"These results are consistent with the idea that juvenile salmon imprint on (i.e. learn and remember) the magnetic signature of their home river, and then seek that same magnetic signature during their spawning migration," said Nathan Putman, a post-doctoral researcher at Oregon State University and the lead author of the study.
It has long been known that some animals use the Earth's magnetic field to generally orient themselves and to follow a straight course. However, scientists have never before documented an animal's ability to "learn" the magnetic field rather than to simply inherit information about it or to use the magnetic field to find a specific location.
This study provides the first empirical evidence of magnetic imprinting in animals and represents the discovery of a major new phenomenon in behavioral biology.
In addition, this study suggests that it would be possible to forecast salmon movements using geomagnetic models--a development that has important implications for fisheries management.
Get out the map
Putman says scientists don't know exactly how early and how often salmon check the Earth's magnetic field in order to identify their geographic locations during their trip back home. "But," he says, "for the salmon to be able to go from some location out in the middle of the Pacific 4,000 miles away, they need to make a correct migratory choice early--and they need to know which direction to start going in. For that, they would presumably use the magnetic field."
Putman continues, "As the salmon travel that route, ocean currents and other forces might blow them off course. So they would probably need to check their magnetic position several times during this migration to stay on track. Once they get close to the coastline, they would need to hone in on
|Contact: Lily Whiteman|
National Science Foundation