Back in 1902, a scientist examining the smooth, grapefruit-size brain of a manatee remarked that the organ's unwrinkled surface resembled that of the brain of an idiot. Ever since then, manatees have generally been considered incapable of doing anything more complicated than chewing sea grass. But Hugh, a manatee in a tank at a Florida marine laboratory, doesn't seem like a dimwit. When a buzzer sounds, the speed bump-shaped mammal slowly flips his 1,300 pounds and aims a whiskered snout toward one of eight loudspeakers lowered into the water. Nosing the correct speaker earns him treats. Hugh is no manatee...