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Scuola elementare - en:Crocodile

Crocodiles are large reptiles that live in water. They are modern-day relatives of dinosaurs. This page can help you to learn about these living fossils. Template:Preschool Template:Complete Template:Primary

File:Croc Storyboard 12.png

How can you tell the difference between an alligator and a crocodile?

Snout

This American Crocodlile has a circle-shaped snout

• Crocs have long, narrow V-shaped snouts;
• Alligators have rounded U-shaped snouts.

Teeth

The 4th tooth of the crocodile sticks out when its mouth is closed.

• When crocs close their mouth, some teeth are still visible.
• When alligators close theirs, all teeth are hidden.

Size

• Crocodiles at birth are around 20 cm (8 inches) long - not much longer than your feet!

Saltwater crocodile: 4.3- 5.2m Nile crocodile: 4.2m American crocodile: 4.1- 4.8 m

• Depending on the species (there are 23 species!), adults may vary in size from about 1m to 7m, and can weigh more than 1.5 tons or over 3,000 pounds.
• The largest recorded crocodile was 7 meters (23 feet) long See a video of Gustav, the Giant Crocodile of Burundi (9 minutes; warning: fascinating, but may be scary; parental guidance recommended; contains some subtitles)

A crocodile skeleton.

Speed

Nile crocodile, getting its teeth cleaned by a bird (plover).

• Crocodiles are very fast over short distances, even out of water.
• The land speed record for a crocodile is 17 kilometres per hour (10.6 mph), by a galloping Australian freshwater crocodile.
• Whilst some species can gallop, the fastest way for many croc species is a "belly run". They move like a snake, wiggle their legs. and their tail whips back and forth. By belly-running, crocs can reach speeds of around 10 or 11 kilometres an hour (around 7 mph), or faster if they're sliding down muddy riverbanks.
• A human can outrun a crocodile and crocodiles being ambush predators they will not pursue you for very long.

Bite

• Crocs have extremely powerful jaws.
• Crocodiles cannot chew. They can only tear and swallow.
• Crocodiles have 64 teeth, but they are constantly being replaced. A crocodile can go through over 3,000 teeth in a lifetime.
• Each tooth is hollow, with new ones growing inside the old ones. The new tooth appears once an old one is lost.
• The salt water Crocodile has the strongest bite.

Habitat

• Crocodiles like warm environments. They do not like cold water.
• Crocodiles are found in tropical areas, such as swamps and everglades of the southeastern U.S., Central and South America, Africa, Australia, India, Pakistan, Malaysia, Borneo and Alabama .

Crocodiles mostly live in the pink, tropical zone.

Diet

Crocodiles wait... and watch. Until they are ready to attack.

• I coccodrilli sono "ambush hunters". Aspettano che i pesci o gli animali terrestri si avvicinino, per poi precipitarsi ad attaccarli. Afferrano la loro preda con le loro forti mascelle, la trascinano nell'acqua, poi rotolano più e più volte ("death roll"). Questo confonde la preda che alla fine annega. Poi il coccodrillo inizia a mangiarla.
• I coccodrilli mangiano principalmente pesci, altri rettili e mammiferi, e a volte altre creature acquatiche come molluschi e crostacei.
• Spesso si trovano pietre nello stomaco dei coccodrilli adulti. Perché?
  • Le pietre possono aiutare i coccodrilli a digerire il loro cibo.
  • Le pietre possono aiutare i coccodrilli a stare in equilibrio nell'acqua (vedi zavorra).
• I coccodrilli digeriscono tutto ciò che mangiano, comprese le ossa e le conchiglie, perché il loro stomaco è molto acido.

• Crocodiles are 'ambush hunters'. They wait for fish or land animals to come close, then rush out to attack. They grab their prey with their strong jaws, drag it into the water, then they roll over and over ('death roll'). This confuses the prey and eventually it drowns. Then the crocodile begins to eat.
• Crocodiles mostly eat fish, other reptiles, and mammals, and sometimes other water creatures such as mollusks and crustaceans.
• Stones are often found in the stomachs of adult crocodiles. Why?
  • The stones may help the crocodiles digest their food.
  • The stones may help the crocodiles to balance in the water (see ballast).
• Crocodiles digest everything they eat, including bones and shells, because their stomachs are so acidic.

Life cycle

• Le femmine di coccodrillo depongono tra le 9 e le 90 uova e le seppelliscono nella sabbia.
• I piccoli di alcune specie di coccodrillo fanno dei cinguettii nelle loro uova quando stanno per schiudersi. Questo serve per comunicare alla mamma coccodrillo di tirarli fuori dal nido di sabbia.
• Ascolta il richiamo di un piccolo coccodrillo (3 secondi).
• Le madri di alcune specie di coccodrillo portano i piccoli sulla [riva dell'acqua] tenendoli nella bocca, poi li sorvegliano finché non sono in grado di badare a se stessi.
• Template:Videoicon Video di coccodrilli del Nilo che nascono e iniziano la loro vita (National Geographic; 3 minuti)
• Il 99% della prole dei coccodrilli viene mangiata nel primo anno di vita da grandi pesci, lucertole, uccelli e ... da coccodrilli adulti.
• I coccodrilli adulti vivono fino a circa 50-60 anni; tuttavia, alcuni hanno vissuto fino a 130 anni!

• Female crocodiles lay eggs (about 9 to 90 eggs) and bury them in the sand.
• Little crocs in some species make chirping sounds in their eggs when they are about to hatch. This tells the mother croc to dig them out of the sand nest.
• Listen to the call of a baby crocodile (3 seconds).
• Mother crocs of some species carry the hatchlings to the water's edge in her mouth, then watch over them until they are able to look after themselves.
• Video of Nile crocodiles being born and starting their life (National Geographic; 3 minutes)
• 99% of the crocodile offspring are eaten in the first year of life by large fish, lizards, birds, and ... adult crocodiles.
• Adult crocodiles live to around 50 to 60 years; however, some have lived as long as 130 years!

Poems

• The Dentist and the Crocodile (Roald Dahl, Dirty Beasts)
• The Crocodile (Roald Dahl, excerpt from Dirty Beasts) sound file
• How Doth the Little Crocodile (Lewis Carroll, Alice in Wonderland)
• The Crocodile's Toothache (Shel Silverstein)
• The Crocodile (Gareth Lancaster)

Colouring-in

• Alligator and Crocodile Themed Coloring Pages (coloring.ws)
• Crocodile coloring (Google Image search)

More information

Videos

• Steve Irwin in action with "Monty" at Australia Zoo (4 mins, youtube.com)
• Crocs on film (flmnh.ufl.edu)

See also

• Famous crocodiles and alligators (Wikipedia)
• Dinosaur

External links

• Alligators & Crocodiles (EnchantedLearning.com)
• Alligators & Crocodiles Lesson Plans (National Geographic)
• Ferocious crocs (Animal Planet)
• Crocodile pre-school activities and crafts (first-school.ws)
• Crocodylus (BBC)
• Reptiles: Alligator & Crocodile (San Diego Zoo)
• Evaluate your knowledge of crocodiles (QuizMentor.com)