Gray whales have the longest known migration of any mammal, travelling up to 12,000 kilometres round-trip every year between their winter calving grounds in Mexico and summer feeding grounds in the North Pacific. No one is exactly sure how they navigate over such vast distances, but new research suggests they could have an internal compass that is attuned to Earth’s magnetic field.
A team led by Jesse Granger, a graduate student at Duke University, looked at data on gray whale strandings between 1985 and 2018. In some cases, the stranded animals were found to be ill or injured, but sometimes they just seemed to have made a navigational error. What could have caused them to veer off-course?
The data the team collected found that strandings occurred more often on days with solar storms, suggesting that intense solar activity might make it difficult for whales to find their bearings.
There are two possible reasons for that, Granger says. The first is that strong solar storms distort and temporarily weaken Earth’s magnetic field, so whales that may be used to following a fixed path could become confused. The second is that solar storms release a lot of radio frequency (RF) noise, which prevents certain animals from assessing magnetic fields.
An ability to sense the geomagnetic field, called magnetoreception, has been documented in a number of animals. Migratory birds orient to Earth's magnetic field when blue-to-ultraviolet light stimulates a protein called cryptochrome present in their eyes. This protein has been found in dogs and foxes as well.
Granger says more research needs to be done to determine whether whales are actually magnetoreceptive.
“This research is a correlation study, and you can’t ever say from a correlation study that we know one thing is causing the other,” she says, adding other major causes of whale stranding include food shortages, entanglement in fishing gear and being hit by vessels.
“We’re not saying solar storms are the only cause of stranding or a major cause of stranding. We’re saying they might be an additional factor.”
For Granger, the next step is to look for similar correlations between strandings and solar storms in other whale populations across the continent and around the world.
“I feel like we really haven’t answered any question yet,” she says. “We’ve only posed more.”