Brian Keating swims alongside La Paz's mysterious whale sharks

Alberta naturalist Brian Keatinggotup close and personal this week with some of the largest and most mysterious underwater creatures in the Baja Peninsula.

The wildlife columnist for CBC's The Homestretch and Radio Activespent the past week swimming alongside whale sharksin the Sea of Cortez at La Paz, Mexico.

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Weighing in at roughly 20 tonnes, whalesharks arethe largest non-cetacean living creatures on the planet.

"When you're swimming with them, it's like swimming with aWinnebago. They're such huge animals," said Keating, who saw his first whale shark less than 15 minutes out of the bay.

By the day's end, Keating had metat least a dozen whale sharks. He evenmanaged to snapa few underwater photos from their tail end as proof.

Filter feeders

Whale sharks are a one of just three species of sharkfilterfeeders, Keating said.

The animals, which have mouths that can be up to a metre and a half wide, eatby swimming with theirmouths wide open andforcing food in, orby gulping inwater at the surface.

"We floated hardly a meter from the whale shark's head, giving us an incredible opportunity to see how she sucked in sea water, sometimes creating a vortex of downward spiralling bubbles," Keating said.

"We could actually see some remora fish inside the mouth, which are suction cup fish, hanging on for the ride. It was an extremely remarkable experience."

Mysterious animals

"The thing about the whaleshark that is so remarkable is that nobody really knows where they breed, or how they breed, or where they give birth," Keating said.

The 1995 capture and study of a femalewhale sharkthat was pregnant with 304embryoshas led scientists to believe that whale sharks actuallystore sperm from one mating and produce their young over a period of time.

This allows them to givebirth tolive young, known as pups, at different locations and times.

"There's lots of mysteries about these animals," said Keating, who noted that smallwhalesharksare hardly ever seen.

"The good news about whalesharks is that there's now pretty well entirely an international ban on killing these," he said.

"The flesh apparently is not very good to eat anyway. It tastes apparently like tofu."

You can follow Keating's adventures online on Twitter and Facebook.