Venomous snakes inject their venom by biting, as do spiders, centipedes,
octopuses, and a few lizards and mammals. All of these
animals use their venom to paralyze or kill their prey, as well as
to defend against predators.
|This juvenile king cobra is giving off a warning
sign by hissing.
There are about 500 species of venomous snakes worldwide.
Only a few are deadly to humans. Among them are cobras, which
are found in parts of Africa and Asia.
Cobras prey on rodents, birds, frogs, lizards, snakes, and
other small animals. A cobra kills prey with venom produced in
glands at the back of its jaws, near its eyes. The venom flows
down grooves in the fangs at the front of its mouth.
The biggest cobra, the king cobra, is also the world’s largest
venomous snake. The largest king cobra ever measured was 18 feet
(5.6 m) long. However, the king cobra, like other venomous snakes,
is not eager to use its venom in self-defense. It is more likely to flee
or hide, even though its venom is strong enough to kill an elephant
with just one bite. If a predator approaches the cobra or its nest,
the cobra raises the front of its body off the ground and hisses.
It also spreads the ribs of its neck, creating a hood out around its
head. If these warnings are ignored, the snake strikes.
Some cobras spray venom at predators instead of biting them.
These “spitting cobras” have openings midway down their front
fangs. The snake squeezes venom through these openings. The
spray can hit a target up to 10 feet (3 m) away. It usually ends up
in the predator’s eyes, causing terrible pain and blindness. Sometimes,
the blindness is permanent.
Rattlesnakes, like cobras, deliver their venom with fangs.
However, a rattlesnake’s fangs are not fixed in place like a cobra’s.
instead, they are hinged. They fold back in the rattlesnake’s
mouth when it is closed. When the snake opens its mouth to
strike, the fangs spring out, ready for action.
A rattlesnake’s colors and patterns help camouflage it. If it
is spotted by a predator, the rattlesnake will try to slither away
from danger. Yet, if a predator bothers it, the rattlesnake coils up
and rattles its hollow, scaly tail sections.
Another venomous North American snake, the cottonmouth
or water moccasin, sends a warning by stretching open its whitelined
mouth. The world’s deadliest snake, the black mamba of Africa,
also warns away enemies by opening its black-lined mouth.
A recently discovered species of venomous snake in Asia is able to
change colors. This behavior has earned it the name “chameleon
snake.” Scientists think the color changes may be a warning to
Some kinds of snakes, such as coral snakes, are clad in warning
colors that advertise their venomous nature. Coral snakes are
ringed with bands of black, red, and either white or yellow. These
relatives of cobras live in North, Central, and South America,
where they prey mainly on lizards and other snakes.
Unlike snakes, the world’s two species of venomous lizards
use their venom mainly for self-defense, not hunting. The Mexican
beaded lizard and its smaller cousin, the Gila (pronounced
“heela”) monster, are both slow-moving animals that feed mainly
on eggs, baby rodents, and baby birds found in nests on the
ground. If disturbed, these lizards bite with their strong jaws.
Venom flows through the teeth from glands in their lower jaws.
The lizards chew their victims so the venom sinks inside them.
Both species have bright warning colors: They are black, with
yellow or pink uneven bands.
Vivid warning colors also adorn venomous centipedes, such
as the giant Sonoran centipede. This many-legged animal, which
lives in some of the same desert lands as the Gila monster, can
grow to be 8 inches (20 cm) long and is boldly patterned in orange
and black. It bites insects, worms, frogs, and other prey with
a pair of sharp, claw-like fangs near its head. Muscles squeeze
venom out of a gland in each fang. Like snakes, centipedes use
venom for defense as well as hunting.
Spiders’ venom also does double duty. Many spiders catch
their prey in webs, then deliver a killing bite with their fangs.
Hunting spiders lie in wait for their prey, or prowl about in
search of prey and then pounce on it like a tiger. They hang on
to their prey with their legs while they bite it, killing it with
Spiders also bite predators that attack them. Most spiders’
fangs are not strong enough to pierce predators’ skin, though,
and the venom is not strong enough to harm. A few spiders do have powerful venom. The black widow spider’s venom is more
potent than many snakes’ venom. The brown recluse spider has
venom strong enough to make a person feel ill for several days.
Like all spiders, however, these species would rather hide from
danger than bite someone.
Octopuses also would rather hide, but they will bite if they
are stepped on or attacked. An octopus uses its venom and its
strong, sharp beak to kill crabs, fish, and other prey. Most octopus
venom is not strong enough to do great harm to humans, but
the venom of blue-ringed octopuses can kill.
Different species of blue-ringed octopuses live in parts of
the indian Ocean and the western Pacific Ocean. Normally,
they wear camouflaging colors of brown, gray, and pale yellow.
But if they are disturbed, bright blue rings suddenly appear.
These rings are warning colors—and the warning is not
A greater blue-ringed octopus makes one kind of venom for
hunting and another kind for self-defense. This little octopus,
which is no bigger than a golf ball, contains enough venom to kill
about 25 people in just a few minutes. Most people harmed by a
blue-ringed octopus have either picked it up or stepped on it.
The ocean contains another group of animals that are among
the world’s most venomous animals: the cone snails. There are
about 600 species of cone snail. Most are found in tropical waters
and on coral reefs. Only a small number contain venom that is
deadly to humans.
Cone snails use their venom to kill prey, such as worms,
snails, and fish. The venom is delivered by a bite that works much
like a sting or harpoon. The snail shoots out a tube attached to
a sharp, hollow tooth. Venom flows from a gland in the snail
through this tube and into the prey. The snail uses its venom in
self-defense when it is attacked by a hungry fish.