Take a trip to the Ningaloo Coast of Western Australia, bring your binoculars, and if you're lucky enough to be at the right place at the right time, you might spot a famous behemoth: a whale shark, more than seven metres (23 feet) long, with a strangely shaped upper tail fin and a unique arrangement of light and dark patterning. That's Stumpy, and he's been a regular visitor to the area for over two decades.

If you manage to snap a picture of your Stumpy sighting, you can send it over to whaleshark.org, where it will become part of a huge database of whale shark records. The information on the database goes back to 1995, and the very first entry in this online library was Stumpy himself. Along with another whale shark named Zorro, these two have been visiting Ningaloo Reef regularly for 22 years. Together, they are among the longest-studied wild sharks in the world.

In order to learn about the life of an animal like a whale shark, scientists need to be able to follow them across the ocean. For many other sea creatures, this is done with GPS trackers. But it turns out the patterning on a whale shark, much like your fingerprints, is unique to each individual. This means a shark like Stumpy can be identified with a simple photo, at any point on his long migratory pathway – and that allows ordinary citizens to get in on the research.

The photo-ID library at whaleshark.org has more than 30,000 photos of over 1,000 different whale sharks. Stumpy himself is in 69 of those images. These records have unveiled a lot about the lives of the world's largest fish. "Our studies of Zorro and Stumpy are helping us to understand when whale sharks first mature and become reproductively active," says Dr Brad Norman of the Centre for Fish and Fisheries Research.

"Stumpy" the whale shark captured for photo-identification in 2015 at Western Australia's Ningaloo Reef. Image: Norman, B.M. & Morgan, D.L. 2016

Both Stumpy and Zorro are thought to have been in their teens when they were first spotted back in the 1990s, which puts them now in their thirties.

Around the turn of the century, photos showed that both sharks' claspers – the organs male sharks use to hold onto females during mating encounters – had become elongated, indicating that both of these "big boys" had reached sexual maturity. Photos from 2005 show that Stumpy's claspers had some scarring, a tell-tale sign of a mating event, so it seems there may be some baby Stumpys out there somewhere.  

Stumpy with mature claspers in 2015. Image: Norman, B.M. & Morgan, D.L. 2016

Whale sharks are gentle giants, and they have a habit of gathering regularly at known locations. These qualities make them great for tourism, and for the kind of citizen science that keeps photo records coming into the database, but it also makes them vulnerable to human activities.

These sharks are often hunted for food, and their slow growth and reproduction prevent their numbers from recovering quickly. Earlier this year, the International Union for Conservation of Nature (IUCN) changed the status of whale sharks to Endangered.

By keeping up with sharks like Stumpy and Zorro over the decades, scientists can learn about the life history of these animals, as well as where they come together for activities like breeding. "Identification and protection of these critical habitats will be imperative for the long-term conservation of this remarkable species," says Norman.

Scientists estimate whale sharks can live at least 80 years, so hopefully our friends Stumpy and Zorro will enjoy several more decades of migrating, mating and posing for photographs. Who knows? Someday, one of those photos might even come from your camera!


Top header image: Ben Brommell, Flickr