Two male southern elephant seals clash over a harem. This photograph won the behavioral and physiological ecology category in the BMC Ecology photography contest of 2013.
Credit: Laetitia Kernaleguen
SAN FRANCISCO — Male elephant seals recognize the unique calls of their rivals, helping them know when to fight or flee, new research suggests.
The findings, presented here at the 166th meeting of the Acoustical Society of America, suggest that in the seals' hypercompetitive mating market, recognizing their rivals' calls to avoid senseless fights can be a good strategy.
"If you can call at your rival and save yourself from having to fight again, that's really good," said study co-author Caroline Casey, a graduate student in ecology and evolutionary biology at the University of California, Santa Cruz. That's smarter than "peaking early, wasting all your energy and being unable to carry on and having to sit on the sidelines for the remainder of the seasons."
For northern elephant seals, mating is risky business. The blubbery mammals come to Año Nuevo State Park in Northern California every winter, and the males battle violently over mates. The winners mate with several females, with the biggest, fiercest seals impregnating up to 50 females.
Meanwhile, the losers lurk around the fringes of the winning males' harems, hoping for a chance to impregnate an unguarded female. [Image Gallery: Elephant Seals of the Antarctic]
The fights — full of body slamming and slashing teeth — are dangerous and high stakes, because males must stay on the beach without eating or drinking for about 100 days during mating season. A loss can sideline them for the season due to malnutrition and energy depletion and can lead to permanent disfigurement, Casey told LiveScience.
Knowing when to fight or flee could help male elephant seals stay in the mating game. To see how they chose fights, Casey and her colleagues recorded the unique roars of elephant seals whose rank in the male pecking order was well known based on past interactions.
"The same male will emit the same call from year to year," she said, which even to the untrained ear sounds very different from another seal's call.
The researchers then played high- and low-status males' calls to a group of mid-ranking males.
When the seals heard the roar of a beta male, they approached aggressively. But when the male heard the call of a male higher in the dominance hierarchy, he turned tail and fled.
That suggested the seal knew the male's identity and that recognizing the call enabled him to decide how to respond.
In a follow-up experiment, the researchers went to a beach about 150 miles (240 kilometers) south and played the same calls to a group of elephant seals that weren't familiar with them.
The males didn't respond at all to the unknown calls. "This was a very anti-climactic field trip for us," Casey said.
That nonresponse suggests the elephant seals use prior knowledge of the pecking order to decide when to pursue or retreat from a fight. The scientists aren't sure whether the seals have to learn through painful personal experience which male is the alpha, or whether they can observe other fights to know when to steer clear, Casey said.