My Science School

Reptiles are air breathing vertebrates covered in special skin made up of scales, bony plates, or a combination of both.

They include crocodiles, snakes, lizards, turtles, and tor- toises. All regularly shed the outer layer of their skin. Their metabolism depends on the temperature of their environment.

Unlike birds and mammals, reptiles do not maintain a constant internal body temperature. Without fur or feathers for insulation, they cannot stay warm on a cold day, and without sweat glands or the ability to pant, they cannot cool off on a hot one. Instead, they move into the sun or into the shade as needed. During cooler parts of the year they become inactive. Because of their slow metabolism and heat-seeking behavior, reptiles are cold-blooded.

Reptile reproduction also depends on temperature. Only boas and pythons give birth to live young. The other species lay their eggs in a simple nest, and leave. The young hatch days to months later. The soil temperature is critical during this time: It determines how many hatchlings will be male or female. Young reptiles can glide, walk, and swim within hours of birth. Reptiles first appear in the fossil record 315 million years ago and were the dominant animals during the Mesozoic era, which lasted for 270 million years until the extinction of the dinosaurs.

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Crocodiles have a membrane that holds their fleshy tongue in place at the floor of their mouth, making it hard to move. As they mostly remain submerged in water, their tongue along with the palatal valve located at the back helps keep their throat closed, thereby preventing water from entering the airways.

Crocodile are true carnivores, eating no plant materials. In their native Africa, they prey upon and consume many large mammals, catching them when they stop to drink or cross rivers. Crocodiles do in smaller prey species with a quick snap of their powerful jaws. Larger prey might succumb to a series of deep, crushing bites.

 

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Now and then we come across news reports about a crocodile spotted or an alligator caught somewhere. So, are these words interchangeable or are they two distinct creatures? Come, let’s find out.

Though they are close relatives, crocodiles and alligators belong to two reptile groups (so, no, the words cannot be used interchangeably). At a glance, they may look alike, but on closer inspection, the differences become clear. First, the shape of the snout. Crocodiles have a pointed, V-shaped snout. The alligators, however, have wider snouts that are more U-shaped. Next, the jaw. Alligators have upper jaws that are wider than their lower jaws. So when their jaws are shut, only their upper teeth are visible. But the case is different with crocodiles. Their jaws are nearly similar in size, and so both their upper and lower teeth show even when the jaws are shut-almost making them look as if they were smiling. Alligators are less tolerant to salt water, though they can also be seen in freshwater environments. Normally, alligators are blackish-grey in colour darker than the brown- or greenish-coloured crocodiles. In 2018, researchers from Japan added something more to these differences – that “alligators tend to have shorter humerous bones in their forelimbs and shorter femurs in their hind limbs than crocodiles.”

Here’s something interesting. Both crocodiles and alligators fall under the order Crocodilla (and are called crocodilians), whicg comprises 20 to 25 species. Within Crocodilia, while true crocodiles (such as Nile crocodiles_ fall under the family Crocodylidae, alligators and their cousins called caimans come under the family Alligatoridae, and the likes of gharials (recall the thin snout and a bulbous knob at the end?) belong to the family Gavialidae.

Trivia: South Florida in the U.S. is the only place in the world where both crocodiles (the American crocodile – Crocodylus acutus) and alligators (the American alligator – Alligator mississippiensis) coexist in the wild.

 

Picture Credit : Google