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Sharks are incredibly good at sniffing out prey, sometimes zeroing in on their potential snack from miles away. This accuracy comes from their keen sense of smell, which can detect delays in smell no more than a second long. Whenever they notice a lag, sharks will alter their course until the scent becomes more consistent.
This evidence flies in the face of what used to be the popular view: It was believed that sharks detected smells based on the concentration of odor molecules hitting one nostril as compared to the other. However, studies based on this hypothesis showed that relying on molecule concentration can be deceptive:
"There is a very pervasive idea that animals use concentration to orient to odors," stated Jayne Gardiner of the University of South Florida. "Most creatures come equipped with two odor sensors - nostrils or antennae, for example - and it has long been believed that they compare the concentration at each sensor and then turn towards the side receiving the strongest signal. But when odors are dispersed by flowing air or water, this dispersal is incredibly chaotic."
Gardiner's findings may explain the peculiar orientation of the hammerhead. Their wide, flat heads may allow them to pick up on smells far better than other shark species.
"If you consider an animal encountering an odor patch at a given angle, an animal with more widely spaced nostrils will have a greater time lag between the odor hitting the left and right nostrils than an animal with more closely spaced nostrils," Gardiner explained. "Hammerheads may be able to orient to patches at a smaller angle of attack, potentially giving them better olfactory capabilities than pointy-nosed sharks."
Source: Science Daily