Gray whales spend their summers in the chilly waters of the northern Pacific and their winters along the coasts of California and Mexico. So researchers were surprised to hear reports of a lone gray whale spotted in the southeastern Atlantic off the coast of Namibia.
The whale had traveled halfway around the world, and likely set a new record for the longest in-water migration, Heather Richardson reports for National Geographic. Now, new research published in Biology Letters presents a genetic analysis of the whale that suggests it originated from a very small population of gray whales in the western Pacific.
When University of Stellenbosch zoologist Simon Elwen first heard of the sightings of the whale in 2013, “I was a bit dismissive,” he tells National Geographic. “It’s like someone saying they saw a polar bear in Paris—technically it could get there, but it just doesn’t seem very realistic.”
But photographs confirmed the sighting: the 40-foot-long male gray whale spent about two months in Namibia’s Walvis Bay. During that time, Elwen and Tess Gridley, also a zoologist at the University of Stellenbosch, gathered minimally invasive DNA samples from the wayward whale.
Gray whales are well-known for their impressive migrations that bring them from the Arctic in the summer to the coasts of California and Mexico in the winter. While the whales were once common around the world, commercial hunting reduced their population dramatically. The Pacific ocean’s eastern gray whales made the strongest recovery, and their population is now about 21,000 individuals—down from 27,000 five years ago.
The new study presents genetic evidence that the gray whale spotted off of Namibia made its trip from the much smaller western Pacific population, which has only a few hundred individuals. Based on that origin, the researchers presented three possible routes that the whale could have taken to reach the southeastern Atlantic.
The most likely path, according to the paper, would have taken the whale around Canada in the north, across the Atlantic and then south along Africa’s west coast—that would be an impressive 16,700-mile journey.
“This is the record really for an in-water migration, if you’re assuming that this individual started its life in the north-west Pacific and it found its way to Namibia,” says co-author Rus Hoelzel, an evolutionary biologist at Durham University, to New Scientist’s Krista Charles. “That’s as far as any vertebrate has ever gone in water, as far as we know.”
Usually gray whales’ migration is only about 10,000 miles round-trip, which already blows land-dwelling mammals out of the water. The record for the longest migration for a mammal on land is about 4,350 miles traveled by a gray wolf, per New Scientist. The previous record-holder for longest migration by water was a leatherback turtle that swam 12,774 miles across the Pacific, per National Geographic.
At this point, it is not clear whether the gray whale made its trip on purpose, or accidentally wandered into the Atlantic, Hoelzel tells Der Spiegel. Because average temperatures are rising about three times faster in the Arctic than the rest of the globe, new paths have likely opened in the sea ice that the whale used to travel around Canada.
However, University of Washington marine mammal expert Sue Moore tells National Geographic that she thinks a route along the coast of eastern Asia and the Indian Ocean, which would be 11,000 miles, is more likely than the 16,700-mile route.
“At the population level, what’s interesting is that we are seeing a lot of changes in the environment that have to do, in this particular case, with the opening up of the Arctic Ocean due to climate,” says Oregon State University oceanographer Daniel Palacios, who was not involved in the study, to New Scientist. “It goes beyond this one animal to potentially many animals doing the same thing.”