Prince William Sound, Alaska, where a gray whale swims by. The species usually lives in the Pacific Ocean, but has also recently been found in the Atlantic. Photo by NATURE PICTURE LIBRARY, ALAM
Written by: HEATHER RICHARDSON
The male gray whale was spotted near Namibia in 2013, the first time the species has appeared in the southern hemisphere.
A study recently published in Biology Communications pointed out that after several years of genetic research, it was finally confirmed that the gray whale came from the North Pacific.
Gray whales currently have two known populations: the Eastern Pacific Gray Whale and the Northwest Pacific Gray Whale. The former is stable, with about 20,500 heads; the latter is endangered, leaving only about 200 wild individuals, mainly due to decades of commercial whaling. The Eastern Pacific Gray Whale generally migrates from the waters near Alaska and Russia to its breeding grounds in Baja California. Little is known about the breeding grounds of the Northwest Pacific Gray Whales, but there are records that they forage near eastern Russia.
In 2013, Simon Elwen, a zoologist at Stellenbosch University in South Africa, first heard of the presence of gray whales in Namibia, "a little dismissive," he said. "It's like someone saying they saw a polar bear in Paris – technically saying it can get there, but that doesn't seem very realistic."
The photos confirm that it is indeed a gray whale, about 12 meters long. Probably due to malnutrition, it spent two months in Walvis Bay, where Elwen and colleague Tess Gridley had the opportunity to collect minimally invasive DNA samples.
The gray whale set a new swimming record, the previous record holder was a leatherback turtle, it traveled 20,550 kilometers in the Pacific Ocean, the birth of a new record also raised the question of scientists: Why is this gray whale so far away from home?
The study co-authors speculate that due to climate change, Arctic sea ice is rapidly decreasing, so gray whales may explore or get lost in new habitats, but there is not enough data to draw any conclusions.
For whales that typically migrate around 8,000 kilometers, "it comes at a great cost to swim such a long distance," said study co-author Rus Hoelzel, an evolutionary biologist at Durham University in the United Kingdom and an explorer at National Geographic. "It does make you wonder why they did it, and under what circumstances did they make such a move?" It has also stimulated our scientific interest. ”
Delve into genes
To better study, Gridley and Elwen teamed up with Hoelzel and Fadeh Sarigol, an evolutionary biologist at Durham University, to compare the gray whale's genome with that of other gray whale genomes stored by the National Center for Biotechnology Information, which stores the genomes of more than a thousand organisms.
The genetic comparison was made to rule out the possibility that it came from an unknown Atlantic population; there is fossil evidence of gray whales in the Atlantic, where in recent years two gray whales have been found in the North Atlantic and the Mediterranean.
"We know very little about some cetacean species because it's hard to encounter them," Hoelzel said. "But in the case of gray whales, they do tend to live in coastal areas and are very easily recognizable, so the idea that this hidden population exists in the Atlantic ocean is unlikely to hold."
It turns out that the genes of the whale found in Namibia did indeed match those of the North Pacific gray whale stored in the biotechnology database. The researchers said it was surprising that the most matched was the northwest Pacific gray whale.
Wandering whales?
Next, the team analyzed the possible route of the marine mammal, believing it was most likely to bypass Canada from the Northwest Passage. Other routes, such as circumnavigating South America or swimming across the Indian Ocean, are less feasible, in part because of the lack of eyewitness reports and because gray whales tend to forage in shallow waters, making it difficult for them to travel long distances on the high seas.
However, Sue Moore, a scientist at the University of Washington in Seattle who specializes in marine mammal research in the Pacific, believes that crossing the Indian Ocean is the most likely because the road is the shortest and easiest to pass.
"That is... The whale is likely to be a wanderer," Moore added, adding that it was not a migration with a clear destination. She was not involved in the study.
"But," she said, "it did give us some really interesting thoughts about the resilience of this species." ”
(Translator: Strange Flowers Blossom)