The Largest Beast’s Long Migration

Blue whales shock us with their size. But their efficiency and endurance are greater still. /

So God created the great creatures of the sea and every living thing with which the water teems and that moves about in it. . . . And God saw that it was good (Gen. 1:21).

Moving fast in water burns your energy budget at ruinous rates, but another challenge presented by the wide ocean is the possibility of long-distance migrations. From some parts of Antarctica, a gaze due north runs across open ocean all the way to the Arctic Circle. Such broad swaths of habitat are opportunities for very long distance travel—and some ocean species use them. Powering those migrations demands different solutions than the solutions for speed.

Thirty feet deep in the open ocean, the blue varies from transparent to a dusky dark that seems to swallow light. Waves march above in a long repeating line, striving for the nearest shore, thousands of miles away. A silence lies throughout the sea like unbroken fog.

Unexpectedly, a shape slips past, giant and dark, with a powerful flat tail and two wide fins splayed out to either side. A second, smaller shape ghosts behind. They rise to the surface synchronously, blow several fishy-smelling notes in quick succession, and sink back to their placid hike.

When they are gone, the ocean returns to empty waiting.

Some of the longest migrations on our planet are by swimmers. Blue whales slip from the Southern Ocean near Antarctica to subequatorial seas. Humpbacks announce their annual return to Hawaii, after a long swim from Alaska, with shows of exuberance above the water and majestic operas beneath. Gray whales leave their foraging grounds in the Bering Sea and meander down the coast of California to breeding lagoons in Baja Mexico.

For humans, swimming is wonderful exercise, because water is heavy. Moderate-speed swimming burns as many calories as fast running, rowing, or cycling. As any parent of a competitive swimmer can attest, it takes tremendous food energy to swim. Olympic swimmers may consume upward of 10,000 calories per day. Given these huge costs, how and why do whales manage such long migrations?

Whales tank up before a long swim. Often their feeding areas are in far polar seas, and they spend their summers feasting on the bonanza of food that a short, intense polar summer can produce. But as winter approaches, the water gets colder, and the plankton fade into a fallow offseason. So the feeding grounds are abandoned, and migratory whales turn for the tropics at summer’s close.

With full bellies, they still face 5,000 miles of cold water between their food supplies and winter havens. They aren’t explosive athletes; if a dolphin is a supercharged cherry red motorcycle, these migratory titans are freight trains rumbling from coast to coast. Like those trains, they take a while to get up to speed. Acceleration isn’t nearly as valuable as efficiency, so the giants propel themselves with powerful deliberate strokes. A blue whale routinely cruises at about 1–4 miles per hour, wasting not a scrap of strength or movement. Once a great whale reaches cruising speed, it doesn’t take much energy to maintain that speed.

Their size draws the most attention, but migratory whales are marvels of engineering. A blue whale (Baloenoptera inusculus) is the greatest example, stretching 200 tons of mass out to a surprisingly slender 100-foot length. The tail fluke delivers thrust at 90 percent efficiency—far higher than the best commercial ship propellers, which churn and grasp desperately for thrust that the whale fluke seems to calmly command. Backing up these traits is a steely endurance, pushing the traveler across entire oceans in just weeks, without feeding.

They arrive on wintering grounds, rest, nurse their young, and sing the melancholy songs that attract mates (whales are big into Morrissey). They choose warmer water, gamboling across the reefs of Tonga, frolicking in Baja’s lagoons. Shivering less than they did in the cold polar seas, the energy saved by summering in warm water can recoup migration’s costs. New calves likely benefit most from the heat; being small, they lose more heat per unit of body mass than their parents do. They also avoid their fiercest predator: Orcas hunt in colder waters and feed on helpless yearling whales when they can. Warm winter waters are a haven against some of these dangers.

The end of winter is a hungry time for a migrating whale—especially a mother who has nursed her young calf, drawing on the food reserves she laid down the summer before. Yet the reverse migration lies ahead for these animals, thousands more miles, this time on an empty stomach. Food at the end of this journey looms as a critical need for even the biggest animals on Earth, and they arrive ravenous in the polar summer seas.

Lately, that food has been harder to find for some whales. In 1999, a large fraction of gray whales (Eschrichtius robustus) were observed to be thin, even emaciated. The death rate of calves on migration was huge, and hundreds died. The reason has been traced to the northerly retreat of their food supply: instead of the wide field of tasty crustaceans that gray whales normally find in the Bering Strait, the whales found nothing. Their food supply had responded to warming waters and had retreated to the north. The grays weren’t helpless—they followed the trail and found meals at last, at the cost of hundreds more miles and countless calories. Some whales probably didn’t find enough food fast enough, and their calves died. Others plowed north into the Chukchi and Beaufort Seas, victims of a warming ocean, looking for food.

Gray whales are regularly seen much farther to the north than they used to be. But one animal stunned the whale-watching world in 2010 by turning up off the coast of Israel in the Mediterranean Sea. No gray whale had ever been seen in the Mediterranean, and the species was hunted out of the Atlantic around the year 1700. For 300 years, this species has been restricted to the Pacific. This one whale may have slipped through the Bering Strait and across the Canadian Arctic ice fields, swimming thousands of extra miles, pushing the normal migration distance far, far longer. Once the wanderer emerged in the North Atlantic with a full belly, it simply followed instinct: head south for the winter and eventually turn east into a nice warm lagoon. This lagoon happened to be the Mediterranean, not a breeding site in Baja.

However it managed the journey, this whale disappeared and has not been seen in either ocean since.

Excerpted from The Extreme Life of the Sea by Stephen R. Palumbi and Anthony R. Palumbi. Copyright © 2014 by Princeton University Press. Reprinted by permission. Scripture epigraph added by The Behemoth’s editors.

Follow The Behemoth on Twitter and Facebook.

Also in this Issue

Issue 21 / April 30, 2015
  1. Editors’ Note

    Issue 21: Redeeming the Law, whale migration, cell sacrifice, and farsightedness.

  2. I Fought the Law

    Now I think it’s time to rehabilitate its unsavory reputation. /

  3. Greater Love Has No Cell

    The biblical allegory written into our bodies. /

  4. Presbyopia

    ‘By some miracle, she felt a lifting / lost the tyranny and weight of near things’ /

  5. Wonder on the Web

    Links to amazing stuff /

Issue Archives