Amanda has taught high school science for over 10 years. She has a Master's Degree in Cellular and Molecular Physiology from Tufts Medical School and a Master's of Teaching from Simmons College. She is also certified in secondary special education, biology, and physics in Massachusetts.
What Are Crocodiles?
Over 200 million years ago dinosaurs ruled the Earth. Gigantic reptiles reigned supreme with little competition from other species. That is until about 65 million years ago when the last of the dinosaurs went extinct. Scientists are still puzzled by what caused this mass extinction, but even though all true dinosaurs died out some of their relatives have survived today.
Crocodiles are the closest descendants of the dinosaurs with some fossils dating back to 200 million years ago. Crocodiles are the largest reptiles on Earth today with some weighing over 2,000 pounds.
All crocodiles are semi-aquatic and dwell in marshes, rivers, and even oceans. They can be distinguished from their alligator relatives by their narrow snout. Crocodiles also sport a toothy grin. Their upper and lower jaws are the same width, causing their teeth to show when their jaws are shut. Alligators have a wider upper jaw which allows the lower teeth to fall into place, hidden from view.
Crocodiles live in tropical waters around the globe in the Americas, Africa, Asia, and Australia. Today, we're going to look at characteristics of several species of crocodiles and their habitats.
Nothing embodies the Everglades of Florida quite like crocodilians. The American crocodile is a crocodile living in the shores of the Americas, from Northern South America through the Caribbean, Mexico, and Southern Florida in the northern end of its range. This massive reptile can grow to be about 15 feet long and weigh up to 2,000 pounds, about the weight of ten refrigerators.
Although many people go for an afternoon at the beach in Florida, the American crocodile prefers a more swampy habitat. It lives in brackish waters, a mixture of saltwater and freshwater on the coast, as well as mangrove swamps, lagoons, rivers, and estuaries.
During the day crocodiles can be seen basking on river banks. Like other reptiles they are ectothermic, meaning they use ambient heat to regulate their body temperature. Basking in the sun warms them after a cool night. If you see a crocodile with an open mouth, don't take it as a sign of aggression. This characteristic stance is actually a method of regulating their body temperature.
Along the banks of one of the longest rivers in the world lives the Nile crocodile. The Nile River runs throughout Africa from below the equator in Burundi north to the Mediterranean Sea. The Nile crocodile can be found throughout the lower Nile Basin in sub-Saharan Africa as well as the northeast coast of Madagascar. Similarly to the American crocodile, the Nile crocodile enjoys rivers, freshwater marshes, and mangrove swamps. Unlike the American crocodile, the Nile crocodile prefers freshwater environments and isn't usually found in the brackish or saltwater estuaries that the American crocodile calls home.
Although it is quite long, measuring 16 feet from head to tail, this crocodile, on average, only weighs about 500 pounds, about a fourth of the weight of the American crocodile. But don't let its weight fool you; coming across a Nile crocodile in the wild isn't the best situation. These crocodiles are famed man-eaters and are responsible for about 200 deaths per year. As you might be thinking, these animals aren't picky eaters. They primarily eat fish but will eat anything smaller than them that crosses their path, including other crocodiles!
Catch a flight to India, Southeast Asia, or northern Australia, and you'll get a glimpse of the largest crocodile in the world, the saltwater crocodile, or 'salty' as locals refer to them. Although the average size is 17 feet and about 1,000 pounds, some specimens have been recorded to be 23 feet long and weigh 2,200 pounds.
Like their name implies, these crocodiles can spend most of their time in oceans of full salinity, but they also can live in freshwater or brackish water. With their aquatic lifestyle, they are fairly good swimmers and have even been seen surfing ocean currents drifting far out to sea. Scientists think their range can extend dozens of kilometers out into the open ocean not because they are such strong swimmers, but because they are able to let the ocean currents carry them, limiting their aerobic expenditure. However, even the strongest swimmers need to take a break. All salties must come to land to bask and lay eggs.
These animals are fierce and will dine on anything smaller than themselves. They grab land mammals with their large teeth, dragging them into the water to drown them before thrashing their head to pull apart the meat. Crocodiles' jaws aren't made for biting off pieces of prey; they must tear their food apart with force if they cannot swallow it whole. Humans aren't a natural source of food, but salty attacks do happen. And terrestrial animals aren't all that's on the menu. Birds, fish, and even sharks can become food for this reptile.
Crocodiles are ancient reptiles that live a semi-aquatic lifestyle in oceans, rivers, estuaries, marshes, and mangroves. The American crocodile lives from the northern coast of South America through the southern tip of Florida in the Everglades. The Nile crocodile lives in the freshwaters of the Nile Basin of sub-Saharan Africa, and the rivers, streams, and mangroves of Madagascar. The saltwater crocodile is the largest crocodile on Earth and lives in India, Southeast Asia, and Australia. It can live entirely in saltwater and has been known to eat large prey from the ocean and land.
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