Snap a Shark Photo and Help Save the Biggest Fish on Earth

Tourist pictures of endangered whale sharks are helping scientists piece together mysteries of the gentle giant.

By Jason Bittel
Published 30 Nov 2017, 10:50 GMT
Tourists swim near a whale shark. Such encounters have provided valuable data for scientists studying the ...
Tourists swim near a whale shark. Such encounters have provided valuable data for scientists studying the giant fish.
Photograph by Aimee Jan

There are plenty of reasons to dislike animal selfies these days.

Along with the obvious risks in snapping photos with bears and bison, the practice can be devastating for wildlife. Earlier this year, National Geographic investigated the so-called “selfie trade" in South America, in which wild animals are captured and forced to take pictures with tourists looking for the perfect profile picture.

But there’s one very specific situation in which tourist photos may actually be helping wild animals: Increasing our knowledge of whale sharks, which were recently deemed endangered. (Read how whale sharks are disappearing, and fast.)

Though the 13-metre behemoths are the largest fish on Earth, scientists still know little about them—in part because studying the widely distributed species across tropical oceans is so challenging.

"This is indeed a very mysterious creature," says Brad Norman, a National Geographic Explorer and principal research scientist at the nonprofit ECOCEAN.

Number 459, a young male whale shark tagged with a satellite tracker, swims off Cenderawasih Bay, Indonesia.
Photograph by Dr. Alistair Dove, Georgia Aquarium

"While we are uncovering some amazing new insights into this leviathan, there is so much more we are yet to discover, including more about their breeding habits, and where they mate and have young."

Enter the tourists. Snorkeling with whale sharks (from a safe distance) has become a popular activity worldwide, from Mexico to the Philippines, and many participants are uploading their photographs to the database Wildbook for Whale Sharks.

It's a “huge force multiplier," says Alistair Dove, vice president of research and conservation at the Georgia Aquarium in Atlanta.

"To have [tourists] be our eyes and ears in the water when we’re not around is fantastic."


Each whale shark has a unique pattern of spots behind its gills, and these markings can be used to identify individuals, just like a fingerprint.

A snorkeller swims near a whale shark off St. Helena Island in the South Atlantic.
Photograph by Rafael de la Parra, Georgia Aquarium

Over the last 22 years, Norman and his colleagues have collected nearly 30,000 images of these markings in the Wildbook database—many of them taken by tourists—and used them to identify more than 6,000 individual sharks from all over the world. (Learn about how whale sharks move in mysterious ways.)

An algorithm scours the spots and compares them against all the other images to determine if there’s a match. The more images the algorithm encounters, the better it gets at obtaining IDs out of photos, even if they’re blurry or skewed.

The data has revealed seven new locations where whale sharks aggregate in large numbers, bringing the total number of known hot spots to 20, according to a new study published in the journal BioScience. What's more, Norman says that in most of these locations, there is a predominance of small, juvenile males. (Related pictures: "Biggest Whale Shark 'Swarm' Found.")

While satellite-tracking studies have revealed that individual sharks can make epic migrations of 4,800 miles or more, the new study seems to suggest this is the exception, not the rule.

In fact, far more whale sharks appear to be homebodies.

“You may see the same animal year after year in Yucatán Mexico, but you won’t see it right next door in Belize,” says Dove, a co-author on the new study. “There are remarkably few instances where animals are known to frequent more than one place.”

Such data is crucial for scientists working to protect and conserve the gentle giant, whose numbers have fallen by 50 percent in the last 75 years.

The Cautious Photographer

Citizen science is great for chipping away at these kind of global, population-level questions, says Rebecca Johnson, citizen science coordinator for the California Academy of Sciences, which created the wildlife-tagging smartphone app iNaturalist. (See National Geographic's tips for photographing wildlife.)

The pattern of spots on the skin of whale sharks is unique to each individual.
Photograph by Aimee Jan

Since its inception in 2008, iNaturalist has helped regular people contribute to all kinds of scientific advances, from the discovery of a new species of Andean poison frog to revealing the spread of invasive species, Johnson says. Users also upload their observations of whale sharks—there are 147 and counting.

But she recommends caution when approaching wild animals, especially in precarious environments such as steep cliffs.

“No piece of data is worth sacrificing your life."


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