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