The dolphin's intelligence, playfulness, and friendliness, its built-in smile and merry-looking eyes
have been a source of interest and enchantment
to human beings from earliest times.
Most dolphins have acute eyesight, both in and out of the water, and their sense of
hearing is superior to that of humans. Though they have a small ear
opening on each side of their head, it is believed that hearing
underwater is also if not exclusively done with the lower jaw which
conducts the sound vibrations to the middle ear via a fat-filled cavity in the lower jaw bone. Hearing is
also used for
echolocation, which seems to be an ability all dolphins have.
Dolphins are social, living in pods (also called "schools") of up to a
dozen individuals. In places with a high abundance of food, pods can
join temporarily, forming an aggregation called a superpod; such
groupings may exceed a thousand dolphins. The individuals communicate
using a variety of clicks, whistles and other vocalizations. They also
use ultrasonic sounds for echolocation. Membership in pods is not rigid;
interchange is common.
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