ARE MANATEES HARD OF HEARING?

Does poor hearing contribute to the endangered manatee's unfortunate likelihood
of being slashed by a boat propeller? Researchers Geoffrey Patton and Edmund
Gerstein think so--and they're testing the hearing of two captive manatees to
prove it.

If the theory proves correct, countless manatees might be saved simply by
outfitting boats with an underwater warning device that emits frequencies the
animals could hear, says Patton, an adjunct scientist at the Mote Marine
Laboratory in Sarasota, Florida.

Patton and Gerstein, a research biologist at Florida Atlantic University, have
trained Stormy and Dundee, two manatees at Tampa's Lowry Park Zoo, to push one
paddle when they hear a sound and to push another when they hear nothing. That
way, the researchers can determine the minimum volume manatees can hear at
selected frequencies.

``Once we've confirmed that,'' Patton says, ``we intend to introduce masking
background noise'' to find out how well the animals can pick out sounds within
the noise.

``And the third test will be in directional sensitivity,'' Patton continues.
``We want to determine how well the animals can locate where a boat may be.''

A recent census found less than 2,000 manatees living in Florida waters.
``Contact with humans has doubled the natural mortality of manatees,'' Patton
notes. ``That's why they were placed on the endangered-species list in 1973--and
why they have no hope of ever being taken off.''