By Blaise Jones
Sharks are masters of their environment. Every aspect of their physiology is designed to maximize their efficiency. That’s a good thing because the ocean is a tough place to live. Simply finding your way around in the murky waters can be difficult enough on its own. Yet somehow sharks are able to cross the ocean and find their way halfway around the world, all without the help of Google Maps. How do they do it?
Many times shark migrations have sensory cues that tell the sharks that it is time to go. The most obvious such indicator is a lack of prey. Many species of shark follow their food sources all of their lives, and when their prey moves further north during the summer months, the sharks follow.
However, sharks aren’t in direct contact with their prey at all times and even their vast array of amazing senses cannot keep track of every school of fish. The ocean is, after all, very big. Many sharks rely upon other external stimuli, such as feeling the change in temperature. While temperature change in coastal waters takes a long time, and temperature remains fairly constant out in open water, sharks are able to sense minute temperature changes using specialize pits located around their pectoral fins and their gills.
When the water starts changing, the shark knows it’s time to start moving.
However, reliance of their more traditional senses doesn’t help sharks find their ways across the ocean. Sharks can travel tens of thousands of miles during their lives. So how does a shark from California find its way to Hawaii?
Recent scientific studies have shown that sharks can detect weak magnetic fields. Scientists conditioned sharks via positive reinforcement (food) to swim to a specific location whenever a weak magnetic field was applied to that location. The sharks continued to swim over to that location, even when no food was provided, whenever the magnetic current was activated, proving that they could sense the magnetism.
It is theorized that sharks use their ampullae de Lorenzini to detect the Earth’s magnetic field. It’d be sort of like having a compass built into your face.
However, sharks don’t just rely on their magnetic senses for navigation. Some have the “road maps” memorized. Recent studies on tiger sharks in Hawaii have shown that they follow the same exact routes to and from deeper water and shallower water during their daily migrations. While many have speculated that they used their magnetic senses to establish these routes in their youths, some scientists believe that these sharks actually memorize the routes as they get older.
While a shark’s magnetic sense gives it the ability to determine where to go, the fact that these tiger sharks follow the exact same route and pass the exact same landmarks indicates that they are following something more precise.
Which begs the question: just how good is a shark’s memory?
“The Encyclopedia of Sharks” by Steve Parker
“Sharks: The Animal Answer Guide” by Gene Helfman and George H. Burgess
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