Connecting the Spots – Whale Shark Fun Facts

According to National Geographic, this week was whale shark day! And who am I to argue? I personally have not yet had the pleasure of encountering them in the wild, but they are definitely one of my very favorite marine organisms. Seeing one of these gentle giants in person would complete my life! While their image is well known, how much do you know about them as animals? Here are a few fun fast facts about whale sharks:

  1. Though they carry the name whale, they are true sharks. They get their name primarily from their size. Growing to an average size range of about 5.5 to 10m in length (18 – 32.8 ft) and an average of 20.6 tons, they are truly giants. Some have been measured upwards of 40ft in length! To put this into visual perspective, a full-grown adult whale shark is about as long as and heavier than the average American school bus! In fact, they are the largest species of not only shark, but of fish living today.

    WS Size
    Average size of whale sharks VS average size of humans! PC: Wikimedia/Matt Martyniuk
  2. They are filter feeders, not stereotypical predators. Like baleen whales and basking sharks, whale sharks eat the tiniest of marine organisms (and the occasional small fish who’s in the wrong place at the wrong time). They do so by filtering large volumes of water through their massive mouth. They are able to filter water in two ways 1) passively by swimming through clouds of plankton with their mouth open (known as ram feeding – they are literally ramming the water/plankton into their mouths) or 2) actively by sucking in plankton filled water from a stationary position (gulping in the traditional sense). In either case, they do actively seek out places with high concentrations of plankton so that they can get the most bang for their buck. Unlike baleen whales though, they do have teeth. They have upwards of 350 or more rows of teeth! Their teeth however are very small and are obviously not used in feeding.

    Whale shark eating plankton. PC: Jaontiveros & Togabi
  3. They can be found all over the world in warm, tropical waters. They are most frequently seen in Central and South America, South Asia, parts of Africa and in Australia (during the springtime spawning season of the Ningaloo Reef). Additionally, new research suggests that whale sharks also frequent the waters around Hawaii. Whether the islands of aloha act as a stop over or support their own resident population is yet unknown.

    WS Range
    The blue indicates the global range of whale sharks. PC: Cypron Map Series, The Emirr
  4. Their characteristic spots form a unique pattern that only that individual has – basically it’s their version of a fingerprint! And they don’t just have spots either. An accurate observation of whale shark skin will reveal that they have a combination of prominent white spots AND thin white stripes that divide the rows/columns of spots. Researchers use these unique patterns as their main means of identification of individual sharks. Identification studies are conducted for a variety of reasons, including learning average life spans, population counts, migration patterns/range, site fidelity, major congregating locations (feeding or breeding) and more.

    Whale shark spots
    Whale shark spot and stripe pattern. PC: Abe Khao Lak
  5. Their ‘best photo side’ is the left side. In recent years, researchers have collaborated to create a growing international photo data bank of whale sharks to try and identify as many as possible. But, in order to keep data collection consistent and prevent counting a shark twice, only photos of the left side of the shark are used. Specifically, the left side of the shark directly behind the fifth gill slit. This is because sharks’ skin patterns are not bilaterally symmetrical (mirror image from side to side) but are completely different and unique. To aid in the ID process, researchers use NASA software that IDs star patterns to analyze the patterns and compare it to already known individuals. Once the software narrows down the possibilities, a scientist must manually compare the photo to the suggestions and make the final call on whether it is an already known shark, or a newly photographed one.

    whale-shark-spot ID
    Red box indicates area used for pattern ID process.
  6. This is also a great area of research that uses citizen science – aka, anyone can get involved in it! Outside of the main congregation sites, finding whale sharks can be very difficult. Any recreational diver, snorkeler or fishermen who happens upon a whale shark and can get a clear photo of the left side can send their photo to organizations that collect and analyze these photos. For those lucky enough to encounter one in Hawaii, you can send your photo to the scientists at Hawaii Uncharted Research Collective. I had the pleasure of virtually meeting them earlier this year when they videoconferenced a teen group I help mentor and can personally attest to their amazingness! This small group of scientists dedicate their spare time to creating the first whale shark data base in Hawaii to better understand the animals that can be found there (and answer questions like the one I mentioned in #3 of this list!). Before they began their work, practically nothing was known about whale sharks in this part of the world. If you’re interested, I highly highly recommend visiting their site to learn more about their hard work and how you can get involved. HURC
  7. They are currently listed as endangered by the IUCN and studies indicate their populations are decreasing ☹ This decline is due to a variety of factors such as entanglement in fishing lines, boat collisions and though they are protected in most countries, like big game animals on land, they are subject to illegal poaching due to black market Eastern medicine trade. Ecotourism of whale shark sightseeing is on the rise however, with hope that this may spur more people towards conservation. A recent study found that one manta ray is worth over a million dollars throughout a lifetime worth of ecotourism! It is strongly suggested that whale sharks can be just as, if not more valuable. Like manta rays, they are extremely docile, extremely indifferent to the presence of people, are relatively slow movers, and are large, photogenic creatures. I know I’m not the only one who would pay lots of money to be near one! So hopefully their future becomes a bit brighter soon.

    PC: Marcel Ekkel


Well, hopefully this little list gives you a glimpse on why I love whale sharks so much, and maybe inspired you to learn more about their conservation! From their size, to their beautiful pattern coloration to their shared loved of the tropics, I think they are some of the coolest fish in the sea.

For guidance in whale shark encounter etiquette or to aid in their research, see HURC’s website at or review their user friendly PDFs :Encounter Guide Citizen Science

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