JUANA SUMMERS, HOST:
Elephant seals are huge, gray and blubbery. They have a big snout and a very distinctive voice.
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SUMMERS: But despite the obvious differences, elephant seals actually have something in common with humans - they don't forget their enemies. Researchers from the University of California, Santa Cruz say male elephant seals remember their competition from previous breeding seasons. Caroline Casey presented this research at a recent conference in Hawaii and joins us now. Hi there.
CAROLINE CASEY: Hi there. Thanks for having me.
SUMMERS: Thanks for being here. So Caroline, I know you have been studying seals for more than a decade, so I just want to start off with a super basic question. What makes an elephant seal different from other seals?
CASEY: Oh, my gosh. I mean, for me, elephant seals are one of the most amazing animals in the animal kingdom. But among seals they are, you know, some of the deepest divers of any seals. They're one of the largest of all the seal species. They're the most sexually dimorphic, meaning that males look different than females. And to me, they have one of the most interesting breeding systems.
SUMMERS: Interesting. OK, so how did you discover that elephant seals remember the calls of their rivals?
CASEY: Yeah. This is a really long-term study that me and my colleagues have been evaluating for the past 13 years at Ano Nuevo State Park, located in California. So at that site, we track individual male seals. Once they arrive on the breeding beaches - you know, elephant seals go on these amazing foraging migrations, and they spend most of their life at sea. But each year, they come back to the same sites every year to breed. And the males arrive first, and they fight for access to breeding opportunities. So once they arrive, our colleagues and I start tracking them. And we have just discovered so many amazing things about them, including the fact that they have these unique voices. We've done lots of experiments that demonstrate that each male has a unique voice or name...
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CASEY: ...That they learn and remember during the breeding season to cut down on the costs associated with fighting because they don't want to be fighting all the time, but they need to remember who one another is. And so to do that, they basically have names.
SUMMERS: Can you talk a little bit about how you conducted this research and how you specifically worked with those unique sounds that elephant seals make?
CASEY: Yeah, sure. So from our previous research, we knew that males will respond deferentially depending on the dominance status of the caller. So, for example, if a male within a season hears his most dominant rival, he'll run away, even in the absence of the male being there themselves. And if he hears his most subordinate rival, he'll sometimes attack or go towards the speaker or the sound. And so we would track males at - in - during one year we would record his most familiar dominant rivals, and then we would try to find him again the next year and play back the sounds of his familiar rivals.
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CASEY: And what we wanted to know was - are these males responding the same way that they would have in the previous year or is everything being reset or they don't maybe recall those signals over time? So those were the types of questions that we were asking.
SUMMERS: I want to ask, do you have a favorite, like, individual seal?
CASEY: Yes. You played him at the beginning of your intro, and I'm so happy you did (laughter). It's X579.
SUMMERS: X579 - that's his name?
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CASEY: Yes, that's his name. And he has such a unique call, and he just was one of these males that came back every year. He started out as, like, this kind of subordinate, not very dominant male, worked his way up the dominance hierarchy and then was a dominant male for three years, three consecutive seasons. So he's just this, like, incredible success story. So few males ever get to breed. You know, less than 5% of males born ever attain breeding status or become what we call alpha males. And so he's just - I loved him. He was great.
SUMMERS: That's Caroline Casey, a research scientist at the University of California, Santa Cruz. Thanks so much.
CASEY: Yeah, thank you for having me. Transcript provided by NPR, Copyright NPR.
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