What do you do if you're the largest animal on the planet, tipping the scales at around 100 tons? You worry, a lot, about where you're going to find your next meal.
New research out of Oregon State University shows that the mighty blue whale, because of its immense size, has to feed almost constantly just to stay alive. That's quite different from other whales, like the grays and the humpbacks, that can go for months without food.
As soon as the blue whale has finished slurping up krill at one nutrient-rich area, it races off in search of another meal, because it can't afford to lose any time in its battle for survival.
That desperate search for the maritime equivalent of fast food joints is just one of the findings from an ambitious, multi-year study of the blue whale conducted by Bruce Mate, director of the Marine Mammal Program at OSU.
The findings add a little more to our understanding of a magnificent beast that has just barely survived the fierce appetite of its hungriest predators — humans. The blue whale, which can reach lengths of 100 feet, was nearly hunted to extinction before it received international protection.
It's numbers have dropped from about 186,000 prior to human exploitation, to an estimated 7,000 to 8,000 "true blues" worldwide today.
And it's not out of trouble yet.
"People sometimes tell me they want to come back in the next life as a whale," Mate says. "I tell them they better be prepared to work hard."
For the blue whale, Mate says, the search for food never ends, and there's always the threat of killer whales which have been known to attack a blue whale, many times their size, and bite off chunks of flesh until the whale dies.
Mate has been a lot closer to blue whales than most experts, because his research required him to inject a small dart, about the size of a human finger, into the side of blue whales while they were gorging on krill. He had to guide his boat to within about 10 to 15 feet to dart the animals, and he says the process didn't even interrupt their meals.
"They don't even seem to be aware of it," he says.
In all, Mate has tagged 100 blue whales, mostly off the coast of California. Each tag contains a tiny transmitter which sends data back to Mate via the Argos satellite system. What came out of all that was a treasure chest of data on animals that we really know very little about. Some of the tags transmitted data for four or five months before their batteries died, giving information about travel speed, location, and feeding habits.
"We tracked one blue whale for 307 days before the batteries were exhausted," Mate says. "That provides a lot of data."
The data shows that blues live a very different lifestyle from other whales.
"Unlike gray whales, where the whole population does basically the same thing in a four to six week period of migrating south (to their mating area) the blue whales are much more individualistic in their decisions about where they go and when they do what," he says.
For example, two blue whales tagged while feeding off Southern California remained in the same area for two weeks, and then both took off in nearly opposite directions. Gray whales hang together, and they go without eating for months at a time when heading south to mate, and then while swimming to their feeding grounds in the North Pacific.
Blues dine almost exclusively on krill, small crustaceans that are only about an inch-and-a-half long.
"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.