As the saying goes, “follow your nose.” And, in many cases, it’s not a half-bad mantra to adopt because, odds are, you’ll find yourself at a set dinner table or bustling restaurant hall. Baked goods and well-seasoned steaks; curry powder and blue-flames. But what about for the sake of navigation? What about throwing out the GPS for an open window? For us, that’s an improbability; it just wouldn’t work. Then again, we’re not leopard sharks.
Sharks are the sensory heat seeking missiles of our seas. (Also, I should add here that the term “sharks” is actually quite broad in a scientific sense; “sharks” are also rays and mantas. But, the for this piece, the “Jaws” connotation is of best fit.) Their sheer evolution is a testament to just how attuned a creature can be to the nuances of its environment; sharks are famous for a pressure sensory organ system called a lateral line, which enables them to acknowledge the smallest of moments. A butterfly’s wings flapping in the jet stream. And their noses aren’t half-bad, either.
Andrew Nosal, a post-doctoral researcher at California’s Scripps Institution of Oceanography and the Birch Aquarium says:
“What was amazing is that sharks that could smell find found their way back to shore no problem…all these things pointed to smell as a way to navigate and it hadn’t been demonstrated until now.”
In his recently published paper in PLOS One, Nola set out to see how sharks — leopard sharks, specifically—managed to navigate their saline realm with little in the way of physical landmarks; with no color-cues of which to paint a destination from; with little in the way of applicable guidance.
To begin, 26 leopard sharks of various ages were taken from their home and placed in a small aquarium before being released. Now, this is where things (and variables, in all matter of factness) become interesting: 11 had their nostrils filled with harmless, scent-blocking petroleum. A bit of homemade craftiness, a bout of creativity. Absolutely. The research team even went to the extent of masking their transport containers with a tarp to void solar mapping and aerating their storage waters to make sure it contained no chemical cocktails that could lead them to their prospective homecoming parties. Magnets were hung in close proximity to them with a similar mindset.. For all intent and purposes: they were completely alienated from the outside world.
About six-miles from the capture sight, 15 clear-nostrilled and 11 congested sharks found their ways back into the ocean. And, within a matter of a four-hours, those formerly described fifteen were, again, combing through the reef systems at La Jolla where they were initially “kidnaped” from; La Jolla is a widely known in the San Diego bay area for hosting pregnant leopard sharks during their summer mating seasons. As for the latter eleven, they had a bit more difficulty, circling and turning quite a bit. They were winding and weaving through the seas, while their clear-nosed kin had more linear trajectories—toward their homes.
So, data aside, what are we left with? Simply put: a somewhat concrete answer that sharks — specifically leopard sharks, that is—rely heavily on their olfactory cues in order to navigate the sea; leopard sharks, like most coastal-hugging species, posses a large olfactory bulb (an organ used for translating smells to signals) than their open-ocean ilk. And it’s likely they associate coastal run-offs and micro-gradients to trace their ways back. Well, as long as they haven’t had a horrible run-in with drugstore products, that is.
