| 09 January 2009
New Manatee Hearing Research
Manatees rely on their passive listening skills to get around, But boats mostly emit low- frequency sounds that manatees have trouble hearing when in murky water especially when a boat is moving slowly. Scientists from FAU have developed an “acoustic alerting device” specifically to exploit the manatees’ hearing ability. The environmentally friendly device is focused in front of the boat so that only manatees in its direct path are alerted.
A researcher at Florida Atlantic University says that motoring slowly through designated manatee protection habitats — as required by state Fish and Wildlife law — may put the meandering sea cows at greater risk of getting hacked up by your boat's motor. Says Dr. Edmund Gerstein, the university's director of marine mammal behavioral research:
"In turbid waters, where there is no visibility, slow speeds actually exacerbate the risks of collisions by making these boats inaudible to manatees and increasing the time it takes for a boat to now travel through manatee habitats."
Unlike dolphins — which use sonar to navigate — manatees rely on their passive listening skills to get around, Gerstein says. But boats mostly emit low- frequency sounds that manatees have trouble hearing.
That explains why, despite being hit once (and in some cases 50 times), the animals continue to have difficulty getting out of the way. Many Manatee hits occur in the slow zones. They can't see or hear our boats in turbid water.
In 2008, more than 300 manatees died, 90 of these were due to boat prop impact in Florida bays and inland waterways according to FWC reports.
Dr. Gerstein and his team has found a solution for alerting manatees to your presence in turbid or even clear water. They have been testing an acoustic alerting device that emits a high-frequency signal at the NASA Banana River Wildlife refuge. he has reported that, when the test boat approaches with the alarm sounding, the manatee scoots away. Without the alarm, the manatees only made an attempt to avoid the boat 3 percent of the time.
This acoustic warning device is designed to be placed in the front of the boat and only alerts manatees in the direct path of the boat.
If Dr Gerstein is right, the 30 years of establishing state laws requiring no-wake zones in high traffic manatee habitat all over Florida may have done more harm than good. Is it time to rethink manatee protection?
