Olfaction may contribute to shark ocean navigation, likely based on their ability to sense chemical changes in the water as they swim, according to a study published January 6, 2016 in the open-access journal PLOS ONE by Andrew Nosal from UC San Diego and colleagues. Little is understood about how sharks navigate¹ straight paths between distant sites in the ocean. The authors of this study used shoreward navigation by leopard² sharks to test whether olfaction contributes to ocean navigation. About 25 leopard sharks were captured alongshore. About half had their sense of smell temporarily impaired³, and then they were transported 9 km offshore⁴, released, and acoustically⁵ tracked for approximately four hours each. 

 

On average, tracks of control sharks, with no impairment of their sense of smell, ended 62.6% closer to shore after the four hour period, following relatively⁶ straight paths. In contrast, tracks of sharks with impaired smell ended 37.2% closer to shore, following significantly more tortuous⁷ paths. The authors suggest their study experimentally demonstrates that olfaction contributes to ocean navigation in sharks, likely a result of their ability to sense chemical gradients in the water. 

 

Dr. Nosal adds: "Although chemical cues apparently⁸ guide sharks through the ocean, other sensory⁹ cues likely also play a role. Future work must determine which environmental cues are most important for navigation and how they are detected and integrated."

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