How Culture Guides Belugas' Annual Odysseys Across the Arctic

Science
پنجشنبه 23 فروردین 1397 ساعت 22:41
398
Smith sonian mag
The belugas were due to arrive in droves, but Gregory O’Corry-Crowe was nervous. Just a few years into a postdoctoral biology fellowship, O’Corry-Crowe had taken this opportunity in 1998 to fly to remote Somerset Island in the Canadian Arctic with a pair of seasoned biologists. Would the whales show up?
The whales were not shy about announcing their arrival. After a few days of relatively quiet seas, they roused him in the early hours—night this far north was only a dim concept in the summer—with a “cacophony of noise” caused by their blowing, flapping and humming in the water. O’Corry-Crowe rolled out of his sleeping bag at the seaside camp to a vista of about 1,500 beluga whales.
“That was one of those breathtaking, speechless kinds of moments,” says O’Corry-Crowe, now a research professor at the Harbor Branch Oceanographic Institute at the Florida Atlantic University. That surreal experience was one of the factors that drove him to spend 20 more years studying belugas and their migration patterns.
And if there's anything he's learned over a career spent drawing together Canadian, American and Russian research on these animals, it’s that he probably had little reason to be nervous about the whales’ arrival on Somerset all those years ago: The belugas always come back.
Determining why has led O’Corry-Crowe and his coauthors to publish a recent study in PLOS ONE finding that north Pacific beluga whales depend on strong, multi-generational cultural ties to help guide their migrations to traditional summer locations across the Arctic. The study on beluga culture joins an emerging line of research which has so far focused on orcas and sperm whales, and expands the common understanding of what constitutes “culture” beyond the realm of humans and other primates.
To understand the significance of these findings, you first have to ask: what is culture? For the purposes of the research, O’Corry-Crowe defines it as “knowledge or behavior that is shared within a group or society of individuals which is acquired from conspecifics through some sort of social behavior. They are acquiring this information through group members in a kind of teaching-learning kind of way.”
The data set the authors pulled together was unprecedented, combining decades of genetic research, traditional indigenous knowledge, and satellite tracking data. Using it, they determined for the first time that beluga whales from the same families usually return to the same summer grounds for generations and likely inherit their migratory behavior.
While that might remind you of salmon, which return to their birthplaces to spawn again by following chemical cues in the water, O’Corry-Crowe believes there's far more at play with belugas.
“It is possible that chemical cues may also be involved in migratory patterns of other vertebrate species, including possibly whales,” he says, “but we believe that some sort of social learning is at play here that requires stable close associations among group members in the acquisition of migratory knowledge and behavior.”
Belugas have strong multi-generational ties, which help them find traditional migration spots year after year. (Gregory O’Corry-Crowe)
They found that north Pacific white whales ("beluga" means white in Russian) take a migratory route through the Bering Sea. Depending on the population, they spend their winters off the western and southern coast of Alaska and the eastern coast of Russia.
During the summer, many belugas travel north through the Bering Strait to the waters off the north coast of Alaska and the Canadian Arctic while other groups move less, shifting their activity into Russian and Alaskan inlets. The marine mammals will diligently follow the same patterns year-by-year, only shifting when the sea ice is quite different from average conditions.
“We realize now that these animals undergo this incredibly complex annual odyssey and probably navigate a lot of challenges along on the way. In the process, we think they are forming these lifelong associations with close kin to help them navigate the challenges and basically succeed in life, whether it’s to breed, or feed or molt,” O’Corry-Crowe says.
Part of this culture likely comes from a long upbringing and lifespans comparable to those of humans. Beluga calves are known to stay with their mothers for two to three years. “You can see how this is where they’re learning the ropes,” O’Corry-Crowe says.
The finding is perhaps surprising because beluga groups aren’t necessarily as tightly knit as orca pods sometimes are, and plotting a map of their migratory behavior can sometimes look chaotic. Groups can vary from pods of 40 to 50 animals to herds numbering in the thousands, such as those O’Corry-Crowe witnessed off Somerset Island. The groups are often made up of related family members, but when they migrate, different groups can intermingle, sometimes partaking in “promiscuous” travel behavior.
In many ways the research is a confirmation of traditional knowledge from indigenous people living in the U.S., Canada and Russia. Groups like the Yupik and Iñupiat have long believed the belugas and their families return to the same spots every year. “A lot of the questions we tackled are actually driven by their interest and their concern with their environment,” O’Corry-Crowe says.
More and more researchers are beginning to listen to indigenous beliefs and knowledge about whales. The Yupik in particular held that belugas longed to return to land, and gave their bones ritualistic treatment after hunting to allow them to make this transition, according to a recent article in Hakai Magazine .
Amy Van Cise , a post-doctoral scholar at the Woods Hole Oceanographic Institution, studies social structure, genetic relationships and dialects among different groups of short-finned pilot whales in the Pacific. She says that theories about a migratory culture have been around for a while, but this multi-decade examination brings a lot of this theory together.
“(Their) results support this idea that people have had for a long time, that there is a strong link between culture and genetics in social cetaceans,” Van Cise says.
Other whales, like orcas, have been studied extensively for decades, meaning much more is known about the cultural evolution of different social groups and how that might influence their genetic evolution. "But we have a lot less information about belugas in that way,” she says. The new study makes it clear that “migratory culture is an important part of the evolution of beluga whales.”
O’Corry-Crowe says that belugas have a very diverse diet in general, including arctic cod, crustaceans and migrating salmon in the summer. He also noted that populations in different areas feed on different prey, but there is no evidence yet of specific learned feeding strategies associated with those different groups such as with orcas.
While culture may be helping beluga whales find their way through the Pacific and Arctic oceans now, O’Corry-Crowe does worry about whether multi-generational cultural learning can adapt to long-term environmental shifts caused by climate change—or whether it will lead whales back to the same traditional spots, even as they become inhospitable.
“You could see how culture has this two sides to it,” he says. “Will it be a liberator or will it hold them hostage?”
لینک اصل محتوا در Smith sonian mag
برچسب ها