The Sounds of Life
It’s a cold, blustery Friday afternoon in January, and the Cincinnati Zoo & Botanical Garden is all but empty. Apart from the friendly face at the gate and a few straggling golf carts manned by zoo workers, the popular attraction lacks any outward signs of activity.
Inside the zoo’s Manatee Springs exhibit, though, it’s all business. Biology professor Charles Grossman and an interdisciplinary research team from the University are spread about, taking advantage of one of the few times the exhibit isn’t packed with people. Some huddle on a catwalk behind a case of electronic gear. Others wait in the viewing area in front of giant windows.
Together, they’re performing some of the most unlikely research at the University—marine biology. Despite being situated 15 hours from the Florida coast, the team is trying to find a way to preserve the world’s manatees, whose population has dwindled to endangered levels in recent years.
The number of these gentle giants has plunged as a result of the proliferation of Jet Skis and motorboats. Last year, a record-high 95 Florida manatees were killed after being run over by boats, according to Allison McDonald, spokesperson for the Florida Marine Institute. That number translates to about 31 percent of the state’s total reported manatee deaths for the year—a record-high percentage for boat-related deaths.
What can be done about this tragedy?
Enter the University.
“The problem is this,” says Grossman. “Manatees don’t appear to hear the engines of boats. It appears that there’s some kind of an acoustic shadow generated by the boat so the sound can’t reach the front. There’s also an effect where low-frequency sounds are not projected properly on the surface.”
Add to that the fact that manatees feed on the surface, move slowly, can be hard to see in the water and are drawn to shallow areas by a taste for sea grass, and you have a recipe for carnage.
Grossman and his team—physics professor Steve Herbert, WVXU engineer Jeff Johnson, support technician Dan Bellman, mathematics professor Dave Flaspohler and six senior biology students—believe the solution may lie in mounting a sound beacon on the front of boats to warn the manatees.
So the researchers hooked up a pair of hydrophones—small speaker/transducers of the type once used to listen for Russian submarine activity—rented from the United States Navy with a tone generator/amplifier/digital recording unit built by Johnson. They pipe a variety of sounds into the manatees’ 120,000-gallon tank, hoping to find a frequency, or series of frequencies, that irritates the manatees enough to make them move away from the sound source.
While the sounds are being piped in, others observe and record every move made by the zoo’s two 1,500-pound manatees, Douglas and Stoneman.
“We put one hydrophone in one end of the tank and one in the other end,” Herbert says. “Then we switch back and forth at random.”
Watching the team at work, it’s clear that the project has taken on a life of its own. There’s no small irony in that, considering the study really didn’t start out to be a University project at all. About two years ago, Grossman’s daughter, Stephanie, was looking for a topic for her high school senior project. Father and daughter attended a talk on the plight of the manatees, and Stephanie, who was working at the zoo part time, decided she wanted to see how the animals responded to various frequencies.
They found an early champion in Terri Roth, the zoo’s vice president of animal sciences, who guided their proposal through the various zoo committees. But because manatees are an endangered species, federal approval was also necessary. And there, the process bogged down. Officials in Washington, D.C., wanted a sound engineer on the project, so Herbert came aboard. Then, officials stipulated an acoustical engineer was needed. Enter WVXU’s Johnson. Along the way, Bellman signed on to videotape the research sessions. Flaspohler recently joined the project as a statistician.
Federal approval finally came in June 2001, a full 18 months after the Grossmans’ initial proposal. By then, Stephanie had graduated from high school. Her father, however, decided to carry on the study as a senior research project for University biology students. And in September, team members began visiting Stoneman and Douglas.
At the outset, they spent much of their time unraveling manatee behavior with the help of Manatee Springs’ head keeper Eric Todd.
“I’m not a behaviorist by training,” says Grossman. “I’m primarily a bench scientist. I had this naive idea that you’d turn on a sound and if they didn’t like it, they’d run away. They don’t do that. They have all kinds of odd behaviors and you have to learn them.”
The team’s persistence paid off, though. In mid-November, the researchers began to see some results. Douglas and Stoneman seemed to respond best to multiple tones—two alternating notes similar to a British police siren.
But, Grossman says, there are plenty of unanswered questions. For example, the manatees respond to these tones, but only for about 15 minutes. Then they simply quit. Are they bored? Are they blocking the sounds? Are these really the best frequencies? And how will all of this translate to manatees in the wild?
To get a better handle on these issues, the team modified its approach at the beginning of this semester.
“Two hours is too long,” Grossman says. “We’re going to need some shorter runs during the days of the week instead of once a week to get sufficient data. This is what happens in research. You don’t know what to expect, you review the data and then change what you’re doing to get maximum response.”
At this point, no one can predict how long it may take the team to get the information they need. But Grossman wants to continue the project into the summer, and once the researchers gather sufficient data, he plans to apply for grants to fund ongoing research. Along the way, he hopes to involve more students from more disciplines.
“The more the merrier,” he says.
The afternoon’s last testing session is drawing to a close. Out in the viewing area, a high-pitched sound is barely audible through the glass. At first the manatees seem curious, turning to face the sound and even moving slightly toward it. Then Stoneman moves in the opposite direction, going into a series of graceful barrel rolls, two and then three—a maneuver that indicates he’s agitated. And Douglas retreats and flattens himself on a rock on the bottom of the tank, also a sign that the sound is having a desired effect. The team members are low-key, but happy.
As he pulls on his coat, Grossman reflects on the project and the cooperation the team has gotten from zoo personnel.
“Who’d have thought there’d be manatee research in Cincinnati?” he asks with a touch of wonder in his voice. “We’re not exactly near the ocean, you know.”