Predators and Threats
Due to the large size and highly aggressive nature of these apex predators, adult crocodiles have very few predators within their natural environments with the exception of occasional takings by big cats such as lions, jaguars and tigers. The smaller and much more vulnerable juveniles however, are preyed upon by a number of animal species around the world from wild pigs, dogs and large reptiles to birds of prey like eagles. Although they are common in certain areas, crocodiles are threatened throughout much of their natural ranges from hunting, habitat loss and ecological changes further down the food chain due to overfishing or water pollution, which then has an impact on them higher up the food chain.
Anatomy and Appearance
Crocodiles are large sized reptiles with thick, scaly skin that is made up of armoured, waterproof plates that both protects them from potential predators and also prevents their bodies from drying out. These scales come in a variety of colours from dull olive and green, to brown, greys and black meaning that they are very easily camouflaged in the surrounding water and vegetation. Like other crocodilian species, their eyes and nostrils are located on the very top of their broad head and snout so that they can lay in wait in the water with almost none of their bodies exposed in order to more successfully ambush prey. Their vertically flattened tails are immensely strong and are used to propel them through the water, as although they do have webbed feet, they do not use them to aid them when swimming. In order to protect them in the water, crocodiles have a special transparent third eyelid which allows them to leave their eyes open but prevents damage from the water. They also have external flaps that close off their ears and nostrils, and a special respiratory system that allows them to remain in the water for up to five hours at a time. Crocodiles range in size from the less than 2-metre-long dwarf crocodile to the 7-metre-long estuarine crocodile (also known as the saltwater crocodile or “saltie”), which is the world’s heaviest reptile weighing up to 1,000 kg.
Behaviour and Lifestyle
In the same way as other reptiles, crocodiles are not able to regulate their body temperature themselves and instead rely heavily on the heat of the sun to warm their enormous bodies up. During the hot daylight hours, they bask in the sun on the riverbanks warming their bodies up from a night of hunting. Smaller species like the dwarf crocodile (which is the least well-known of the crocodile species) are also known to climb trees in order to bask on the branches. Another way crocodiles are able to regulate their body temperature is by bobbing up and down in the water, warming in the sun on the surface and cooling themselves down beneath it. Crocodiles are highly sociable animals that remain together in large, mixed groups of adults and juveniles. However, when the mating season begins, the males become highly territorial and protect their stretch of river bank from intrusion by competitors by rearing their large heads high up into the air and and roaring at intruders. When female Nile crocodiles are attracted by these noises, the males begin to thrash their bodies around and even shoot water into the air from their nostrils.
Distribution and Habitat
Crocodiles are found in a variety of wetland habitats throughout the warmer tropical waters in the southern Hemisphere. Their inability to internally regulate their body temperature means that they rely heavily on the sun to warm their bodies up after it being cooled by spending time in the water. The American Crocodile is the largest crocodilian species in North and South America and is found inhabiting freshwater rivers and lakes, along with brackish coastal waters near estuaries and in lagoons from southern Florida, throughout Central America and into northern parts of South America. Over in Africa, the Nile Crocodile was once widespread in eastern and southern Africa but are now scarcer. They inhabit freshwater marshes, rivers, lakes and mangrove swamps. The world’s largest and most widely dispersed crocodile species is the estuarine crocodile. These formidable reptilian giants are found in river mouths and brackish swamps from the Bay of Bengal in the Indian Ocean, across to and throughout Southeast Asia and down into Australia.
Diet and Prey
Crocodiles are highly carnivorous and formidable predators and at the top of the food chain in their natural environments. Their inability to chew food has led to the development of ambush hunting techniques, and strong powerful jaws with teeth that are used to tear food apart. Young crocodiles rely heavily on fish, crustaceans, and small mammals, birds and reptiles, but as they grow larger they are able to take much bigger prey species including, deer, zebra and water buffalo. Crocodiles are often more active during the night, with some species being known to venture onto land to catch prey, livestock and in some cases, people. Due to their highly sociable nature, Nile crocodiles (which predominantly feed on fish), are known to work together in order to cordon fish off in sections of river when they are migrating. Catfish make up a large portion of their natural diets and by keeping their numbers at bay, this allows small fish species to still thrive. These fish (which would ordinarily be quickly eaten by the larger catfish) then provide food for over 40 species of bird, that in return fertilise the waters with their droppings and keep them rich with nutrients so numerous animal species can continue to thrive.