Jason Bruck knew from the age of 3 that he wanted to work with marine mammals when he grew up. He remembers his awe on a childhood whale-watching outing as a massive humpback whale and its calf stopped and looked him in the eye from just a few feet away.
“You can’t have that kind of experience with any other animal,” says Bruck, PhD’13. “They’re so unknown, so powerful. When you come out to see a whale in its element and you see something like that, it shapes you, especially at that formative age.”
Bruck took an arduous path to realize his dream of working with marine mammals, including years of struggle with learning disabilities that threatened to derail his schoolwork. But his efforts came to fruition this summer, as he received international notice for a new study showing that dolphins have the longest social memories of any nonhuman species — more than 20 years, in some cases. The paper in Proceedings of the Royal Society B was published a couple of months after Bruck received his PhD from UChicago’s Department of Comparative Human Development.
He found that dolphins can recognize their old tank mates’ whistles even after decades of separation. The remarkable memory feat is another indication that dolphins have a level of cognitive sophistication comparable to only a few other species, including humans, chimpanzees, and elephants. Dolphins’ talent for social recognition may be even more long-lasting than facial recognition among humans, since human faces change over time, but the signature whistle that identifies a dolphin remains stable over many decades.
“This shows us an animal operating cognitively at a level that’s very consistent with human social memory,” Bruck says.
Scientists take notice
Bruck’s findings earned widespread news interest, and spurred new questions among researchers who study dolphin cognition. The striking durability of dolphins’ memories came as a surprise to Peter Tyack, a marine-mammal biologist at the University of St. Andrews in Scotland.
“I would not have been surprised if [dolphins] started to forget the whistles of some pool mates five to ten years after they were separated,” Tyack told a reporter for the journal Nature.
In recent years, other studies established that each dolphin develops a unique signature whistle that appears to function as a name. Researchers Vincent M. Janik and Stephanie L. King, also at St. Andrews, reported earlier this year that a wild bottlenose dolphin can learn and repeat signatures belonging to other individuals, and answer when another dolphin mimics its unique call.
King told the Associated Press that Bruck’s work “hints at the wider importance of long-term social memory in nonhuman mammals, and suggests there are strong parallels between dolphin and human social recognition.”
'Signature whistles' offer means to test memory
To establish how well dolphins could remember their former companions, Bruck collected data from 43 different bottlenose dolphins at six facilities. He played recordings of signature whistles to dolphins that had once lived with the animals that made the calls. Determining whether the dolphins recognized their old companions required a methodical comparison of how they responded to familiar calls versus calls belonging to dolphins they had never met.
The familiar calls often would perk up the dolphins and elicit an immediate response.
“When they hear a dolphin they know, they often quickly approach the speaker playing the recording,” Bruck says. “At times they will hover around, whistle at it, try to get it to whistle back.”
A clear pattern emerged in the data: Compared with unfamiliar calls, dolphins responded significantly more to whistles from animals they once knew, even if they had not heard the calls in decades.
A different road to creativity
Bruck’s promising career as a scientist would have seemed unlikely to some of his teachers in grade school. He contended with undiagnosed attention deficit hyperactivity disorder until the sixth grade, when his mother came across a book on the condition and realized he must have it. Sitting still in class and following a teacher’s lecture were almost impossible for him; he could not master reading or writing until the fourth grade.