How do snakes differ from crocodiles?

Crocodiles

Family ties

It is difficult for laypeople to distinguish between all 23 species of crocodile. But the three subfamilies (alligators, real crocodiles, gavials) are relatively easy to recognize by their skull shapes.

Alligators have a fairly wide, round mouth, whereas real crocodiles have a more wedge-shaped mouth. In contrast, the mouth of gavials, who specialize in fish as a source of food, is extremely long and narrow.

There is also a striking distinguishing feature: In real crocodiles, the extended fourth tooth of the lower jaw is visible even when the mouth is closed, while in alligators it is hidden.

All crocodiles have a shell made of ossified horn plates. This is where the misleading term armored lizard comes from - although crocodiles do not count as lizards and are only distantly related to them.

Survivor

Like all reptiles, crocodiles are cold-blooded animals that adapt to the ambient temperature. They live wherever the average temperature does not drop below 15 degrees Celsius. Only alligators can handle it a little cooler.

Compared to warm-blooded animals, crocodiles have a much lower energy expenditure. Mammals convert up to 80 percent of their food into energy in order to maintain their high body temperature averaging 37 degrees Celsius. Crocodiles only need ten percent of the food for this.

In addition, they can survive weeks and months without food. So crocodiles are downright hunger artists.

Fast hunters

In the course of evolution, crocodiles have adapted perfectly to their humid habitat. They can see very well and have an extremely fine sense of smell. Submerged up to their eyes, they wait patiently for prey. Usually only the nostrils and parts of the back are visible.

With pressure sensors on their jaws, they perceive even the finest movements of the water level and thus track down their victims. Thanks to their large, muscular tails, they can jump out of the water in a flash, grab their prey with their sharp teeth and tear them down into the depths.

A flap in the throat, which can be opened or closed as required, prevents crocodiles from drowning underwater with their mouths open. The teeth of the pure carnivores are not suitable for chewing, as all crocodile species have a rigid lower jaw.

They are also unable to bite off parts of their prey. For this reason, they often turn on their own axis at a breathtaking speed in order to tear a piece of meat out of a large prey animal.

In addition, crocodiles do not have a tongue. The food is swallowed whole or in pieces and digested in the stomach. Adult crocodiles primarily hunt fish, waterfowl, and medium-sized mammals.

On land, the armored fighters seem rather clumsy. But don't let that fool you. Strong legs are sufficient for a short gallop. So caution is advised.

However, only a few species can be dangerous to humans. These include above all the Nile crocodile, native to Africa, and the Australian saltwater crocodile. They can be five to six meters long. Crocodiles usually avoid being close to humans and only attack when they feel threatened.

offspring

Female crocodiles are able to reproduce for around 40 years. A clutch consists of 20 to 80 eggs. Most crocodile species raise their offspring in nests made from plant debris. The rotting of the plants creates the heat necessary for the eggs to hatch.

It takes about 60 to 100 days for the young to be born. During this time, the parents guard the clutch. Since crocodiles do not have sex chromosomes, it depends on the incubation temperature whether females or males develop. Temperatures of 28 to 31 degrees Celsius lead to females and 31 to 34 degrees Celsius to males.

Crocodile babies that are ready to hatch make themselves noticeable by beeping sounds and free themselves from the shell. Sometimes the mother has to help out. Then she carefully takes the boys between her teeth and carries them to the water. There is a reason for so much sensitivity. Sensitive nerves at the tooth roots regulate the biting force.

cannibalism

From the beginning the young animals are on their own and must see that they prey on enough worms, crabs or beetles. Only a few young crocodiles have a chance of survival. You need to be on the lookout for birds of prey, turtles and predatory fish.

Nine out of ten boys do not experience adulthood. Therefore, as a precautionary measure, the parents give birth to an excess of offspring. Since the animal world feeds only a limited number of crocodiles in a certain habitat, the weaker younger specimens are driven away or eaten by the old.

There is more speculation than confirmed knowledge about cannibalism among crocodiles. Usually it is a matter of rival fights, which are part of the survival strategy.

It is unlikely that parents will eat their children. The adults recognize their offspring with their fine sense of smell. This usually triggers bite inhibition that spares your own children.

Social behavior

Little is known about the social behavior of crocodiles. It is undisputed that certain species hunt together, especially when larger prey animals are to be taken down.

The hunters with their terrifying teeth drive the game towards each other and grab it at different ends so that it can be torn to pieces. Everyone benefits from the collective action that they might not be able to manage on their own.

One can often observe that crocodiles lie peacefully together in a confined space to sunbathe. It is difficult to prove whether they seek proximity to their own conspecifics.

After all, researchers have found that the animals communicate using an extensive repertoire of sounds. Some of the tones are in the deep infrasound range that humans cannot perceive.

Author: Hans-J├╝rgen von der Burchard