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Turns Out, Male Elephant Seals Know Each Other's Voices

Caroline Casey's recent research on Northern male elephant seals led to a neat discovery—males recognize each other's calls, leading them to play it safe during fights.

by Madeleine Turner

March 15, 2016—Two male elephant seals rear up, meeting each other chest to chest. They pound their upper bodies together and take toothy digs at each other’s necks. There’s blood. During fights, alpha males want to check subordinate males and subordinate males just... keep trying. Or do they?

Fights cost a male his energy and health. So to discourage conflict, a male puts on a display. He arches his back, throws back his head, and begins to roar, emitting a throaty bellow. This display is predictable and automatic, like a sneeze. He’s telling other males: don’t try me.

But how do other males decide whether to heed his warning? That’s the part people didn’t understand until now. Caroline Casey, Ph.D. candidate at UC Santa Cruz, studies these display calls to pin down the exact reason for why they work.

Before Casey’s research, scientists thought maybe males discerned their rivals’ physical size from certain qualities in their calls—like assuming a deep voice belongs to a tall man.

But that’s not what’s actually going on. Instead, Casey found males recognize their foe’s unique voice. They associate other males’ calls with past wins and losses. Says Casey, “This suggests males know each other fairly well.”

Collecting Clues
Casey and her team studied seals at Año Nuevo State Park between 2009 and 2013. First they categorized males as either alpha, beta or subordinate. Males who won fights and controlled harems (a group of 10 to 20 females) were alphas. Betas were lower in status—sometimes they won fights and snuck into harems. Subordinates lost fights and couldn’t get near females; they were usually younger males.

The team did research December through February, during breeding season. Most fights happened in December, while males were arriving and trying to establish dominance. After that, males put on displays but rarely fought.

The team also recorded male calls and took their measurements. They used powerful microphones and stood a safe 15 feet back. Luckily no measuring tape was involved either—the team snapped photos of males and used a software program to compute their size.

Then they analyzed display calls. Male elephant seal voices sound like gurgling mud and can be analyzed as a series of clicks. The team measured these clicks and pitch. Judging by these two qualities, each male does have a unique call, which suggests it’s possible for one male to recognize another.

They also compared males’ calls and dominance to their physical size. There were some connections between calls and size. But the team also realized that size doesn’t determine dominance. This is counterintuitive—why don’t the biggest and baddest claim alpha status? It’s because very few males survive to adulthood—10% or fewer. Casey explains, “Once you’ve made it to adulthood, there aren’t huge discrepancies in size. ” Therefore it wouldn’t be that useful to “hear” whether your opponent is slightly larger or smaller, even if that information is embedded in his call.

Read about an average human's day-trip to see the seals.

Call to Action
These were useful hints, but none of it was definitive proof that males recognized each other. To find proof, the team played back their recordings of calls to males. When they played calls of a familiar subordinate male to a beta male, the beta would lunge, ready to fight his invisible opponent. But when they played calls of a familiar alpha male, beta males would retreat. Alpha males ignored calls unless they were nearby, in which case the alphas got aggressive.

Next the team played recordings of unfamiliar opponents—males from San Simeon, a rookery two hundred miles south of Año Nuevo. Alpha males ignored these calls. But betas retreated—it didn’t matter whether calls were from subordinate or alpha males. Basically, betas were dumfounded—they were never acquainted to these callers and therefore avoided engagement.

“I was really happy that we’re able to confidently conclude what those calls are really used for,” says Casey. “There’s a lot of learning [for males] involved in this process, which opens a new set of doors for interesting questions to ask.”

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