What type of animals use ultrasond?
There are a number of animals that use ultrasonic
frequencies.
The most common known is bats, who use echolocation to "see" and
to find prey. Dolphins can emit anywhere from 250hz to 220khz
(Humans can only hear lower than 20khz). Like bats, they use it as
kind of a sonar to view through murky waters.
In addition, some species of insects and amphibians can, but
that is left as an exercise to the reader to find them as there are
quite a few.