National Geographic Sea Bird, Gulf of California — The National Geographic Committee for Research and Exploration (CRE) got to travel into the ocean realm of one of its most celebrated shark researchers last week, when it it was accompanied on a field inspection in the Gulf of California by Pete Klimley.
The recipient of 11 National Geographic grants, Klimley is known on the National Geographic Channel, PBS and YouTube as “Doctor Hammerhead” for his work with the scalloped hammerhead shark (Sphyrna lewini).
“We’ve come back to the place where I started studying hammerheads in the late 1970s,” Klimley told me as we leaned out on the forward deck of National Geographic Sea Bird, watching the sun rise out of the placid Sea of Cortez. “I have a predilection for this place, because it is where I started. I went out to a seamount here, and in what was an area the size of a small auditorium I found a huge number of hammerhead sharks, at least 500.”
Intrigued by so many sharks in one small place, Klimley wondered what they were up to. “I quickly found out that they were primarily female and that they were fighting amongst each other, and that males were then pairing with the dominant females. So that’s why they formed such big schools,” he said. “In their world, the females fight over the males.”
“They were swimming like we would drive a car down a highway.”
But why do all this fighting and pairing at that underwater mountain? “My later studies focused on that,” Klimley explained. That’s when I found that sharks could go ten miles or more out to sea in the middle of the night, and then come back without any difficulty. I fashioned a little compass sensor to record how straight they were traveling; they were swimming like we would drive a car down a highway, directly from one point to another.”
The studies of this behavior led Doctor Hammerhead to develop the theory that the sharks were using the magnetic fields of lava flows around sea mounts as highways to take them directly to where they needed to go. This also helped explain why hammerheads have such bizarre heads, to spread the shark’s sensors widely apart to better pick up minute variations in the magnetic field. (Read a PBS NOVA interview with Klimley.)
In 2002 National Geographic reported some of Klimley’s evolving theories about all this: Do Hammerheads Follow Magnetic Highways in Migration? Six years later, Klimley was part of the team that made global news with the publication of findings at a conference of the American Association for the Advancement of Science that sharks were using seamounts as well-established gathering places along fixed migration routes. (Sharks Travel “Superhighways,” Visit “Cafes”, National Geographic reported.)
Watch more of my conversation with Pete Klimley as he explains how sharks use magnetic fields to navigate their way around the ocean, even at night:
In a later post in this series I will write about my first dive into the Sea of Cortez, alongside Doctor Hammerhead, and our close encounter with the world’s largest fish, the whale shark.
- Committee for Research and Exploration (includes grant application process)
- Pete Klimley’s professional web page
- Life in the Gulf of California Hope Spot (National Geographic Voices, 2015)
- The “Aquarium of the World” at Risk (Ocean Views post by Enric Sala, 2011)
- National Geographic Expeditions Baja Cruise Itineraries
David Braun is director of outreach with the digital and social media team illuminating the National Geographic Society’s explorer, science, and education programs.
He edits National Geographic Voices, hosting a global discussion on issues resonating with the Society’s mission and major initiatives. Contributors include grantees and Society partners, as well as universities, foundations, interest groups, and individuals dedicated to a sustainable world. More than 50,000 readers have participated in 10,000 conversations.
Braun also directs the Society side of the Fulbright-National Geographic Digital Storytelling Fellowship.