For most people, the challenge would be simply taking in the sheer size of a whale shark when it swims into view, its enormous body covered in pale spots and stripes as it moves calmly through the water. But try remembering the exact arrangement of hundreds of spots and stripes across a shark that may be several metres long, swimming past you in three-dimensional space. Which spots were where? Was that small cluster near the gills there before? Did that distinctive mark sit above or below the fin? For a marine biologist, those details matter because their overall question when they see a whale shark is, “Have we seen this shark before?” And, surprisingly, the answer can be found in its spots.

Every whale shark ( Rhincodon typus ) has a unique pattern of markings on its body — almost like a human fingerprint! Around Milaidhoo in the Maldives, marine biologists photograph these patterns to identify individual sharks and build long-term records of their lives. “When we encounter a whale shark, we first give it space and let it behave naturally,” says Nairika Bharucha , Milaidhoo’s Resident Marine Biologist. The team looks for the distinctive spot pattern “behind the fifth gill slit and above the pectoral fin, all the way until the back end of the pectoral fin.” Both sides of a whale shark can be photographed because the patterns are unique on each flank, however, the left side is particularly important because it is the standard used for photo identification . The team also records the shark’s size, sex, scars, other distinctive markings, location and the date of the encounter.

“A simple photograph can become an important piece of information that helps us understand and protect these incredible animals,” Bharucha says. That photograph then becomes part of a much larger scientific process once she uploads it to the organization’s Big Fish Network portal alongside information about the shark’s behavior, location and environmental conditions. Milaidhoo’s team shares its photographs and videos with the Maldives Whale Shark Research , formerly known as the Maldives Whale Shark Research Project. Software compares the photographed pattern against whale sharks already in the database, looking for the closest match. If there is a match, the MWSR team then visually verifies the result before sending the shark’s identity and history back to the resort. The technique is known as photographic identification or “photo-ID” and it is remarkably useful because it does not require scientists to capture, tag or otherwise interfere with the animal. The method is “very reliable” for distinguishing individuals, says MSWR, and can also be used on other animals with distinctive natural markings (like manta rays, sea turtles, giraffes and leopards).

To date, MWSR has identified more than 900 individual whale sharks in its database; some have been photographed repeatedly over many years, creating detailed profiles that reveal movements, growth and even recovery from injuries. Take WS178, nicknamed Choco, for example. Choco was first identified in Baa Atoll in 2011 and has since been resighted 99 times, with its most recent sighting being once again in Baa Atoll recently. And another whale shark known as Rattehi (scientifically “WS268”), was first identified in Thaa Atoll, more than 300 kilometers from Milaidhoo. When Rattehi was first seen, he was estimated to be about 9.9 feet (3 meters) long but during his most recent sighting near Milaidhoo, he measured approximately 26 ft (8 m). Over the following decade, he has been photographed repeatedly in both atolls. “Taking photos of whale sharks resighted over years also helps us understand their growth over the years and estimate an age to length ratio,” Bharucha explains. Researchers can also document injuries and recovery. In some cases, they have watched scars become progressively less visible over repeated sightings!

The photographs can reveal how whale sharks interact with their environment. Whale sharks are filter feeders that consume enormous quantities of tiny organisms, including copepods, krill, fish eggs and larvae. Where plankton accumulates, whale sharks may follow, so by tracking individuals over time, researchers can learn more about seasonal movements, feeding areas, ocean currents and plankton blooms. It seems that for whale sharks, Baa Atoll and Hanifaru Bay can become particularly important feeding areas as seasonal monsoonal currents help concentrate plankton, attracting whale sharks as well as large numbers of manta rays. But the waters that provide food can also expose the sharks to danger. “One of the major threats to the well-being of whale sharks in our region is boat propeller injuries,” Bharucha says, explaining that whale sharks can be vulnerable to boat collisions because they often feed close to the surface. Propellers can leave serious lacerations across the dorsal surface, fins and tail.

Human interactions are another concern. Unregulated tourism can result in large groups of swimmers crowding around individual sharks and in some places, as many as 300 people may surround one animal. This may potentially block its movement and disrupt feeding. “The oceans are their homes, and we have entered their homes to view and appreciate them,” Bharucha says. “We need to ensure we do this without causing them harm and disrupting their natural behavior.” One behavior that should never be part of a whale shark encounter is touching, as human contact can damage the protective mucus layer these sharks have on their skin, potentially increasing the animal’s vulnerability to harmful bacteria and parasites. It can also cause stress and interfere with feeding and swimming. Encountering wildlife is a privilege, Bharucha reminds us, not an invitation to interact physically.

Around Milaidhoo, the 2025 observations included nine individual whale sharks; most were relatively young, immature animals measuring between about 13—30 ft (4—9 m) long. They also reflected a pattern seen elsewhere in the Maldives, with approximately 80% of whale sharks observed around Milaidhoo being male. Scientists think this skewed sex ratio may be linked to differences in habitat use, as juvenile and adult females appear to spend much of their lives in deeper offshore waters, while young males are more commonly seen in shallow, productive coastal habitats where plankton can become concentrated. Despite their enormous size, whale sharks remain surprisingly mysterious with females, in particular, being rarely seen in the shallow feeding aggregations that scientists can access. This leaves major questions about where they spend their time, where they reproduce and how their populations are connected.

And while one would think their size would make them an easy animal to study, it’s actually the opposite and that is why photographs matter. “When you spend time with them, you start to notice their individual markings, scars, and behaviors,” Bharucha says. Through programs such as Milaidhoo’s “Be a Marine Biologist,” guests may sometimes participate in the identification process when sightings and sea conditions allow, learning how researchers photograph whale sharks and how those observations eventually contribute to scientific databases. “Most importantly, we hope they leave seeing these animals not just as something beautiful but as wild animals we all have a responsibility to protect.”

Choco has a history. Rattehi has a history. Raees, another well-known whale shark first identified in 2009, has one too, including a serious injury that researchers have watched heal over time. As Bharucha puts it, “Every sighting can help us protect them and the oceans they depend on.”