Wednesday, April 21, 2010

Open mike at a night dive!

It is amazing how the underwater world can continuously surprise you! Sometimes it is not so much about the dive site, but about the dive itself. Recently, we had a father and son buddy team from the US, John and Taylor Wilcox, join us for a night dive. Oswaldo decided that the night looked perfect do to a dive at The Cathedral (west end of Jost van Dyke). Joined by one of our intern instructors, August, the adventurous group of four headed to the depths in a starry night to see what their torches could find. Well, the highlight of the dive was not so much what they found, but the musical accompaniment they had. As described by one of the divers: “I just closed my eyes and sat there feeling the vibrations and hearing the whales sing”. It turns out that they were hearing the musical cadence of a nearby pod of humpback whales. Water is an excellent conductor of sound vibrations, therefore, making sound travel about four times faster underwater than at the surface. So our divers “felt” in addition, to simply “hear”, the ongoing sounds produced by the humpback whales. How they knew there were humpback whales? Because it is toward the end of the migration season, and this area is part of the grounds they cover to come and go between their breeding and feeding grounds. According to what I have read about humpback whales and information found in the internet, only male humpback whales are known to sing and their song have been acclaimed by many scientists to be one of the most complex in the animal kingdom. It is part of the sexual selection process, and also they have been instances were the songs were identified as being used for territorial designation or feeding calls. Since they do not have vocal chords, the exact mechanism that produces the sounds that result in the whale songs, is unknown. The most recent studies point to the fact that since whales have an outstanding lung capacity, these songs are produced by moving the air internally, through the larynx and the cranial sinuses.
Night dives usually showcase the secret of the marine underworld, giving us a chance to see what’s hiding during the day: the bright colored polyps on the corals are opened, basket stars extend to feed from the passing current, octopi and eels roam the reef looking for food, and much more. On this dive our divers were treated with a unique sensory experience that went beyond their expectations. Lesson learned: never pass on a night dive again; you don’t know what you will miss!
Note: The humpback whale picture was not taken during the dive. We really (really, really) wish that we would have had the amazing luck to take it, but no. We borrowed it from the internet.

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