Whale sharks do the math to avoid that sinking feeling

November 25, 2010

They are the largest fish species in the ocean, but the majestic gliding motion of the whale shark is, scientists argue, an astonishing feat of mathematics and energy conservation. In new research published today in the British Ecological Society's journal Functional Ecology marine scientists reveal how these massive sharks use geometry to enhance their natural negative buoyancy and stay afloat.

For most animals movement is crucial for survival, both for finding food and for evading predators. However, movement costs substantial amounts of energy and while this is true of land based animals it is even more complex for birds and which travel in three dimensions. Unsurprisingly this has a profound impact on their movement patterns.

"The key factor for animal movement is travel speed, which governs how much energy an animal uses, the distance it will travel and how often resources are encountered," said lead author Adrian Gleiss from Swansea University. "However, oceanic animals not only have to consider their travel speed, but also how vertical movement will affect their , which changes the whole perspective."

For the past four years, Adrian Gleiss and Rory Wilson, from Swansea University, worked with Brad Norman from ECOcean Inc. to lead an international team to investigate the movements of whale sharks, Rhincodon typus, at Ningaloo Reef in Western Australia. They attached animal-borne , accelerometers, to the free-swimming whale sharks to measure their swimming activity and vertical movement, which allowed them to quantify the energetic cost of vertical movement.

The team's data revealed that whale sharks are able to glide without investing energy into movement when descending, but they had to beat their tails when they ascended. This occurs because sharks, unlike many fish, have negative buoyancy.

Also, the steeper the sharks ascended, the harder they had to beat their tail and the more energy they had to invest. The Whale Sharks displayed two broad movement modes, one consisting of shallow ascent angles, which minimize the energetic cost of moving in the horizontal while a second characteristic of steeper ascent angles, optimized the energetic cost of vertical movement.

"These results demonstrate how geometry plays a crucial role in movement strategies for animals moving in 3-dimensions," concluded Gleiss. "This use of negative buoyancy may play a large part in oceanic being able to locate and travel between scarce and unpredictable food sources efficiently."

Explore further: Photo-monitoring whale sharks

More information: Moved by that sinking feeling: variable diving geometry underlies movement strategies in whale sharks, DOI: 10.1111/j.1365-2435.2010.01801.x

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5 / 5 (7) Nov 25, 2010
The picture is not a Whale Shark, it is a Great White shark. Big, big difference.
3 / 5 (2) Nov 25, 2010
Sharks is sharks thinks the author.
5 / 5 (3) Nov 25, 2010
This isn't news. Sharks have been relatively unchanged for how many millions of years? Of course natural selection would have optimized their energy expenditure long before we have the means to study it. Moreover it's not like the sharks are working the angle:energy cost ratios as they swim along. This should have been titled "Scientists waste four years confirming sharks swim efficiently"
3.7 / 5 (3) Nov 25, 2010
Study confirms: theres still stupidity among the human race,.
2.5 / 5 (2) Nov 25, 2010
whale sharks, who knew!
3 / 5 (2) Nov 25, 2010
So, a trivial university department landed on a few data-loggers meant for attaching to marine vertebrates.

Some professor thought it would be nice to have some student do his thesis on what you can find slapping these loggers on some of the more readily available large "fish", in that particular area.

Result: a passable Master's Thesis, showing meticulous and diligent "science". (But not necessarily skill, talent, passion, or True Insight.)

I'm not particularly impressed by PhysOrg including this article on their web site. The same insights could have been made by any scientifically or physically astute citizen, merely lying in the rocking chair on their porch, simply observing the collection of readily visible avians.

I'd so like PhysOrg to earn the kind of respect and reputation that Scientific American has enjoyed for the last 150+ years. My Granddad already subscribed, and I have read some seriously old issues.

You really need to know what TO NOT PUBLISH.

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