Leopard Sharks Use Their Olfactory System to Sail the Ocean

"Shark's olfactory system"

Sharks use their nose to follow their preys.

Hunting their prey is not the only way sharks use their nose: Leopard sharks use their olfactory system to sail the ocean, new study has revealed. Researchers have reached this conclusion after observing the evolution of 26 sharks that were captured in the ocean.

Californian scientists knew sharks use their noses to follow their victims in the ocean, but they were not sure whether there were other functions, as well. Consequently, they have captured 26 sharks and impaired the olfaction of 11 of them to see how quickly and efficiently they find their way in the waters.

The sharks were then taken to a distance of approximately 9 km from the shore. Scientists used various techniques to complicate sharks’ mission of getting back to the shore. They masked geomagnetic cues and they drove the boat using figure-eight maneuvers. Once they were certain the sharks could not follow them, researchers used acoustic signals to track them.

The study has revealed that the exemplars of Leopard sharks, whose olfactory system functioned perfectly reached the shore by following the correct paths in 62 percent of the cases. The 11 exemplars with modified smell sense got lost multiple times until they could finally get to the shore. In the end, scientists reported a 37 percent success rate for them.

This clearly indicates that sharks use their noses to better orient themselves in the ocean. Their olfactory system is in fact so sensitive that they can sense their prey in a ratio of one part to 10 billion. To put it in lay terms, a single drop of water in an Olympic pool tells them if there is a prey for them to hunt or not and where.

Researchers were not surprised that sharks’ nostrils have such accurate abilities. On the contrary, the structure of their noses and their brains are strong indices of their smelling capabilities.

The special cells in their nostrils, as well as the large olfactory bulbs in sharks’ brains contribute to the interpretation of the chemical substances existing in water. These chemicals help them get closer to the victim or to the shore, scientists have concluded.

In the future, researchers want to identify other possible cues that help sharks find their way in the water. They believe chemical cues play an important part, but they are most certainly complemented by other similar pieces of information. In addition, it would be interesting to understand how sharks retain and re-use chemical cues in the water to follow the correct paths.

The study was detailed in the January number of the journal PLOS ONE and was conducted by Andrew Nosal from the University of San Diego.

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