Crocodilians pt.1

Crocodilians, a group of reptiles that have been living since before the age of dinosaurs, include alligators, crocodiles, gharials, and caiman.  For over 200 million years they have adapted to changes in their habitat and food sources.  Considered highly intelligent animals, capable of complex communication, they make attentive parents and are fierce predators.  Two hundred million years ago, before dinosaurs, these reptiles were small land animals with long legs and short snouts.  As dinosaurs took over and ruled the land, crocodilians lived in the seas.  Growing in size, some as long as fifty feet, they still hunted dinosaurs on shore.  As the age of large mammals evolved to smaller species, so did the crocodilians.  They are still considered to be some of the largest species of animals inhabiting our world, today.

Scales cover the outer layer of skin on all reptiles.  The scales on crocodilians are called scutes.  With the density of bone, they are arranged in rows set into the thick, leathery skin.  This provides great flexibility while also creating a well-armored outer covering.  Belly scutes tend to be smooth, allowing for easier movement.  Scutes down the back are heavier and contain small bony disks for extra protection. 

Individual scutes are replaced as old ones wear out.  A new, larger scute grows underneath the old one which falls off when the new one is fully developed.  Skin and scute coloration blend in with the animals’  surroundings.  Patterns and color break up the animal’s outline, making it harder for predators to identify them.  Most baby crocodilians are brightly colored and grow darker as they age.

Skin & scute colors help hide a Nile crocodile in grass, American alligators on a sandy shore, and saltwater crocodiles on a rocky beach.

All reptiles are ectotherms, regulating their body heat from their surroundings.  As the sun rises each day, crocodilians come out of the water and head for shore to lay out and get warm.  When they get too hot, they may move to a shadier area, or back into the water.  Another popular method for cooling down is to sit with mouths agape, letting the breeze blow across the moist inner surfaces to draw out excess heat.  At night, they return to the water, which cools down slower than the land.

Mud wallows are another favorite place for crocodilians to spend the day.  The mud keeps the animal’s body from heating up rapidly, as well as keeping insects and parasites away from the skin.  Scutes along their tails can be flexed open to expose the skin underneath and allow excess body heat to escape.

Crocodilians have well developed senses.  Eye pupils shaped as slits can be narrowed to keep bright light from hurting the inner eye.  The tapetum lucidum, a layer at the back of their eyes, reflects light forward, allowing for excellent night vision.  Immediately behind each eye is a small ear opening that is covered when swimming.  Crocodilians have acute hearing, able to detect both prey and predator from several yards away.  They can easily hear and distinguish sounds from their own young, as well.

Nostrils on the top tip of their snouts allow normal breathing while swimming with most of their body submerged just below the surface.  Sensitive receptors can smell food at distances of over two miles.  Their tongues are wide and attached to the bottom of their mouths, so they are not used when catching prey.  Lined with taste buds, they can distinguish sweet, sour, and salt.  Crocodilians, especially in salt water habitats, accumulate salt in their bodies over time.  Special glands on the tongue allow them to rid this excess salt from their bodies.

Crocodilians are well-adapted to the habitats they live in.  We will investigate further aspects of these remarkable animals next week.