Acoustical Meeting, Nov. 10-14, 2008 in Miam...(Raton FL set out in 1991 to investigate ...)

Date:11/5/2008

Raton, FL, set out in 1991 to investigate what might be the underlying cause for these collisions. Gerstein disagreed with prevailing beliefs that manatees were just too slow and are unable to learn to get out of the way of the boats, so the boats had to slow down. He noted manatees have the "cognitive prowess to learn and remember as well as dolphins and killer whales," and when motivated "manatees can explode with a burst of power and move about 21 feet in a second." He asked some simple questions "After a manatee has been hit more than once (some have been hit up to 50 different times) why doesn't the animal learn to get out of the way?" Is it possible manatees are not aware or cannot hear the sounds of an approaching boat?

After a comprehensive series of hearing studies, Gerstein's research revealed that manatees cannot hear the dominant low frequency sounds of boats and that those sounds do not propagate well in shallow water. "Ironically, slow speed zones result in quieter and lower frequency sounds which manatees can not hear and locate in many shallow water conditions." In Florida's murky waters, where boaters and manatees cannot see each other, slow speed zones exacerbate the risks of collisions, by making these boats inaudible to manatees and increasing the transect times through manatee habitats.

Gerstein and his late colleague, Dr. Joe Blue, developed a narrowly focused alarm that emits a high-frequency signal in front of boats and other watercraft to alert manatees that may be in the path of an oncoming craft.

Gerstein has been testing this alarm in a NASA wildlife refuge where controlled studies are possible. He has reported that 100 percent of the controlled approaches toward manatees by a boat with the alarm have resulted in the manatees avoiding the boat up to 30 yards away. Only 3 percent of the manatees approached by the same boat, without the alarm, moved to avoid the boat. Gerstein notes that the alarm is tailo
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Contact: Jason Bardi jbardi@aip.org 301-209-3091 American Institute of Physics Source:Eurekalert

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