In a study published this week in the journal Royal Society Open Science, UC-Santa Cruz biologists show that the massive animals, which weigh more than two tons, develop unique vocalizations that males can use to decide if and when to pick a fight with a rival.
The researchers have been getting up close and personal with the potentially dangerous animals, recording their calls.
“I equate it to feeling like you’re in Jurassic Park or something,” Caroline Casey, a UC-Santa Cruz graduate student, said in a video. “You’re only 30 minutes away, but it feels like you’re in a completely different universe. This is their world, and you get to be sort of a fly on a wall.”
Twice a year the seals will wriggle their jiggly bodies onto the beaches of Ano Nuevo, Calif., once for mating and again for a “catastrophic molting” of the outer-layer of their skin. The lucky alpha males attract harems of 30 or 40 females while their beta counterparts compete for whatever love they can get. The bigger the male and his floppy trunk-like nose, the better his chances with the ladies.
It’s the perfect chance for researchers to study their vocal behaviors, called “clap threats,” as well as their violent physical interactions. In the most intense moments, the males rear up and slam their chests into each other, bite ferociously, sometimes bleeding all over themselves.
But the key to the whole system is the noise each seal makes.
“Anybody who’s studied elephant seals knows that their vocal communications are important, but we haven’t known what information is encoded in the vocalizations,” Casey said in a statement.
Over the course of four breeding seasons, the researchers used acoustic analysis and found that males responded aggressively to subordinate males, but retreated when hearing the call of a dominant rival. It’s a good system to keep the peace, with only about 5 percent of interactions leading to physical contact. That’s important for the animals, who must conserve energy and avoid potentially fatal encounters with rivals if they want the chance to breed some day.
When the scientists played the recorded calls near males of a separate population, however, the animals barely budged.
“They either ignored the speaker or seemed hesitant to respond, like they were looking for more information,” Casey said.
So it appears the seals’ strange gurgling actually means something specific to the animals, which is remarkable considering they encounter around 43 opponents over the course of a single season. In the end, the mating struggle is really not so much a free-for-all after all.
“There is a very structured social network among the males in a given location,” said Colleen Reichmuth, a research biologist at UC-Santa Cruz.
Elephant seals are the largest seals in the world, with males weighing in at more than 5,000 pounds. They were almost hunted to extinction a hundred years ago for their blubber, but they have recovered. While they are still considered a threatened species, their numbers are growing.