Cracking the mysteries of the elusive, majestic whale shark
Cracking the mysteries of the elusive, majestic whale shark In this 2017 photo provided by Simon Pierce, Jonathan Green checks on a fin-mounted satellite tag on a whale shark in the Galapagos Islands area of Ecuador. ( via AP)
Cracking the mysteries of the elusive, majestic whale shark
Lexile: 880L

Assign to Google Classroom

It's the biggest shark. And it is the biggest fish in the sea. It is often found roaming in warm waters around the globe. It often has its huge mouth agape in search of dinner.

Yet despite its hulking appearance, the whale shark has only tiny, almost useless teeth. It is sometimes so docile that entire boatloads of people can swim alongside the enigmatic, spotted beast. It's also one of the least understood animals in the oceans.

A group of scientists spent several weeks diving with whale sharks in the Galapagos Islands. This was last summer and fall. They were attempting to solve some of the most enduring mysteries. They tried some never-before-used techniques on the species in the wild. For instance, they took blood samples and did ultrasound exams. They did this while swimming furiously beside them underwater.

Here's what's known about these massive marine animals. And here is what scientists are still trying to find out:


While they are comparable in size to whales, whale sharks are sharks. They typically grow to be bigger than a double-decker bus. They grow to 20 to 52 feet. They can weigh more than 20 tons. But they are filter feeders. As such, the enormous whale sharks are dangerous only to the plankton, fish eggs and tiny fish they chomp on.

The gentle giants aren't particularly fast when compared to other sharks. But a simple wave of their tail propels them through the water faster than any human could ever swim. They have broad, flat heads. Their entire dark-blue bodies are covered in dots that act as camouflage underwater.

They have been overhunted by fishermen for years. Now whale sharks are endangered and at risk of extinction.


Whale sharks prefer warm waters. They are often found feeding at locations around the world. These locations include Australia and the Philippines. It includes Mexico and even in the oil fields off the coast of Qatar.

Hundreds of whale sharks — mostly young males — gather in these areas at certain times of the year. They do this to scoop up fish eggs. It is unknown where adult females are feeding then.

The vastness of the ocean usually makes the shy animals hard to find. Jacques Cousteau only ever saw two in his decades of sea exploration.


Marine biologists have been tagging whale sharks in recent years. They do this to track their movements. Others are trying to answer questions about their life and reproductive cycles. Only one pregnant whale shark has ever been found. In 1995, a dead whale shark was found off the coast of Taiwan with 300 embryos inside. All the embryos were different stages of development.

"The million-dollar questions are where are they mating, hunting and where do their young live?" That's the question asked by Jonathan Green. He is director of the Galapagos Whale Shark Project.

An international database was launched to identify as many whale sharks as possible through their distinctive dot pattern. Each shark has a unique configuration of dots. The dots act like a fingerprint. More than 8,000 sharks have been logged so far. Scientists can only afford to spend a few weeks in the Galapagos each year. So they depend on photos taken by visiting divers to figure out what the whale sharks are up to. So far, none of the sharks spotted in the Galapagos has been seen anywhere else.


It is difficult to conduct a medical exam on a free-swimming whale shark. So researchers only obtained two blood samples. These samples haven't yet been tested. The ultrasound exams were inconclusive. That's because more powerful machines are needed. Most ultrasound machines for animals are intended for abdominal walls that are 1 to 2 inches thick. But a whale shark's abdominal wall is about 8 inches.

"When we first started studying these large animals, nobody knew how to go about it," Green said. "Now that we have better technology and more experience, we will hopefully be able to answer some of the fundamental questions soon."

Besides blood and ultrasound tests, scientists successfully tagged seven sharks. While not a large number, it's important since so few whale sharks are tracked. The pressure of deep water can cause tags to drop off if the sharks dive below 2,000 meters. The animals often do if they're traveling long distances or possibly giving birth. But any migratory data the scientists collect when sharks stay at shallower depths can help build a picture of the sharks' life cycle.

Green and colleagues are planning further expeditions to the Galapagos later this year to continue their research. They plan to gather more blood samples and continue satellite tagging.

"When you have so few data points, every single shark is important," said Robert Hueter. He is the director of the Center for Shark Research at Mote Marine Laboratory in Florida. He was not part of the Galapagos research. "These aren't like goldfish where you can get sample sizes of hundreds at a time."


In the last 75 years, the vast majority of whale sharks have been hunted by people for food and their numbers are still dropping, said Simon Pierce. He is chief scientist at the Marine Megafauna Foundation.

Some biologists worry climate change could hurt the sharks by reducing their food supply. Rising ocean temperatures could mean less plankton.

"If we do the things that are necessary to conserve the whale sharks, we'll be conserving the ocean itself," said Simon Thorrold. He works at the Woods Hole Oceanographic Institute in Massachusetts.

For Green, who heads the Galapagos project, it's more personal. "Even after years of diving with whale sharks, I still get goose bumps every time I see that huge blue shadow in the water. It's an incredibly emotional experience."

Source URL:

Filed Under:  
Assigned 525 times
How can a shark be a whale?
Write your answers in the comments section below

  • calliy-orv
    3/12/2018 - 02:04 p.m.

    i never heard of these before. i wonder if they are rare or going extincted.

  • kinniel-orv
    3/12/2018 - 02:36 p.m.

    The whale shark is a active feeder, targeting concentrations of plankton or fish.

  • brycew-orv
    3/12/2018 - 07:21 p.m.

    Idk same reason we have a spider monkey who knows

  • Charlotte-E2
    3/13/2018 - 11:57 a.m.

    I think that it is cool that they are studying whale sharks. i also like that they are trying to figure out if it is a WHALE or SHARK? I think that a lot of people are wondering if a whale shark is a whale or shark.

  • ethanm-orv
    3/13/2018 - 12:13 p.m.

    they don't say what the mysteries are though

  • Cynthiat-orv
    3/13/2018 - 02:39 p.m.

    If I was an animal that lived I the ocean I would choose to be a whale shark.

  • MichaylaG-smi
    3/14/2018 - 05:40 p.m.

    I learned that whale sharks are actually sharks and not whales. They also cant's harm humans.

  • TimT-dec
    3/15/2018 - 01:33 p.m.

    The shark is actully not a whale. It just resembles more a whale then a shark.

  • MakaylaP-dec
    3/15/2018 - 01:40 p.m.

    A shark can be a whale if they are large/huge enough and are heavy enough.

  • JacobS-dec1
    3/15/2018 - 01:52 p.m.

    It is a type of breed.

Take the Quiz Leave a comment