This week’s episode is all about crocodiles, alligators, and their relations. Thanks to Damian, John Paul, and John Paul’s son for the recommendation!

A Chinese alligator:



It’s easy to tell alligators and crocodiles apart. Just ask them to stand side by side, then lean over and look down to see the head shape. Broad-headed alligator on left, slender-headed crocodile on right:



Saltwater crocodile. Look, I'm only going to say this once: DO NOT SIT ON A CROCODILE OKAY THAT IS JUST DUMB AND YOU WILL GET EATEN ONE DAY IF YOU KEEP ON DOING IT



A gavial:



Black caiman:



Further reading:

A newly discovered difference between alligators and crocodiles

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

This week’s episode is about crocodiles and alligators, and their relations. Thanks to a couple of different listeners for the suggestion, Damian and John Paul, and John Paul’s son. We’ve touched on crocodiles before in a couple of different episodes, including episode 53 about dragons, but alligators have barely had a mention.

Crocs and gators aren’t actually that closely related, but both are members of the order Crocodilia. This order also includes caimans and gavials, as well as some verrry interesting extinct members.

Crocodilians are amphibious reptiles. They spend much of their time in the water but also spend time on land. They breathe air, lay eggs, and depend on air or water temperature to regulate their body temperature. All crocodilians have evolved to take advantage of their watery habitat: long tails that are flattened laterally, eyes and nostrils close to the top of the head, short legs with webbed toes, and a flap at the back of the mouth that keeps water from flowing into the throat and airways. They can stay underwater for at least 15 minutes without needing to surface for air, and some individuals can stay underwater for close to two hours under the right conditions.

Crocodilians have thick protective scales on much of the body, called scutes, strengthened by osteoderms, or bony plates. Some scutes contain sensory receptors that sense touch, heat and cold, chemical stimuli, and especially the movement of water. Crocodilians see well even in darkness and have good hearing and smell too.

Some mother crocodilians lay her eggs in holes in the sand, but most build a nest out of vegetation. As the vegetation rots, it generates heat that warms the eggs. If the temperature in the nest is constantly above 90 degrees Fahrenheit, or 32 Celsius, more babies develop into males. If the temperature is cooler than that overall, more babies develop into females.

The mother protects the nest, which is usually near her den. Sometimes several females nest close to each other to help each other protect the nests. When her babies start hatching, the mother crocodilian digs them out of the nest since they aren’t strong enough to do it themselves, and carries the babies to water where they are safer. She also protects them for a while after they hatch. This is important, because baby crocodilians are vulnerable to predators—including adults of their own species.

Different species of crocodilians communicate in different ways. Some roar or bellow, some hiss, grunt, slap the jaws shut loudly, splash the head or tail in the water, or blow bubbles. Males often growl infrasonically—a sound humans feel more than hear, and which can cause the water around the male to shiver. That’s creepy. Baby crocodilians still in the egg will mimic tapping sounds, and yelp or grunt to let their mother know when they’re hatching.

One interesting thing about crocodilians is the way they walk. Most of the time a crocodilian walks with its belly touching the ground and its tail dragging. This is called the low walk. But unlike most other reptiles, most crocodilian species have ankle joints that allow it to raise its body up off the ground and walk like a mammal,