Traveling by Innate GPS-like Signals

Dr. Nathan Putman
Dr. Nathan Putman

From the April 2014 Desktop News | One of the most captivating mysteries in biology is the long-distance migrations of animals, particularly young animals that travel more than thousands of kilometers to specific, uncharted locations without older, more experienced migrants to guide them along the way.

A College of Arts and Sciences alumnus is changing the way scientists understand one such phenomenon – the migration of Pacific salmon.

Dr. Nathan Putman, a 2006 graduate of the Department of Biological Sciences and a current post-doctoral researcher at Oregon State University, published a study Feb. 6 in Current Biology that suggests young Pacific salmon are born with a sense of the earth’s magnetic field, which they use as a map to determine their location in the ocean. Unlike previous research, which suggested that salmon possess a memory of the magnetic field, Putman’s research revealed that long-distance navigation is an inherited trait in salmon.

“They know which way to swim as soon as they hit the saltwater,” he said.

In the study, Putman used salmon that had never set fin outside the testing facility – they had no opportunity to learn the large-scale, magnetic gradients of the Pacific Ocean because they had never been there. Researchers placed the salmon in five-gallon buckets within a wooden frame wrapped in copper wire. Running specific intensities of electrical current through the wires, researchers were able to mimic the magnetic intensities and inclination angles found in the Pacific. A camera overhead photographed the salmon as they swam in different directions based on the simulated magnetic displacements. On average, Putman said the fish swam in the correct direction based on the simulated displacement.

Putman said the study has several implications. First, researchers might be able to develop a clearer idea of salmon’s migratory routes by mapping their responses to different magnetic fields in a laboratory. Second, researchers might consider studying the effects of rearing salmon in artificial environments with distorted magnetic fields. These distortions may skew the ability of salmon to recognize their location once they get into the ocean, though Putnam said this depends on how fish calibrate their “magnetic map.”

“More broadly, the study suggests that the mysterious ability of animals to know where they are –and how to travel to places they’d like to go – might share a common, magnetic thread,” Putman said. “Our findings seem to mirror what we’ve observed in hatching sea turtles as well as other animals, ranging from newts to lobsters.”

Putman graduated in 2006 from The University of Alabama with a bachelor’s degree in biology and marine science. He completed in 2011 his doctorate in biology from the University of North Carolina at Chapel Hill. He will complete his postdoctoral research this year at Oregon State University, where he will remain as an affiliate faculty member.