Sperm whales in the Pacific Ocean emit distinct vocalizations that help them identify whales in different clans, according to a new study from a team including a researcher from Oregon State University.
These vocalizations, called “identity codas,” are unique sequences of Morse code-like click sounds that function as symbolic markers of different social groups and are indicative of whale culture, the researchers say.
“They all kind of use the same language, but express things slightly differently,” said Mauricio Cantor, assistant professor at OSU’s Marine Mammal Institute and co-author of the study,publishedlast week in PNAS. “As symbolic markers, identity codas would serve as a flag: an arbitrary but useful means of announcing membership in a particular group.”
Cantor compared the use of ID codas to a human wearing a football shirt: if you’re at a game but don’t know anyone in the crowd, a shirt is a simple way to tell everyone in which group you are.
Codas are a sign of whale culture as they are shared among clan members, learned and passed down from generation to generation via social learning, he said. Calves are not born knowing specific codas, but they learn them by imitating adult members of their clan. And the clan codas have remained consistent over time.
“The big picture here is this gigantic gap that we perceive (or insist on perceiving) between humans and everything else on Earth,” Cantor said. “One of the main things that used to separate us is the ability of humans to have a culture. This notion is slowly eroding over time with studies showing that animals learn and they pass that information on, which can become small stable traditions over time.
This gap is further bridged by new evidence that whales use arbitrary behaviors as symbols of cultural group membership, as such symbolic markers are universal in human cultures but are thought to be very rare in animal cultures, said singer.
For the study, led by Taylor Hersh of the Max Planck Institute for Psycholinguistics in the Netherlands, researchers analyzed 23,429 sperm whale codas recorded in 23 specific regions of the Pacific Ocean. Records date from 1978 to 2017 and span from Tonga, Palau and Japan to Chile and the Galapagos Islands.
By listening to the different sounds of the whales, the team discovered a previously unknown clan and named two lesser-known clans for the first time. Prior to this study, there were four well-known clans, but the unique codas identified by this team proved that there were at least seven distinct clans in the Pacific, and possibly more in less studied regions.
All sperm whales have a wide repertoire of vocalizations, including non-identifying codas that whales of all clans use, Cantor said. But by analyzing the vocalizations in geographic terms, the researchers were able to isolate the specific identity codas that each clan uses to distinguish themselves.
They found that identity coda use was more distinct in areas with greater spatial overlap between multiple clans, and less distinct in areas where individual clans were more isolated.
So in areas where a certain clan knows it’s the only one in town, whales seem to be more relaxed in the types of codas they use, compared to crowded areas where they wouldn’t necessarily know if a whale to proximity is part of their clan, Cantor explained.
The seven identified Pacific clans are named for their special coda sounds. For example, the“Usual”the clan has a series of clicks at a constant rate while the “Plus One” clan has a slight pause before the last click of a sequence; as well as the “Four-Plus”, “Short”, “Rapid Rise”, “Palindrome”, and “Slow Rise” clans.
The Marine Mammal Institute is based at OSU’s Hatfield Marine Science Center in Newport, Oregon, which is part of the university’s Department of Fish, Wildlife, and Conservation Sciences in the College of Agricultural Sciences.
Other co-authors of the paper include Shane Gero from Carleton University in Canada, Hal Whitehead from Dalhousie University in Canada and Luke Rendell from the University of St. Andrews in Scotland, along with 22 other researchers working across the Pacific.