Snakes are elongated1
, legless, carnivorous reptiles2
that can be distinguished3
from legless lizards5
by their lack of eyelids6
and external ears. Many species of snakes have skulls7
with several more joints8
than their lizard4
ancestors, enabling them to swallow prey9
much larger than their heads with their highly mobile jaws10
. To accommodate their narrow bodies, snakes' paired organs (such as kidneys) appear one in front of the other instead of side by side, and most have only one functional11
Living snakes are found on every continent except Antarctica, and on most smaller land masses; exceptions include some large islands, such as Ireland, Iceland, Greenland, the Hawaiian archipelago, and the islands of New Zealand, and many small islands of the Atlantic and central Pacific oceans. Additionally, sea snakes are widespread throughout the Indian and Pacific Oceans. More than 20 families are currently recognized. They range in size from the tiny, 10.4 cm (4.1 in)-long thread snake to the reticulated python of 6.95 meters (22.8 ft) in length. The fossil species Titanoboa cerrejonensis was 12.8 meters (42 ft) long. Snakes are thought to have evolved from either burrowing12
lizards, perhaps during the Jurassic period.
Most species are nonvenomous and those that have venom use it primarily to kill and subdue15
prey rather than for self-defense. Some possess venom potent16
enough to cause painful injury or death to humans. The colloquial17
term "poisonous snake" is generally an incorrect label for snakes. A poison is inhaled18
or ingested, whereas venom produced by snakes is injected into its victim via fangs19
. It is worthwhile noting that certain birds, mammals, and other snakes (such as kingsnakes) that prey on venomous snakes have developed resistance and even immunity20
to certain venoms21
. Nonvenomous snakes either swallow prey alive or kill by constriction22
Feeding and diet 飲食
All snakes are strictly23
carnivorous, eating small animals including lizards, frogs, other snakes, small mammals, birds, eggs, fish, snails24
or insects. Because snakes cannot bite or tear their food to pieces, they must swallow prey whole. The body size of a snake has a major influence on its eating habits. Smaller snakes eat smaller prey. Juvenile25
pythons might start out feeding on lizards or mice and graduate to small deer or antelope26
as an adult, for example. After eating, snakes become dormant27
while the process of digestion28
Snakes can be found everywhere in the world.
Some living snakes may be 12.8 meters (42 ft) long.
Not all species kill their preys29
using venomous bites.
b b a