The biggest fish in the sea is also one of the least understood. The whale shark can be found roaming warm waters around the globe with its huge mouth agape in search of dinner. As it swims, it sucks in water. Food stays in while the water gets blown out the whale shark’s gills.
Though the largest existing shark, the whale shark is docile. The strange, spotted beast’s 300 rows of tiny teeth are almost useless. Ocean tourists sometimes enjoy diving in to swim with the creatures (though scientists discourage this; it may alter the giant fish’s natural behavior).
Last summer, for the purpose of gathering data, a group of scientists dedicated several weeks to diving with whale sharks in the Galapagos Islands. They tried some never-before-used techniques on the species. The whale shark is classified as “vulnerable” because of shrinking numbers but not yet “endangered.” Tests included taking blood samples and attempting ultrasound exams, all while swimming furiously alongside underwater.
Among other things, scientists are trying to conclude where the sharks feed and breed, whether they migrate and how far, and where and how they raise their young.
Here’s some of what they’ve learned:
The whale shark grows to between 20 and 52 feet long! It typically weighs more than 20 tons. That’s bigger than a double-decker bus!
Whale sharks are filter feeders, like whales. They eat only plankton, fish eggs, and very tiny fish and jellyfish.
Male and female whale sharks travel and feed separately. Scientists may find hundreds of mostly male sharks scooping up fish eggs together—with no clue where the females are feeding at the same time.
Only one pregnant whale shark has ever been found. That one, discovered off the coast of Taiwan in 1995, was deceased. Remarkably, it had 300 embryos inside—all at different stages of development.
Almost all of the whale sharks spotted in the waters around the Galapagos Islands are female, and many are thought to be pregnant. Scientists attached tracking devices to seven in their study, hoping to follow them all the way through to the birth of their expected offspring.
Conducting a medical exam on a free-swimming whale shark is difficult. The researcher team obtained only two blood samples. Ultrasound exams were inconclusive. Most ultrasound machines for animals are intended for abdominal walls that are one to two inches thick. But a whale shark’s abdominal wall is about eight inches. More powerful machines are needed to evaluate these examples of God’s gentle giants in the future.
