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Crocodilians

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about crocodilians. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about crocodilians that’s not addressed in this page or the references below, please feel free to email our librarian.

Crocodilians

Questions & Answers

What are crocodilians?

Crocodiles, alligators, caiman, gharials and false gharials make up the crocodilian group, which has survived for about 200 million years. There are three families of crocodilians. 

Alligatoridae: seven species including the American and Chinese alligators, and South American caimans
Crocodylidae: 14 species including crocodiles and the false gharial
Gavialidae: the gharial has one species only, the Indian gharial

croc-caiman-face.jpgcroc-close-two.jpgcroc-pile-up.jpg

Where do crocodilians live?

They live throughout the tropical and subtropical regions of Africa, India, Southeast Asia, Australia, North, Central and South America. They live in wet habitats such as swamps, ponds, rivers, lakes and marshes.

What is the difference between a crocodile and an alligator?

Alligators have broad, rounded snouts whereas crocodiles have narrower snouts that taper to a point. Alligators have a wider upper jaw than lower jaw so when their mouth is closed the teeth in the lower jaw are almost completely hidden and fit into sockets of the upper jaw. In crocodiles, the upper and lower jaws are the same width so teeth in the lower jaw fit outside when the mouth is closed. This makes them look like they have interlocking teeth. The skin of the crocodile is also different from the alligator. Crocodile skin is covered in sensory pits; alligators only have these pits near their jaws.

 

Are crocodiles more dangerous than alligators?

Yes. Some crocodiles are more aggressive than alligators. There are probably more incidents of humans being attacked by crocodiles than alligators because there are more crocodiles in existence.

How are crocodilians adapted to an aquatic environment?

Crocodilians can hold their breath under water for a long time because they don’t move much and therefore don’t expend a lot of energy. When submerging under water, they close their ear and nostril flaps. They have a third eyelid, called the nictitating membrane that protects their eyes underwater. Vibration sensors and touch receptors help them to feel movements of prey in the water. When feeding underwater the back of the tongue acts as a valve to stop water from going into their lungs.

How long can crocodilians hold their breath underwater?

Usually they can hold their breath from 4 - 15 minutes but can remain underwater for two hours if needed and if they aren’t stressed. The record time spent underwater is eight hours in freezing conditions; this is because a cold crocodile uses less energy and oxygen so it can hold its breath longer than a warm one.

What do crocodilians eat?

They eat anything from dragonflies and bats to sharks, antelopes and even buffalo.

How do crocodiles and alligators catch their prey?

They surprise their prey. Crocodilians sit camouflaged and motionless in the water waiting for prey to come to them. Their eyes and nostrils are high on their head so the rest of their body can be hidden underwater. When prey is only a short distance away, the crocodilian will quickly snap its muscular jaws around the prey and drag it below the water to drown and eat it.

Do crocodilians hunt humans?

Although attacks on humans have occurred, most species of crocodilian don’t include humans as a food source in their diet. The species that have been known to hunt humans are the Nile and Indo-Pacific crocodiles. The American crocodile, black caiman and the Indian mugger will occasionally kill humans for food or to defend their nests or territories. It has been suggested that a person bending down over a water source may resemble an antelope in the eyes of a crocodile and this is why the attacks occur.

Why don't crocodilians eat very often?

They are cold-blooded (poikilotherms), which means they depend on heat from their environment to warm up their body instead of using food energy to heat themselves as humans and other mammals do. This makes crocodilians extremely energy efficient.

Where do crocodilians lay their eggs?

Females lay their eggs in holes they dig in the sand or in large nests made of vegetation and mud. The mother will guard the nest until she hears the cry of her babies, which break their shells with an “egg” tooth. Without the call of distress, the hatchlings may never see light, because it is the mother who digs them out of the mound of mud. She then picks up her babies in her mouth and carries them to water, breaking the remaining shells and swallowing them. The smallest of the crocodilians may lay 10-15 eggs, but larger species like the Indo-Pacific crocodile may lay 50.

Why do alligators and crocodiles often sit with their mouths open?

This behaviour is called gaping and is done when the crocodilian is basking in the sun. Experts think that this may cool the crocodilian. However they also do this during rain and at night which suggests that gaping has a social function as well.

Why are some crocodilians endangered?

Nearly all crocodilians live in the rainforests and wetlands of developing countries which are being destroyed by development, logging and other industries. Even their nesting areas along the river are disturbed by boat traffic. So some species, such as the Nile crocodile are endangered due to habitat destruction. Poaching also reduces the crocodilian population. There is a multi-million dollar business in the illegal trade of crocodilian hides. The common caiman is the most hunted crocodilian, and makes up 60 - 80 percent of skins in the trade. However, their bony hides only receive a tenth of the price that is paid for alligator or crocodile skins.

How are crocodilians being protected?

The American alligator was one of the first animals to receive protection under the United States Endangered Species Act. They are no longer endangered but are still listed as ‘threatened.’ Steps are being taken to cut poaching and repopulate species of crocodilians by setting up crocodile farms.For more information about the status of crocodilians visit the IUCN website or the CITES website.

Are there any crocodilians at the Aquarium?

The Aquarium houses two yacare caimans that were born in 1978 at Fort Worth, Texas. They were sent here in 1983 from the National Zoological Park in Washington, D.C.

Do crocodilians make good pets?

No. Crocodilians can be dangerous to keep as pets, potentially harming other pets or even people.



Facts & References

Did You Know?

Crocodilians:

  • Shed their teeth regularly.
  • Can go months without feeding as long as their body temperature remains low.
  • Roar like lions, and also snort, jaw snap and tail slap to establish courtship, dominance, territory, and aggression.
  • Communicate visually through body language and with barely audible vibrations that are transmitted to animals both in the water and on the surface.
  • Are only distantly related to the dinosaurs.
  • Are the only reptile to have a four-chambered heart (all other reptiles have a three-chambered heart).
  • Have a muscular gizzard similar to birds, which is used to grind up food prior to entering the stomach.
  • Eggs are hatched male or female depending on the their egg’s incubation temperature.
  • Mothers respond to the distress call of juveniles and defend them against predators.

References

  1. Britton, Adam. Crocodilians: Natural History and Conservation
  2. National Geographic. World of the Crocodilians. http://channel.nationalgeographic.com/crocmap/

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.

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