HONOLULU, Dec. 1, 2025 — How would you react if you overheard the voice of a long-lost friend or old co-worker? Chances are, just the sound of their voice will bring back memories of times you spent together. Humans are not the only animals that can remember the voices of their old acquaintances. Elephant seals, too, can remember the calls of their rivals even a year later.
Caroline Casey, research scientist and adjunct professor at the University of California, Santa Cruz, will present her team's research on elephant seal memory Monday, Dec. 1, at 2:45 p.m. HST as part of the Sixth Joint Meeting of the Acoustical Society of America and Acoustical Society of Japan, running Dec. 1-5 in Honolulu, Hawaii.
Casey and her team have spent over a decade studying the seals on Año Nuevo Island off the coast of California. They have observed male elephant seals engaging in dominance displays year after year, and it led them to wonder if the seals remembered their past bouts.
"Male elephant seals come back to the exact same breeding location year after year and engage in competitive interactions with a number of familiar individuals," said Casey. "It would make sense, then, that they would retain some memory of past rivals over multiple seasons."
To test this, the team would find a male seal returning to the island at the start of the mating season and play recorded calls from his old rivals.
"When males heard their most familiar dominant rival from last year, they tended to orient faster, exhibit a faster posture change, and often would retreat from the speaker," said Casey. "Their responses were less severe when they were presented with their subordinate rival from the previous season, and sometimes they would even approach the speaker."
They also played calls recorded at other colonies, observing that these unfamiliar calls elicited a much smaller response from the seals. This proved that the seals were not just responding to random strangers but actually recognizing and remembering individuals they had met the year prior.
The researchers are continuing to study elephant seal reproductive behaviors.
"Right now, we are working on a project evaluating the traits that lead to eventual reproductive success in male elephant seals," said Casey. "Essentially, what does it take to become an alpha seal? We are measuring lots of different aspects of behavior and physiology and linking it to true reproductive success in this species."
