Sharks locate prey through inter-nostril time differences

Nature : Jayne Gardiner of the University of South Florida in Tampa and her collaborators have cleared up the mystery of how sharks exploit their sense of smell to locate prey. Conceivably, sharks could use their spatially separated nostrils to determine the concentration gradient of an odorant—the blood of an injured diver, say—and then swim up the gradient until reaching their meal. Gardiner found, however, that sharks respond instead to the difference in arrival times of an odorant at one nostril versus the other.