Whale sharks do it deeper

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A close encounter with a whale shark is one of the “things to do” on the life list for many scuba divers and snorkelers. Perhaps you have been one of the lucky few to swim with these enormous friendly elasmobranchs off Honduras in Utila (pictured), off Belize at Gladden Spit, or off the coast of south Texas in Flower Garden Banks National Marine Sanctuary. My encounters with whale sharks are limited to breathless descriptions from fellow divers. I left the water too soon, or arrived a day late. I watched the video hoping it will happen some day soon.


Rachel Graham and Dan Castellanos of the Wildlife Conservation Society in Belize have been tagging whale sharks and manta rays for several years. Rachel published a 2005 study in the Royal Society with co-authors Callum Roberts and James Smart at the University of York. The study documented the diving behavior of four whale sharks tagged during an annual snapper spawning event under a full moon.

The results demonstrated that a free-ranging whale shark displays ultradian, diel and circa-lunar rhythmicity of diving behaviour. Whale sharks dive to over 979.5 m, making primarily diurnal deep dives and remaining in relatively shallow waters at night.

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Reference:

Graham, RT, Roberts, CM, Smart, JCR. 2005. Diving behaviour of whale sharks in relation to a predictable food pulse. The Royal Society.

Peter Etnoyer (406 Posts)

PhD candidate at Texas A&M University- Corpus Christi and doctoral fellow Harte Research Institute for Gulf of Mexico Studies.





3 comments on “Whale sharks do it deeper
  1. Fascinating piece Peter, I had no idea whale sharks were found off the coast of Texas!

    I am continuously amazed at all the deep-diving megavertebrates we’ve been highlighting this week. Its interesting how so many of the deep-diving behaviours correlate to diel-vertical migratory patterns into the midwater domain. This is one of the least studied areas on the planet. I think this week’s post highlight how important this domain is to large vertebrates and merits much more funding to study midwater eology!

  2. I recently visited the Georgia Aquarium and saw the whale sharks on display there. Even those subadults are awe-inspiring, although it made me feel sad as well, there really is no captive environment that can even get close to allowing a simulation of their behavior (diving depth, etc) in the wild. It can be argued how much “pleasure” whales get from diving deep, fast, etc, but it still seems to me like captive ones would pick up on the fact that they’re missing SOMETHING…

  3. It would be interesting to know if subadult diving behavior differed from adult diving behavior. We’ll have to ask Rachel about that. Perhaps the young have yet to discover what lies below. Regardless, the only thing that doesn’t make me sad about a captive whale shark is knowing they are safe from (human) predation. I hear they are hunted in the Philippines.

    You are right, Kevin, that mid water ecology and deep diving behavior both warrant further study and better financial support. I’ll address this tomorrow with a parting shot and farewell to Megavertebrate Week.

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