never had a chance to look at them up close. They are green and yellow with black spots on their tails. They have something like 65 teeth and an incisor on the bottom jaw sticks out.
On one of our boat rides we saw a group of crocs eating a hippo that had died of natural causes. They would bite off a piece, and roll with it in the water, mimicking how they would drown their prey. Then they would pick their head up out of the water to chew and swallow.