Published: November 2010

Great Migrations

Great Plains Bison

Animal Migrations

What is it that makes animal migration such a magnificent spectacle for the eye and the mind? Is it the sheer abundance of wildlife in motion? Is it the steep odds to be overcome? Is it the amazing feats of precise navigation? The answer is all of the above. But there’s another reason why the long-distance journeys of wildebeests, sandhill cranes, monarch butterflies, sea turtles, and so many other species inspire our awe. One biologist has noted the “undistractibility” of migrating animals. A nonscientist, risking anthropomorphism, might say: Yes, they have a sense of larger purpose.

By David Quammen
Photograph by Joel Sartore

Animal migration is a phenomenon far grander and more patterned than animal movement. It represents collective travel with long-deferred rewards. It suggests premeditation and epic willfulness, codified as inherited instinct. A biologist named Hugh Dingle, striving to understand the essence, has identified five characteristics that apply, in varying degrees and combinations, to all migrations. They are prolonged movements that carry animals outside familiar habitats; they tend to be linear, not zigzaggy; they involve special behaviors of preparation (such as overfeeding) and arrival; they demand special allocations of energy. And one more: Migrating animals maintain a fervid attentiveness to the greater mission, which keeps them undistracted by temptations and undeterred by challenges that would turn other animals aside.

An arctic tern on its way from Tierra del Fuego to Alaska, for instance, will ignore a nice smelly herring offered from a bird-watcher's boat in Monterey Bay. Local gulls will dive voraciously for such handouts, while the tern flies on. Why? "Animal migrants do not respond to sensory inputs from resources that would readily elicit responses in other circumstances," is the dry, careful way Dingle describes it. In plainer words: These critters are hell-for-leather, flat-out just gonna get there. Another way, less scientific, would be to say that the arctic tern resists distraction because it is driven at that moment by an instinctive sense of something we humans find admirable: larger purpose.

Continue »
email a friend iconprinter friendly icon   |