I‘ve posted videos before on the “barrel roll” of blue whales feeding on krill and on preliminary data collected by the workers mentioned below; but now there’s finally a published paper and stunning new video that documents how the world’s largest animal feeds on some of the world’s smallest (krill are tiny shrimplike crustaceans). Let me reprise the behavior first; it’s shown at the first part of this not-so-good video. The whale rolls over, opens its mouth, and engulfs a patch of krill.
Jeremy Goldbogen, a graduate student at the University of British Columbia, works on feeding in blue whales. In the video below, and the paper referenced below, he and his colleagues attached cameras to the backs of blue whales (Balaenoptera musculus, supposedly the largest creature that ever lived at 200 tons—the weight equivalent of about 150 Volkswagen Beetles), and followed their feeding behavior. The video, presented on National Public Radio’s Science Friday, is stunning:
In the paper, published in Biology Letters (free download here), Goldbogen and colleagues describe how (with the help of simulations), the 360° barrel rolls that the whales do when nomming serve two purposes: to orient the whales so they can get a good look at the prey patch from all angles (their eyes are, of course, on the side), and to enable them “to engulf the densest portion of the prey patch.” I’m not sure how the inversion does this, but the video at top suggests that the upside-down position enables them to “scoop up” the water more effectively.
According to Goldbogen et al., a single judiciously executed barrel roll by a dense patch of krill can provide the whale with enough food for an entire day!
The authors also mention three other cases of animals doing rolling maneuvers. I was familiar with the “death” roll of the alligator, in which the reptile spins around and around in the water with prey in its mouth, probably breaking its neck, ripping off a limb, or battering it to death.
Here’s a video of a crocodile doing the death roll, automatically, after it grabs a trainer’s arm [WARNING: don’t watch if you don’t want to see a human get bitten and his arm mangled]. I’m using the video because it shows the behavior so clearly, and how automatic it is.
The two other cases quoted by Goldbogen et al. involve “remora removal in spinner dolphins and “air-righting in geckos.” Here’s “air-righting” in geckos, but how could they forget that cats do it, too!?
The video below shows the dolphins spinning as they jump out of the water; one appears to go around three or four times! I’m not sure whether this is for removing the annoying remoras, but it’s new to me: