Published: June 1991

Animal Navigation

Monarchs

Secrets of Animal Navigation

By Michael E. Long
Photograph by James L. Amos

This article was originally published in the June 1991 National Geographic.

Up to my hips in the dark swirling waters of Idaho’s Salmon River this frigid November morning, encased in thick neoprene waders and pelted by an insistent rain, I feel like a fisherman disguised as a snow tire. I am casting flies to entice a silver bullet of a fish, between two and three feet long, called a steelhead because its forehead is gunmetal blue. Though its brain is about the size of a peanut, this Pacific salmon is completing an epic round-trip voyage of several thousand miles entailing wondrous feats of navigation.

Three years ago myriads of yearling steelhead home to spawn. From widely scattered locations they head for the American coast, joining steelhead from Oregon's Deschutes and other rivers in running a gantlet of drift nets, killer whales, sea lions, and seals.

Entering the Columbia River estuary, the fish must escape humans with rods and gill nets and traverse fish ladders—a series of water-filled concrete stairs—at Bonneville and seven other huge hydroelectric dams. Ignoring the mouths of the Deschutes and a score of other tributaries, the Salmon River steelhead enter the Snake and turn left into the Salmon, fighting their way up the raging torrents to the place of their youth.

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