Crocodilians belong to an order of reptiles that includes the crocodiles, alligators, and caimans. They are close relatives to other reptiles like snakes, lizards, tuataras, and turtles. Crocodilians are found around the world and have representing species in Africa, South and North America, Asia, and Australia. Some species are threatened or endangered as populations or entire species because of habitat loss or negative human interactions.
It is true that many of the species of crocodilians live in fresh (not salt or marine) water, like lakes, streams, and rivers. Some examples are the American alligator, which is now quite common in many rivers and marshy areas of Florida, and black caiman, which are found throughout Latin America and live in lakes or swampy areas in the tropical forests.
Crocodilians feed on a variety of other animals, including rodents, fish, birds and even very large mammals like zebras and antelope.
It is also true that some species of crocodilians live in other environments. The first obvious example is the saltwater crocodile, which gets its name because of the environment in which it inhabits. Saltwater crocodiles are native to Australia and can thrive in areas of high salinity. The crocodiles have methods to release salt from their body. They have an extra lens over their eye (present in all crocodilians) that help them to see underwater, but also protects the eye from the salt. Furthermore, they release salt through their tear ducts, hence this is where the terminology “crocodile tears” came from.
Furthermore, it is true that crocodilians have been found in the desert! There is a group of crocodiles living in the Sahara Desert in northern Africa! The crocodiles currently are described as Nile crocodiles, which is a species of crocodilians found in Africa. They tend to be very large, growing to up to sixteen feet in length! They can feed on very large mammals like antelopes, often working together to take down large prey as they drink in the water sources. The crocodilians that are found in the desert are living in various pools that are in an old river valley, left over from thousands of years ago when the land currently occupied by the Sahara Desert was a tropical forest. Quick flashes of rain during the brief rainy season each year will fill up the valley, making a deep river. As the dry season takes hold the river and pools evaporate, losing up to one inch of water a day! However, some pools are deep enough to maintain enough water to support the crocodiles.
The crocodiles living in the Sahara Desert are smaller than their other African relatives, reaching just eight feet in length. Genetic research is being conducted to determine if the Saharan crocodiles are perhaps a subspecies or even different species from the much larger Nile crocodiles. Further research is being conducted on their populations to determine if indeed the crocodiles are breeding, thus providing sustainable numbers for future generations. If a population is too small, inbreeding or inability to find a mate can occur and eventually the population will die out.
It is not clear how the crocodiles came to be in the middle of the Sahara Desert. It is possible that the individuals are the offspring of crocodiles left behind when the tropical forest became a desert. If adequate water and food (the pools are filled with catfish) were available, individuals may have survived and continued to breed. Over time they became smaller so they could survive in the small pools and eat less food. An alternative idea is that when the flashes of rain occur crocodiles are washed down the river valley from areas where crocodiles still thrive in more typical conditions. However, if this is the case, the crocodiles may still grow larger because of genetics already bred into the individuals that are displaced. Further research is needed to understand the genetics of the crocodiles and determine how long their have been isolated from other populations. If the Sahara Desert crocodiles have been separated for a long time, it suggests that they are not displaced individuals.
One other note, a few years ago a population of crocodilians was found living in caves! Research is being conducted on this population to determine if they are a different species and how they are able to live in such an unusual location.
Although we typically think of crocodilians as fresh water critters, it is true that the different species reside in a variety of habitats. Crocodilians are found in marine environments, in the desert of Africa and in caves! Crocodilians have been on Earth since the time of dinosaurs and have had a long time to adapt to many different ecosystems, allowing them to be a successful group for such a long time. This is just an example of how diverse a group of such closely related organisms can be and how much there is to learn about our natural world.
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