This particular bubble blast seemed to be commentary directed at our persistent and irritating little boat—some kind of whale expletive, probably. It rose above the whale's head like a speech balloon in a Gary Larson cartoon. Its message was something like "@*#&%√!?!"

Of all the marks of blue whale cursive, the most colorful was the defecation trail. The first defecation we saw was in a yearling, a little 50-footer. This whale blew 40 yards away, and behind it the ocean brightened in a long, red-orange contrail. "We have a defecation," Irvine announced. This contrail, a brick red streak of processed krill, more watery than particulate, was our first direct evidence that blue whales were feeding in winter at the Costa Rica Dome. As this was one of the hypotheses this expedition had been launched to test, Mate scrambled to find a Ziploc bag to collect a sample.

The evidence for feeding that we observed firsthand in the defecation trails was corroborated in the ship's laboratory. On her computer screen, Robyn Matteson, Mate's graduate student, monitored the echo sounder and the concentrations of krill it detected at the dome. Krill distribution was patchier than anyone had imagined, but dense schools of the small crustaceans were plainly here. Across the lab table, at their own computers, Calambokidis and Erin Oleson of Scripps Institution of Oceanography studied the dive profiles recorded by acoustic tags they had succeeded in applying to several whales. The acoustic tags, deployed by pole and attached by suction cups, stay on the whale for hours, not months, like the more invasive satellite tags. Here at the dome, the depth recorders on the tags showed dives to 800 feet and deeper. The vertical line marking each dive, on reaching its greatest depth, began to zigzag in the sawtooth pattern characteristic of blue whales when lunge feeding on krill.

The evidence for calving at the Costa Rica Dome proved more elusive, but after many fruitless days, it arrived finally, to starboard, by way of a mother and her calf.

The pair were moving slowly, spending a lot of time at the surface. The mother surprised us by allowing her calf to turn toward Pacific Storm. A mother whale often interposes herself between her calf and potential danger, but this mother was an easygoing, Montessori sort of parent, and she let her baby explore.

John Calambokidis drove Squall out to snap surface pictures for photo identification. Nicklin and cameraman Ernie Kovacs grabbed their gear and went along. On nearing the whales, they pulled on their fins and slipped overboard. At first they saw nothing through their dive masks but blue. Then Kovacs, looking for the youngster, was startled to see it pass, maybe five feet below his fins. This whale was just a baby, yet its blue back seemed to pass under him endlessly. The calf, gliding by Nicklin, rolled slightly to bring an eye to bear on him. It peered into the glass orb of the camera housing, and Nicklin's shutter winked back.