Orca whales in captivity can learn to imitate the sounds made by dolphins in order to facilitate cross-species communication and social interaction. That leaves American humans among the ever-dwindling number of species that can't be bothered to learn a second language.
A Thursday news release about a groundbreaking study published in the Journal of the Acoustical Society of America showed that orca -- Orcinus orca, sometimes called "killer" -- whales will change their speech patterns and the range of sounds they produce when kept alongside bottlenose dolphins, more closely aligning their speech to the dolphins'.
The technique of learning to imitate sounds and use them appropriately in social contexts is called "vocal learning," and it's a skill not solely limited to human beings. Some birds, bats and cetaceans -- marine mammals like dolphins and whales -- have shown an aptitude for vocal learning.
However, the new study -- produced by University of San Diego graduate student Whitney Musser and Hubbs-SeaWorld Research Institute senior research scientist Dr. Ann Bowles -- shows that orca whales who are socialized with bottlenose dolphins shift the types of sounds they made to more closely match those of the dolphins, their social peers.
Orca whales normally communicate by way of "clicks, whistles and pulsed calls," the study said. Pulsed calls are staccato bursts of sound punctuated by intervals of silence.
The pitches, durations and patterns of these sounds vary across social groups of whales, forming "dialects" that whales in certain sub-groups share.
Bowles said in the news release, “There’s been an idea for a long time that killer whales learn their dialect, but it isn’t enough to say they all have different dialects so therefore they learn. There needs to be some experimental proof so you can say how well they learn and what context promotes learning.”
Bottlenose dolphins are a good study group to pair orca whales with, the scientists said, because their language consists of similar clicks and whistles as the orcas, but they do not use the whales' pulsed calls.
“We had a perfect opportunity because historically, some killer whales have been held with bottlenose dolphins,” Bowles said.
The team compared recordings of cross-socialized whales and dolphins to recordings of animals kept in their own species groups and found that the orcas who were socialized with dolphins "spoke" more like dolphins. The cross-socialized whales used far fewer pulsed calls and communicated with more dolphin-like clicks and whistles.
Furthermore, the team found evidence that orca whales could be trained to make entirely new sounds. One female orca was taught a pattern of chirps by human caretakers that her dolphin pool-mates were taught before she came to live with them, so that when they met, they had the sequence in common.
Vocal learning in and of itself is not evidence that orca whales use language in the way that humans do, the team cautioned, but is evidence of neural plasticity in the animals, an ability of their brains to adapt to new tasks and change how information is interpreted and handled.
"Killer whales seem to be really motivated to match the features of their social partners," Bowles said, although it's currently unknown what evolutionary purpose the ability serves.
She went on to say that understanding how cetaceans learn and communicate is a doorway into learning how to help their populations avoid the hazards of commercial fishing nets, toxic chemicals in ocean water, oil spills and other hazards that threaten the species' survival.
"It's important to understand how they acquire [their vocalization patterns], and lifelong, to what degree they can change it, because there are a number of different [cetacean] populations on the decline right now," said Bowles. "And where killer whales go, we can expect other small whale species to go -- it's a broader question."