San Diego – A group of researchers from the University of California San Diego published in the journal PLOS a finding that says leopard sharks may use their sense of smell to navigate the ocean
Researchers caught about 25 leopard sharks and transported them about 6 miles away from shore. About half of the group of sharks got their sense of smell temporally reduced by stuffing their noses with Vaseline-soaked cotton; the other half did not have their olfaction abilities jeopardized.
The scientists then released the sharks and tracked those with an impaired sense of smell to see if they had trouble finding their way back to the shore. The sharks with nose plugs appeared lost, while those without stuffed noses were able to orient themselves to be homeward bound.
“We basically kidnapped these sharks from their home and confused them for an hour on the way out. Yet, within 30 minutes of being released in the middle of the ocean, a place that they had probably never been, they [those without nose plugs] knew exactly where shore was, which was really neat.” study lead researcher Andrew Nosal, a postdoctoral researcher at the Scripps Institution of Oceanography and the Birch Aquarium in California said.
The results of the study showed that on average 62.6% of sharks with no loss of their sense of smell ended up closer to shore, in contrast, just 37.2% of those who had their nose plugged were able to find their way. The results also showed that those sharks with no loss of smell followed relatively straight paths while the group with limited sense of smell followed more tortuous paths that approximated correlated random walks.
Scientists say this ability might occur due to the ability of sensing chemical changes in the water as they swim. Nosal said they could be following gradients of plankton or amino acids that make up prey in the water. He added that the sharks’ home area likely smelled different than the open ocean several miles out to sea.
Even though the hypothesis claims chemicals smell might be the key to leopard sharks navigation system, Dr. Nosal pointed out that other sensory cues likely also play a role and that future work must determine which environmental cues are most important for navigation and how they are detected and integrated.
In 2015, a similar study was conducted at the New College of Florida. In their study researchers in Tampa Bay found similar results but instead of tracking Leopard Sharks, their investigation focused in young Blacktip sharks. The results also showed that sharks with blocked noses had trouble finding their way back to their home territory.
Source: PLOS ONE Journal