When it comes to marine mammals, for a long time, scientists have focused on dolphins' intelligence and manatee's brain, small (orange sized for an animal as big as a cow) and smooth which made them see these animals as being not very intelligent and incapable to fulfill difficult tasks.

But some researchers have uncovered that manatees are actually much smarter than previously thought.

Far from being slow learners, manatees seem to be as adept at experimental tasks as dolphins, though they are slower-moving and more difficult to motivate.

In lab experiments made in Florida, when a buzzer sounds, a captive manatee learned to aim the right loudspeaker from eight ones lowered into the water when it sounded in order to receive treats.

Along with other recent studies, such studies reveal a completely different nature of this animal than that we have thought.

These herbivorous mammals are so slow moving due to their size, they have no natural threats to confront and also, they conserve the energy gotten from their poor diet.

But now, they have to face a serious danger to their survival: boat propellers.

"They're not under any selection pressure to evolve the rapid-type behavior we've associated with hawks, a predator, or antelopes, a prey. They look like very contented animals that don't have very much to do all day," said Roger Reep, a neuroscientist at the University of Florida's College of Veterinary Medicine.

Florida's manatees are already an endangered species, and in 2006 at least 75 manatees have been killed in collisions with watercraft, according to the Florida Fish and Wildlife Conservation Commission.

Recent studies show the animals to hear well enough to avoid boat accidents and that's why scientists are puzzled of why manatees keep getting hit.

They may be hit while sleeping during surfacing to breathe, or they may have gotten accustomed to the sound of boats.

Reep found that manatee's brain, despite lacking folds (like in humans and dolphins), functions the same way as the brain of highly intelligent mammals.

"The brain looks just as complex internally as any other mammalian brain," said Reep.

The manatees have learned to respond to whistles and stop at underwater targets.

Scientists want to determine how well manatees distinguish colors and objects, and how sensitive their hearing and sense of touch are.

Manatees have tiny eyes and the brain region corresponding to sight is small compared to auditory and tactile, but they seem to see color, a very unusual trait for marine mammals.

However, they seem to rely on touch sense: the muzzle and body are covered with sensitive hairs that detect objects and current changes.