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A study of nearly 200 strandings of healthy grey whales over the past 30 years has found that the animals are four times more likely to strand themselves during solar storms.

Jesse Granger at Duke University in North Carolina and her colleagues think that radio frequency noise produced by the storms interferes with the magnetic compass of whales, preventing them from sensing direction.

But her team has shown only a correlation between the two events, Granger stresses. 鈥淭his is not direct evidence,鈥� she says.

We still know little about how whales navigate in largely featureless oceans during their long migrations. It is likely that they use magnetoreception as many other animals do, but this is difficult to demonstrate.

To investigate, Granger and her team looked at 186 instances where individual grey whales with no signs of any injury or interaction with people had become stranded, presumably due to navigational errors. They found strandings were twice as likely on days with more sunspots.

Sunspots are associated with solar magnetic storms that can affect Earth鈥檚 magnetic field and make magnetic compasses point in the wrong direction. But the team found no link between deviations in Earth鈥檚 magnetic field and strandings.

However, strandings were four times more likely on days when high levels of radio frequency noise due to solar activity had been measured. This fits in with the hypothesis that a protein in animals鈥� eyes called cryptochrome is involved in sensing magnetic fields. If so, the mechanism thought to be involved would be disrupted by radio frequency noise, effectively blinding animals to magnetic fields.

Several previous studies have suggested that solar activity can affect the navigation of animals. One showed that , says Granger. There is also some evidence that .

Even if solar activity does make strandings more likely, it certainly isn鈥檛 the only cause. 鈥淭here are a huge number of reasons why whales strand,鈥� says Rob Deaville of the UK Cetacean Strandings Investigation Programme.

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