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Manatees Have "Long-Distance" Sense of Touch, Experts Say

Blake de Pastino in Crystal River, Florida
National Geographic News
January 16, 2007
 
If you ever go swimming with a wild Florida manatee, be prepared for
what might look like an amorous advance.

Renowned for their touchy-feely behavior, sea cows have been known to approach unwitting swimmers, close their eyes, open their mouths, and lean in as if busting a manatee make-out move (see photo).

But freaked-out snorkelers can relax. The behavior, scientists say, is just one example of how manatees use their uniquely developed sense of touch.

New research suggests that manatees' tactile sense is so finely tuned that the animals may experience "touch at a distance"—an ability to "feel" objects and events in the water from relatively far away.

In recent studies marine biologists Roger Reep and Diana Sarko at the University of Florida in Gainesville found that the giant mammals are covered with special whiskerlike hairs that act as sensors.

"We discovered that [manatees] have what are called tactile hairs all over their bodies, unlike most mammals, which just have whiskers on their faces," said Reep, from the university's College of Veterinary Medicine.

Together these tactile hairs form a kind of sensory array, the biologists say, possibly allowing manatees to detect changes in current, water temperature, and even tidal forces.

As for a manatee puckering up for a diver, Sarko explained, that's just the animal's way of collecting information by spreading out the hairs around its mouth to sense what it's approaching.

"Those facial hairs are actively exploring the environment around them," she said.

"But it might have liked you. I can't be sure."

Migrating in a Maze

Sarko and Reep's discovery could explain how manatees perform complex tasks, such as making long and convoluted migrations in murky water, despite having poor eyesight.

One example, Reep pointed out, is the impressive journey made by manatees in a mazelike network of waterways called Ten Thousand Islands near Naples, Florida (see Florida map).

"When you go out there for the first time in a boat and you don't know the area, you get lost in about two minutes," Reep said. "It's a really an intricate environment."

But manatees navigate the watery labyrinth every day, leaving the rivers each morning to forage in the large beds of sea grass offshore before swimming back inland at night.

"And so the question is, how do they know where they're going?" Reep said. "We're talking about relatively dark water, and we already know manatees don't have very good visual acuity anyway.

"So one of the possibilities here is that they're able to use their tactile hairs that are all over their bodies to detect the movement of water and tell them where they are in the environment, and that they're using [their sensory hairs] as a navigational tool."

Sarko agreed that this may be the case, given other observations of manatees' canny migratory skills.

"When a hurricane is coming, they get out of the area, so you do have to wonder what kind of sense they have and what they're able to detect," she said.

"But we wish we knew so much more about their capabilities when it comes to using these hairs."

Reep noted that a team at Mote Marine Laboratory in Sarasota is conducting tests with two captive manatees to determine what kinds of data the animals collect with their specialized hairs.

"By doing studies like that, you start to build up some real insight into what kind of intelligence [the manatees] are constructing with this information," Reep said.

(Learn where you can see Florida manatees in the wild with an interactive map of the Suwannee River region.)

Who Should Evolve?

In a separate study Reep and Sarko also found that manatees have more brain space dedicated to the sense of touch than other mammals do.

The research, published last month in the journal Brain, Behavior and Evolution, found that brain regions associated with touch are "especially large" in manatees—as large as or larger than in animals known to be particularly sensitive feelers, like star-nosed moles (see photo).

"That just reinforced our idea that [manatees] really are relying on their sense of touch to be able to navigate their world," Sarko said.

If sea cows are so well attuned to their environment, however, the question remains why the animals can sense something like a swimmer in the water but apparently can't detect imminent threats, particularly speeding boats.

Collisions with boats killed 86 manatees in Florida last year, the second highest toll ever recorded for such deaths.

Sarko suggested that manatees have evolved over millions of years to interpret natural forces in their environment, but they may not be well equipped to sense more modern dangers.

The threat posed by boats, she said, "is such an evolutionarily novel phenomenon that I think they haven't been able to adapt to it yet."

But as research reveals more about manatees' abilities, science may help conservation efforts evolve to better protect the animals, she said.

"Our overriding goal is to be able to understand [manatees] a little bit better and to understand how they perceive their environment," Sarko said.

"By doing that, since they haven't been able to adapt that well to us, maybe we can adapt to them a little bit better."

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