title: Olfaction Contributes to Pelagic Navigation in a Coastal Shark.
abstract: How animals navigate the constantly moving and visually uniform pelagic realm, often along straight paths between distant sites, is an enduring mystery. The mechanisms enabling pelagic navigation in cartilaginous fishes are particularly understudied. We used shoreward navigation by leopard sharks (Triakis semifasciata) as a model system to test whether olfaction contributes to pelagic navigation. Leopard sharks were captured alongshore, transported 9 km offshore, released, and acoustically tracked for approximately 4 h each until the transmitter released. Eleven sharks were rendered anosmic (nares occluded with cotton wool soaked in petroleum jelly); fifteen were sham controls. Mean swimming depth was 28.7 m. On average, tracks of control sharks ended 62.6% closer to shore, following relatively straight paths that were significantly directed over spatial scales exceeding 1600 m. In contrast, tracks of anosmic sharks ended 37.2% closer to shore, following significantly more tortuous paths that approximated correlated random walks. These results held after swimming paths were adjusted for current drift. This is the first study to demonstrate experimentally that olfaction contributes to pelagic navigation in sharks, likely mediated by chemical gradients as has been hypothesized for birds. Given the similarities between the fluid three-dimensional chemical atmosphere and ocean, further research comparing swimming and flying animals may lead to a unifying paradigm explaining their extraordinary navigational abilities.
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92037, United States of America.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Nosal
authors.affiliation: Department of Atmospheric and Oceanic Sciences and Joint Institute for Regional Earth System Science and Engineering, University of California Los Angeles, Los Angeles, California, 90095, United States of America.
authors.forename: Yi
authors.initials: Y
authors.lastname: Chao
authors.affiliation: Department of Atmospheric and Oceanic Sciences and Joint Institute for Regional Earth System Science and Engineering, University of California Los Angeles, Los Angeles, California, 90095, United States of America.
authors.forename: John D
authors.initials: JD
authors.lastname: Farrara
authors.affiliation: School of Marine Sciences, University of Maine, Orono, Maine, 04469, United States of America.
authors.forename: Fei
authors.initials: F
authors.lastname: Chai
authors.affiliation: Marine Biology Research Division, Scripps Institution of Oceanography, University of California San Diego, La Jolla, California, 92037, United States of America.
authors.forename: Philip A
authors.initials: PA
authors.lastname: Hastings
mesh_terms: D000818:Animals; D008954:Models, Biological; D012754:Sharks / Q000502:physiology*; D012903:Smell; D013550:Swimming