Until now we have only had our imagination and some fleeting video to judge what Whales do when they dive.
A surfacing whale is a sight to see, but it would be even more dramatic to watch one ply the ocean depths. Researchers have taken a step closer to doing just that with sophisticated radio-tagging technology and a new computer program that uses the data to recreate a whale’s path underwater. The results, presented here yesterday at the annual meeting of the Society for Integrative and Comparative Biology, are helping scientists understand how the school bus-sized beasts are able to take in enough food to sustain their great girth, and how underwater noises, such as sonar, might affect their well-being.
Comparative physiologist Jeremy Goldbogen of the Cascadia Research Collective in Olympia, Washington, studies feeding in blue fin and other so-called rorqual whales. For almost a decade, he and his colleagues have been attaching suction cup radio tags onto the backs of the cetaceans. The tags record depth, sound, and other parameters as the whales swim. After a set amount of time, they fall off, float to the surface, and send out a radio signal so they can be retrieved and their data analyzed.
The work showed that in one giant gulp, a blue whaleâ€”the biggest creature on Earthâ€”takes in 125% of its body weight in water and krill. During their dives, the cetaceans ram into patches of krill, opening their mouths wide and wrapping their jaws around prey-laden water, a move that stops them short. Next, they close their mouths and push water through their baleen, a system of plates that filter out the food, then speed up for another feeding bout.
There is a cool video that shows about 20 minutes of diving and feeding behaviour (compressed into a 30 second video):
…a tagged blue whale dives twice over the course of 19 minutes. The movie shows the whale moving at about 50 times its cruising speed. The first dive, to about 15 meters, takes about 2.5 minutes in real life; the second one, which includes feeding bouts, lasts more than 12 minutes and reaches down to 180 meters, where the whale lunges five times in quick succession, as if it were on a roller coaster.