<img src=“http://upload.wikimedia.org/wikipedia/en/thumb/2/20/Nowake.jpg/230px-Nowake.jpg” style=“float:right; margin:0 0 10px 10px” width=200 alt=""/>Every year in Florida somewhere between 50 and 100 manatees are killed by boat collisions, and a lot more are injured. The government in Florida has done what it thinks it can to try and prevent these collisions by making boats slow down where manatees are likely to be found. But scientists have warned that such ‘manatee zones’ aren’t beneficial because the problem isn’t the manatees escape speed – it’s knowing there’s something to escape from. Manatees can’t hear the boats coming, and low speed boats are even harder to hear, meaning the manatee zones might actually make the problem worse.

<img src=“http://www.americanscientist.org/Libraries/images/200342613711_150.jpg” style=“float:left; margin:0 10px 10px 0” width=200 alt=""/>Manatees, an endangered species by the IUCN’s Red List, have been struggling to rebound from the hunting that once decimated their population. In 2003, a population model was released by U.S.G.S. that phad only bad news for the regions where the vast majority of manatees are found. It states, “In the absence of any new management action, that is, if boat mortality rates continue to increase at the rates observed since 1992, the situation in the Atlantic and Southwest regions is dire, with no chance of meeting recovery criteria within 100 years.” That’s because humans are responsible for 20-40% of the manatee deaths in Florida, and a good portion of those are boat-related. With the populations already struggling, the extra deaths are preventing any hopes of stable numbers.

Despite the fact that ‘Manatee Zones’ have been in effect for a few decades, the number of collisions hasn’t decreased. This is probably in part due to the rising popularity of boating in Florida waters, which proudly boast millions of boaters a year. But more over, scientists have found that manatees don’t seem to avoid boats. Marine Mammal Researcher Edmund Gerstein has been looking into the boat collision problem for years. In 2002, he wrote:

<img src=“http://upload.wikimedia.org/wikipedia/commons/thumb/6/6f/FL_fig04.jpg/250px-FL_fig04.jpg” style=“float:right; margin:0 0 10px 10px” width=250 alt="">"My colleagues and I wondered: Given that manatees have the cognitive ability to recognize danger, a fear-flight reaction and the physical prowess to evade boats, why, after an individual has been hit once, twice or three times, doesn’t it learn to avoid boats? Is it possible that manatees are unaware of the danger? Can they hear boats approaching, and if so, from how far away, from which direction and under what acoustic conditions?"

Subsequent research found that he was right – manatees simply can’t hear the boats coming. Boat engines produce a low-frequency sound that is below their hearing threshold. Moreover, that frequency gets even lower when the boats slow down, meaning the speed-reducing zones are only making it harder for manatees to hear their attackers coming.

So, Gerstein and colleagues have developed a possible solution to the problem. He’s designed an underwater alarm that would tell manatees to get out of the way. The device would produce two frequencies – 200 KLH and 220 KLH – which have been found to be highly directional and allow a manatee to pinpoint an oncoming boat so it can move away safely. When attached to the bow of a boat it can reach manatees up to 660 feet away.

The alarm is designed to work off a governor in the boat engine, and changes sound as the speed increases. While hypothetically there is a ‘fast enough’ speed at which manatees might be able to hear the boat coming on its own, Gerstein stresses that consistent sounds will make it easier for the animal to learn. If mass-produced, it could be available to the public for around $120 and reduce the need for slow-speed zones – making even the boaters happy.

Critics say that the alarm will change the natural behavior of the manatees. They say that making manatees avoid boaters instead of boaters avoid manatees is focusing on the wrong end and could have negative side effects. They also note that a manatee might need to be hit to know the sound is bad – but, in response, over 90% of manatees in Florida have propeller scars, so it’s not like they’re not getting hit already.

I think that with the situation as it is in Florida, there is no other option. We can’t sit around and wait for the millions of boaters to learn how important it is to protect these creatures – indeed, they might never. With any luck, Florida will require such a device on all boats in the near future. It may just be the last hope for the Florida Manatee.