Internal ‘compass’
discovered in sharks

A UH find could aid future
studies of shark navigation

A University of Hawaii Shark Lab study has confirmed that sharks can detect changes in magnetic fields, but scientists do not know if this "compass sense" works as a navigation aid.

Still, the research conducted on Coconut Island in Kaneohe Bay might lead to a better understanding of how sharks navigate over long distances of open ocean. The study was published this month in the British Journal of the Royal Society Interface.

"Scientists have long suspected that sharks are able to use the earth's magnetic field to navigate across seemingly featureless oceans, but until now evidence of this compass sense has been circumstantial," said Carl Meyer, University of Hawaii Zoology professor.

In the study, six sandbar sharks and one scalloped hammerhead shark were conditioned to expect food in a particular area of their tank whenever an artificial magnetic field was activated. They went to the feeding area even when food was not present.

The magnetic field was between 0.7 and 2.8 times the intensity of the earth's magnetic field in Hawaii, too week for humans to detect, said Yannis Papastamatiou, a UH graduate student who participated in the study.

The research was conducted over six weeks at the Hawaii Institute of Marine Biology. The other researcher in the study is Kim Holland, head of the Shark Lab.

The study does not demonstrate whether sharks use their ability to detect magnetic fields for navigation.

But the existence of a compass sense should now make it possible to determine how the sense works, and how sensitive sharks are to the earth's magnetic field, Meyer said.

The theory of sharks' compass sense developed after researchers tracking blue sharks, tiger sharks and scalloped hammerheads in the 1990s observed them swimming in straight lines for long periods of time across open ocean.

Hammerhead sharks off Baja California were also observed using seamounts, where geomagnetic anomalies exist, as points of reference.