Survived on earth
Species of alligators
Species of crocodiles
Species of gharials: fish-eating crocodilian of India and Nepal
Chambered heart (all other reptiles have 3)
Crocodiles, alligators, caiman, gharials and false gharials make up the crocodilian group, which has survived for about 200 million years. There are three families of crocodilians.
Alligatoridae: seven species including the American and Chinese alligators, and South American caimans.
Crocodylidae: 14 species including crocodiles and the false gharial.
Gavialidae: the gharial has one species only, the Indian gharial.
They eat anything from dragonflies and bats to sharks, antelopes and even buffalo.
They are cold-blooded (poikilotherms), which means they depend on heat from their environment to warm up their body instead of using food energy to heat themselves as humans and other mammals do. This makes crocodilians extremely energy efficient.
They surprise their prey. Crocodilians sit camouflaged and motionless in the water waiting for prey to come to them. Their eyes and nostrils are high on their head so the rest of their body can be hidden underwater. When prey is only a short distance away, the crocodilian will quickly snap its muscular jaws around the prey and drag it below the water to drown and eat it.
Although attacks on humans have occurred, most species of crocodilian don’t include humans as a food source in their diet. The species that have been known to hunt humans are the Nile and Indo-Pacific crocodiles. The American crocodile, black caiman and the Indian mugger will occasionally kill humans for food or to defend their nests or territories. It has been suggested that a person bending down over a water source may resemble an antelope in the eyes of a crocodile and this is why the attacks occur.
Alligators have broad, rounded snouts whereas crocodiles have narrower snouts that taper to a point. Alligators have a wider upper jaw than lower jaw so when their mouth is closed the teeth in the lower jaw are almost completely hidden and fit into sockets of the upper jaw. In crocodiles, the upper and lower jaws are the same width so teeth in the lower jaw fit outside when the mouth is closed. This makes them look like they have interlocking teeth. The skin of the crocodile is also different from the alligator. Crocodile skin is covered in sensory pits; alligators only have these pits near their jaws.
Nearly all crocodilians live in the rainforests and wetlands of developing countries which are being destroyed by development, logging and other industries. Even their nesting areas along the river are disturbed by boat traffic. So some species, such as the Nile crocodile are endangered due to habitat destruction. Poaching also reduces the crocodilian population. There is a multi-million dollar business in the illegal trade of crocodilian hides. The common caiman is the most hunted crocodilian, and makes up 60 - 80 percent of skins in the trade. However, their bony hides only receive a tenth of the price that is paid for alligator or crocodile skins.
The American alligator was one of the first animals to receive protection under the United States Endangered Species Act. They are no longer endangered but are still listed as ‘threatened.’ Steps are being taken to cut poaching and repopulate species of crocodilians by setting up crocodile farms.For more information about the status of crocodilians visit the IUCN website or the CITES website.
Yes. Some crocodiles are more aggressive than alligators. There are probably more incidents of humans being attacked by crocodiles than alligators because there are more crocodiles in existence.
This behaviour is called gaping and is done when the crocodilian is basking in the sun. Experts think that this may cool the crocodilian. However they also do this during rain and at night which suggests that gaping has a social function as well.
1. Britton, Adam. Crocodilians: Natural History and Conservation.
2. National Geographic. World of the Crocodilians. http://channel.nationalgeographic.com/crocmap/
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