Ever had a friend request on Facebook from a shark? The answer is most likely no, but Facebook is a friend to one shark species: Stegostoma fasciatum, also known as the zebra or leopard shark. This shark species is relatively rare, especially in Asia where it has been heavily fished. These sharks are also popular attractions for recreational divers, inspiring scientists to devise a clever scheme for learning more about them thanks to underwater photographs posted to social media. 

“In many parts of Indonesia leopard sharks are locally extinct. They’ve been fished heavily,” says Australian shark scientist Dr Christine Dudgeon at the University of Queensland. It’s a species considered vulnerable to extinction by the International Union for the Conservation of Nature (IUCN). In Thailand too, this species is still fished, and has “largely gone from some locations,” she says.

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Many mysteries remain about leopard shark numbers, whereabouts and habits. These data gaps led Dudgeon to set up a collaborative citizen science project in Thailand where the leopard shark is sight sought after by recreational divers. The project, now two years old, represents Dudgeon’s collaboration with the Endangered Species Unit at the Phuket Marine Biological Centre, as well as Thai dive companies, recreational divers and the Thailand-based NGO Shark Guardian

And why does this species have two common names? That’s because these sharks undergo an unusual wardrobe change with age. This sleek, elongated shark switches from stripy at birth to spotted as an adult. A baby shark’s stripes begin breaking up at about one month of age, and completion of the gradual stripe-to-spot transition happens around the shark’s first birthday. Once these sharks earn their spots, their individually unique patterns give each shark a spotty fingerprint of sorts.

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Because of these unique spot patterns, the “Spot the leopard shark” project is using divers’ photographs, uploaded to their Facebook page, to catalogue the sharks. After dive enthusiasts upload photos, the scientists get to work identifying the shark as a new or already identified individual. As an added bonus, divers lucky enough to snap a new individual get to name their shark. (Leo? Lannister? Lancelot? Leandra the leopard shark? So many choices!) This shark photo album is helping scientists better understand shark numbers, lifespans, how far they travel and how well they are protected by marine reserves.

Some of Thailand’s hotspots for diving, such as the waters around Phi Phi Island, see hundreds of divers in the water every day, many with cameras, making it an ideal opportunity for harnessing underwater people power for science.

The Spot the leopard shark programme instructs divers on how to take photographs that aid identification, such as views from both sides, noting the date, location, depth, time, and sex of the shark (males have external claspers – modified pelvic fins – on their underside, something female sharks don’t have). With contributions from over 100 photographers so far, more than 200 individual sharks have been identified, aiding researchers in learning more about these rare and elusive sharks.

Top header image: Die Thukrals, Flickr