Video: See the alarm warning manatees away from harm

Manatee showing propeller injuries (Image: Jeff Foott/Discovery Channel Images/Getty) Whales killed by ship strikes: (left) North Atlantic right whale cut by propeller; (right) Sei whale draped over the bulbous bow (Image: Edmund Gerstein) Manatees injured by boat collisions. Most survive collisions with smaller boats, while collisions with larger, slow-moving barges are often fatal (Image: Edmund Gerstein) Near misses at the bow of a container ship (Image: Edmund Gerstein) Advertisement Schematic of acoustic shadow ahead of a ship (Image: Edmund Gerstein) Small parametric projectors insure negligible drag on the smallest of boats (Image: Edmund Gerstein) The directional beam is only 6 degrees, which ensures only animals in the immediate path of the vessel and in imminent threat of collision are alerted (Image: Edmund Gerstein) Two different alarms, one for whales and large ships, and the other for smaller boats, designed specifically for manatees (Image: Edmund Gerstein)

A new sonic alarm could warn off whales and manatees threatened by approaching ships. Endangered North Atlantic right whales are especially at risk from collisions – only about 350 remain, and at least a third of all right whale deaths over the last decade were due to ship strikes.

A team of researchers at Florida Atlantic University believes that many collisions occur because there is region in front of moving ships where propeller sounds are blocked.

“If the ship is wide enough, the sound of the propellers is deflected off to the sides,” says Edmund Gerstein, who presents his team’s findings this week to the Acoustical Society of America.

Gerstein notes that individual manatees in Florida have been hit as many as 50 times by boats. “They seem to actually seek out the quieter zone in front of the ship as a refuge,” he says.

So he and his colleagues developed a small device to fit on the bow of a ship below the waterline, which emits sound waves focused into a narrow beam. Gerstein says that in preliminary testing of the device, manatees always changed course to avoid the approaching ships.

He hasn’t published his results however, and some remain sceptical of its efficacy, especially as it has not yet been tested on whales.

“I think its worthy of pursuit, but there is a very long way to go before this can be proclaimed as a way to prevent ship strikes in right whales,” says Scott Kraus of the New England Aquarium in Boston, Massachusetts. Gerstein says that sea tests will start next year.