Whale Sharks Move in Mysterious Ways: Watch Them Swim

The gentle giants take surprising "road trips" to faraway destinations, scientists discover.

Move over Mary Lee, there may be new celebrity sharks in town. That's because scientists with Conservation International have placed tracking devices on whale sharks in Indonesia and have set up near-real-time monitoring of the movements of the giant fish. Already, the devices are revealing surprising mysteries about the gentle giants, leaving scientists scratching their heads.

The new online map has an undisclosed lag time in order to deter poaching of the huge sharks, which are the largest fish in the sea.

Last year, Conservation International scientists attached fin-mounted cameras to 16 whale sharks in Cendrawasih Bay, in eastern Indonesia's Birds Head region.

Because the animals are so large and hard to catch, the scientists partnered with local fishermen. When one of the sharks was accidentally caught in a net, the team would be called in to place a tracker and then release the animal.

Scientists had thought this group of whale sharks hung out mostly in the bay, where they are often seen by divers. That turned out to be only partially correct.

While the sharks do spend most of their time in Cendrawasih Bay, they were also observed swimming up to  1,300 kilometres away, to the Philippines, Papua New Guinea, and Palau. These long voyages were often short "road trips," with the animals repeatedly returning to Bird's Head.

The reasons for the trips are unclear. They may be related to mating, although the road trippers were juvenile males that were not yet ready to breed, the scientists note. (See why the world's biggest whale sharks are disappearing.) It's also not known if the trips are culinary adventures, since the year-round abundance of silverside baitfish in the bay seems to provide a steady food source, notes Mark Erdmann, the marine scientist with Conservation International who leads the tagging project.

One of the sharks was also recorded diving down to 1,808 meters (nearly 6,000 feet), more than twice the height of the world's tallest building. Again, the reasons are unclear.

Further, 97 percent of the whale sharks identified in Cendrawasih Bay were young males. Where the females or older sharks are remains a mystery.

Erdmann adds that whale sharks play important roles in their ecosystem. They filter baitfish and small organisms out of the water. The huge, gentle sharks are also major draws for divers, often forming the basis of ecotourism operations. 

Whale sharks can reach lengths of 15 metres, with an average weight of 20.6 tons.

Better understanding where the sharks go, and why, can help conservationists better design marine protected areas and deter poaching, says Erdmann.

"It’s a reminder of just how little we know, even today, about life in the sea," he writes in an email.

WATCH: See what a whale sharks sees.


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