"So it takes a lot of them" to fill the belly of a blue whale, Mate says. He estimates that a blue whale might go through as much as three tons of krill in a single day.
Then it's off to the next area, where surface winds whip up the surf, causing an "upwelling" of nutrient-rich waters from far below the surface. The upwelling brings the nutrients up so that blue whales can crash through the krill, their mouths wide open, scooping up thousands of the small critters in a single pass.
The blues don't waste any time getting to the next upwelling, Mate says. He has seen them cruising along at about 20 miles an hour, or even faster if there's a pod of killer whales in the area.
The El Niño Diet
In recent years, he says, there has been a surprisingly large number of blues off the Santa Barbara Channel in Southern California, apparently because of the El Niño. Although we associate El Niño with a warming of the Pacific Ocean, its effect in some areas is quite different.
The numbers surged at the west end of the channel during the El Niño of 1992, and scientists think El Niño generated local winds that caused an increase in the upwelling, thus providing more food for the blues.
And during the strong El Niño of 1998, Mate says most of the blue whales he saw were "visibly emaciated," suggesting that shifting winds reduced the upwelling in many traditional feeding grounds, thus depriving the whales of the fat they need to get through the lean periods.
Mate's research has added a few more facts to the story of the blue whales, but he's the first to admit that there are huge gaps in our understanding of these magnificent beasts. Half the year, he says, nobody even knows where they are.
He plans to keep trying, he says, to fill those gaps.
"These animals are just awe inspiring," he says. "And if I ever stop being awestruck and inspired by them, I'll move on to another field."
Lee Dye’s column appears weekly on ABCNEWS.com. A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.