UF Veterinarians, Engineers Team Up On New System To Save Manatee Lives

May 22, 2003

GAINESVILLE, Fla. — Manatees and boaters, two groups perpetually at odds, might soon find themselves on the same wavelength, thanks to the equivalent of the manatee pick-up line.

Because the placid sea cows flock to shallow water and swim slowly, averaging 3 to 5 miles per hour, they are particularly susceptible to collisions with boats, especially around holidays such as Memorial Day that are popular with recreational boaters. Such hits account for the main reason manatees die in the United States. Many others suffer severe cuts and other injuries.

Now UF researchers from the colleges of Veterinary Medicine and Engineering have developed a sophisticated acoustical system used to assess how manatees react when vocalizations from their brethren are taped and played back on underwater speakers. Preliminary results show the technology, designed to save manatees’ lives and boaters headaches, has the potential to accurately pinpoint manatees’ location. That could lead to devices that would signal boaters that manatees are present, enabling them to adjust their speed on an as-needed basis. Currently, slow-speed zones – a source of frustration for many boaters – are fixed in Florida waterways where manatees reside.

Deke Beusse, director of UF’s Marine Mammal Medicine Program, and Chris Niezrecki, an assistant professor in the College of Engineering who directs one of the college’s acoustics laboratories, are fine-tuning their methodology at Florida locations such as Blue Springs and Homosassa Springs State Park where many of the animals live in quasi-captive conditions. The researchers are documenting how the mammals react when vocalizations from other manatees are played to them via underwater speakers. The manatees’ calls are somewhat of a cross between a squeaky swing and a shrill chirp.

“We have found that animals vocalize more than originally thought in a quasi-captive environment,” Beusse said. “We’ve also found that they increase vocalizations when the sounds of other manatees are played back to them.”

Eventually, the UF team hopes their technology will be able to pick up the sounds manatees make through the use of hydrophones located in the channels of heavily used waterways. As soon as sounds are detected, broadcast vocalizations would immediately cease so that manatees wouldn’t suddenly head toward boat traffic.

“Then by alerting boaters, either through a blinking light or a radio signal, we could let them know where the manatees are, so that they can slow down or continue at normal speeds if manatees aren’t in the area,” Beusse said.

The work is highlighted in the May issue of BoatUS, a publication of the Boat Owners Association of the United States.

“I’ve never met a boater who wanted to hurt a manatee,” Lydecker said. “What boaters hate is all the regulation. The one area where it seems people can agree on is the use of technology to solve this problem.”

Manatees, listed as an endangered species by the federal government since 1967, are large, gentle mammals that are entirely aquatic. Human activities are the major threat to their survival through boat-related injuries and deaths, habitat loss or degradation, and in some countries, hunting, according to the U.S. Geological Survey’s Sirenia Project. The number of manatee deaths attributed to boat collisions continues to rise. Last year, the survey reported a record number – 95 – died. The U.S. Geological Survey, or USGS, estimates only about 3,000 manatees remain in existence.

“More manatees fall victim to our recreational and boating needs each year, and this year will be no exception, as the number through April 30 is already at 24 animals,” said Bob Bonde, a USGA researcher. “Most will die in the warmer summer months as more boats compete to get out on the water to take advantage of nice weather. Anything that can be done to simultaneously encourage participation among boaters and save manatee lives should be of interest to all who value our endangered species while at the same time appreciating the importance of the boating industry in this state.”

Researchers have only been in the field for a few months and are still documenting their findings. So far they’ve made trips to Blue Springs and to Homosassa Springs, and each trip requires roughly two weeks to process the highly technical data they gather. The team has measured the number of sounds that emanate naturally from the manatees in these locations and compared that information with how the animals respond when the sounds of other manatees are broadcast underwater.

“We were getting approximately two calls for a single manatee per five-minute period,” Niezrecki said. “When we started to broadcast vocalizations, the rate of vocalization approximately doubled.”

On a recent trip to Homossassa Springs on Florida’s west coast, UF engineering graduate student Richard Phillips monitored the power supply equipment – which included two amplifiers, a recorder and a computer – while Niezrecki swam underwater transporting equipment from place to place. Information from the underwater hydrophones and speakers lit up Phillips’ laptop throughout the day.

Whenever manatee sounds were broadcast, most of the nine resident sea cows responded by rapidly swimming to the speaker site, circling it intensely.

“Look at that, they’re going crazy,” Beusse said.

The project began with a $15,000 grant from the Florida Legislature and has continued with $215,000 from UF’s Marine Mammal Medicine program.

Although research has been conducted on manatee vocalizations in the past, never before have scientists attempted to evaluate the effects of broadcasting sound to manatees, Bonde said.

“Scientifically, the UF project is significant because it raises questions about how manatees hear and at what frequencies they are able to detect sound,” Bonde said.

The next phase of the UF team’s work will involve testing in a large area within the Indian River on Florida’s west coast. Researchers will then attempt to determine from what distance the manatee sounds can be detected and from what distance manatees can distinguish other manatee sounds.

“Then we will work out the technical aspects of warning boaters with lights, radio and through depth finders,” Beusse said, adding that theoretically, various state agencies would determine the best locations for using the devices.