:33:17
even in daylight
visibility is limited underwater
:33:21
but using sonar can
be risky because the
:33:24
tell-tale clicks may reveal
your presence to predators
:33:29
so dolphins rely more on
their excellent hearing
:33:33
the best defense is to stay together
keep silent - and listen
:33:49
success in hunting is knowing
when to use your sonar
:33:53
and when to turn it off
:34:16
with its own
sonar turned off
:34:18
a killer whale moves silently
through alaskan waters - listening
:34:25
it can hear the
slightest splashing
:34:27
the very breathing
of distant prey
:34:38
a group of dall's porpoises
just up ahead
:34:44
these are among the fastest
small cetaceans
:34:47
so quick and agile they can
elude most predators
:34:55
they travel these icy waters
in groups of two to ten