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reptiles

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FIND OUT MORE. Cells 73 • Reproduction 101 • Vertebrates 102

116 Nature Nature 117

REPTILES

Rattle

VENOM

Eyesindependently move

of each other

Mitten-like feet, formed from joined,

opposing toes, give the chameleon a firm grip

HOW DO REPTILES ESCAPE FROM DANGER?Many reptiles hide, or are camouflaged to blend

in with their surroundings. Some are speedy and agile, and can scurry off at lightning speed.

Others are brightly coloured to warn predators that they are venomous.

Some lizards can break off their tail in order to escape, growing a new one

through. REGENERATION.

This group of scaly-skinned, backboned animals includes snakes, lizards, crocodiles, hard-shelled turtles, and the

tuatara, from New Zealand. Most reptiles live on land but turtles, crocodiles, and some snakes live in water. Nearly

all reptilies are equipped with senses similar to humans.

warning to large animals by shaking the Venomous rattlesnakes send out a^4 RATTLESNAKE

rattle of loose scales on their tail.

HOW DOES SNAKE VENOM WORK?Snake venom works on victims in two main ways.

The venom of snakes such as vipers causes death by damaging the prey’s body tissues and blood.

Other snakes produce neurotoxins, which attack the victim’s nervous system, paralysing the heart,

breathing system, and muscles.

The majority of snakes kill their prey with venom produced by glands in their heads.

The glands pump poison through long, pointed teeth called fangs, which bite

deep into their prey.

(^4) Snakes gather molecules with their tongues, RED-TAILED RACER
gland is very sensitive and can detect distant then transfer them to a gland on the roof of the mouth called the Jacobson‘s organ. This
prey. Some vipers can detect the body heat of prey using special pits near to their eyes.
WHAT DO REPTILES EAT?Most reptiles are active predators. Lizards hunt mainly
insects. Snakes target prey such as rodents and birds. Some snakes subdue their victims with. VENOM.
Crocodiles prey on creatures as large as wildebeest. Turtles and terrapins eat mainly fish and invertebrates.
Tortoises, which live on land, feed mostly on plants.
Forkedparticles from the air tongue picks up scent
REPTILE CLASSIFICATION

• There are around 8,000 species of reptile split into


• Snakes and lizards belong to four different orders.the same order – Squamata.
  Altogether there are more than 7,000 species of snakes
  and lizards.
  
  
  • The second-largest order, Chelonia, includes all turtles,
  
  
  • Crocodiles and their relatives tortoises, and terrapins. make up the order Crocodilia.
  
  
  • The tuatara is the last living member of its order. The rest
    died out 100 million years ago.
  
  
  
  

FANGS OUT Vipers lift their 3

model shows. At rest, fangs forward just before biting, as this

against the roof of the fangs are held the mouth.

vessels that close up quickly Fracture point has blood

to reduce bleeding

REGENERATION Tail regrows completely in less than a year

(^1) The tree skink is just one of many BEFORE AND AFTER
lizards that can regenerate their tails. Before it was lost, the end of this lizard’s tail contained
bones. Now those bones have been replaced by gristly cartilage.
WHY DO SOME LIZARDS SHED THEIR TAILS? Losing all or part of the tail is a defence mechanism
for some species of lizard. If grabbed by a predator, the tail breaks off at a fracture point, which minimizes
bleeding, and continues to wriggle, distracting the predator while the lizard escapes. Within nine months
the tail regrows, stiffened by cartilage instead of bone.
Some animals are able to regenerate (regrow) tails, limbs, or other body parts lost in
accidents or bitten off by predators. Among vertebrates (backboned animals), these species
include lizards such as the tree skink and the salamander (an amphibian).
WHICH OTHER ANIMALS REGENERATE BODY PARTS? Starfish, sponges, flatworms, and crabs can also
regrow body parts severed in accidents. Sponges have an even more amazing ability. When passed through
a fine mesh these simple multicellular animals are able to reassemble themselves. The cells seek each
other out and join back together.
(^4) Chameleons hunt by stealth, CHAMELEON
creeping forwards until their insect prey is in reach. More than half of the 85 species of chameleon
live on the island of Madagascar, including this Nosy Be chameleon.
carried in mother’s Baby crocodile^
mouth for protection from predators
The green turtle is one of just six sea-living turtle species. Its GREEN TURTLE^3
of horn. The largest sea turtle, the bony shell is covered with a layer leatherback, may reach
2.5 m (8 ft 2 in) in length.
WHAT IS THE DIFFERENCE BETWEEN A TURTLE AND A TORTOISE? Turtles live in water and tortoises live on land. Turtles from the
same scientific family as tortoises are sometimes called terrapins. Terrapins have clawed feet and live in freshwater habitats. Tortoises,
turtles, and terrapins have changed little in 200 million years. They all have bony or leathery shells.
Skinto camouflage the can change colour
chameleon or express its mood to other chameleons. Coloured cells
called chromatophores expand or contract to make this happen.
Strong flipperspropel the turtle
through the water
HOW DO REPTILES REPRODUCE? Most reptiles lay eggs, but in a few snakes and lizards,
the eggs develop inside the mother’s body so that she gives birth to live young. Crocodiles and tortoises
lay hard-shelled eggs similar to birds’ eggs. Turtles, snakes, and most lizards lay eggs with softer leathery
shells. Sea turtles lay their eggs on beaches.
HOW DO CROCODILES HUNT? The 23 species of crocodile and their relatives
are fearsome predators. Crocodiles ambush large prey. They snatch victims from the water’s
edge and drag them under to drown them. Crocodiles cannot chew, but may spin round
to break the victim’s body into pieces.
Nile crocodiles are among the CARING PARENT^3
the mother watches over the nest until the few reptiles that look after their young. Once she has laid her eggs,
babies hatch. Then she helps her offspring down to the water, sometimes carrying them in her mouth.
can be wrapped Prehensile tail
or branches for around twigs
extra stability and support
Venom gland
Hollow fangs
HOW MANY SNAKES ARE DEADLY TO HUMANS? Fewer than 10 per cent of snakes produce venom
strong enough to kill a person. Vipers produce large quantities of venom – people bitten by diamondback
rattlesnakes have been known to die in under an hour. The Australian inland taipan is thought to be
the world’s most deadly snake. Sea snakes are also highly poisonous, but they rarely bite humans.
reptiles
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