2.07 Population Dynamics- Science Investigations Life Science: Investigating Animals Text-only version

Crocodiles

Scales are seen in many sizes, shapes and colors. These differences give reptiles another advantage, camouflage, the ability to blend into their surroundings and escape predators or surprise their prey. For example, the horned lizard lives in the desert, where there are few rocks and trees to offer a hiding place, but the lizard’s brown scales blend in with the desert sand, and provide camouflage, making it almost invincible. As reptiles grow, new larger scales form under the old ones. In most species the old scales are eventually shed, as a result reptiles are never without the protection of their scales.

List three functions of reptile scales.

As you watch this segment, think about how crocodiles are different from other reptiles.

What can hatch from an egg like a bird, pounce like a cat, swim like a tortoise, and leap from the water like a dolphin? It’s one of the world’s most efficient predators, the crocodile. Crocodiles are considered by many to be the last living link to the dinosaur-like reptiles of prehistoric times. Crocodiles can be found in most tropical regions of the world. They spend much of their time swimming or floating with just their eyes and nostrils barely visible above the water. Even though they can live on land, crocodiles do most of their hunting in the water or at its edge where other animals come to drink.

Crocodiles are carnivores that have several adaptations that help them capture prey. While they may not look like as if they are built for speed, the crocodile’s muscular tail helps propel it quickly through the water. They can even leap out of the water or cover short distances on the ground, at speeds of up to twelve meters per second. The crocodile uses its strong jaws to crush its prey. The long sharp teeth can be used to rip apart anything too big to be swallowed whole. Crocodiles prefer to hunt at night. While their diet is usually made up of fish, shellfish or small mammals, crocs can take down larger animals like wildebeests.

Crocodiles are as comfortable in the water as they are on land. A flap at the back of the crocodile’s mouth seals the throat and air passages so that water cannot come into its body when the animal is submerged. A thin membrane covers its eyes allowing it to see while keeping water out. Crocodiles can remain submerged for two hours or more without having to come up for air. Their heart rate slows down to accomplish this feet. While they are submerged some of the valves that control blood flow close. This diverts blood away from the lungs where it isn’t needed and sends it to the brain and other organs where the blood is essential.

Ectothermic Crocodiles

When they are not under water, crocodiles can often be found basking in the sun. As ectotherms, crocodiles rely on their environment to warm their bodies because they produce very little body heat of their own. Crocodiles will lie in the sun to warm up and move to the shade to cool down. While the crocodile lies in the sun, its scales absorb the sun’s heat. A heat sensitive camera shows that the reptile is warming up. A temperature read out displaying how the animal’s body temperature changes shows that with time the crocodile’s body temperature will increase. The scaly raised bumps along the animal’s back act like miniature solar heat collectors, and the pale yellow light on each bump shows that it is hotter than the rest of the crocodile’s body. Inside the bumps are blood vessels. As the blood circulates through the crocodile’s body, it passes through these vessels where it is heated. Then the blood continues through the rest of the body warming it as it flows.

The crocodile’s scales serve another purpose too, camouflage. The adaptation of camouflage makes it difficult for other animals to see the crocodile. Camouflage enables the crocodile to lie and wait until an unsuspecting animal comes too close to escape. Crocodiles are large animals that can grow up to six meters in length.

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