News and notes on science
If you’re a beta northern elephant seal and you hear one sound, you might run.
But when you hear another sound, you might scratch your head and wait to see what happens.
And here’s why: In the rhythm and pitch of the first call, you recognize one voice as a familiar, more dominant male that you have fought with before. But you can’t discern the other, modified call, according to a study published July 20 in Current Biology. This suggests that elephant seals are the only known mammals other than humans that can use rhythm to recognize and respond to other members of their species in the wild.
During breeding season, between December and March, elephant seals take a break from their lives at sea and congregate on the West Coast from San Francisco to Mexico. The males, called bulls, arrive first and fight to establish dominance. Winning males become alphas with a whole harem of females with which they can breed. Losers become betas, connecting with females only opportunistically, when the alphas aren’t around and dominating other males that are even lower in the hierarchy.
At Año Nuevo State Park in Pescadero, Calif., the researchers recorded calls from elephant seals up and down the hierarchy. Later, they returned to the beach with calls they had altered in the lab. They set up speakers a foot tall a few yards from the seals and played back the original and modified calls of alpha seals to beta seals.
The team found that the subordinate seals recognized the rhythm and pitch of the original dominant individual’s call and fled.
But when the researchers manipulated the original call, sliding the pitch higher or lower or the rhythm faster or slower — by just a little so it still resembled a seal — the subordinate seals reacted to the modified calls just as they would the calls of strangers: They waited to see what type of interaction would follow.
This is the first study to experimentally demonstrate that a nonhuman mammal can use the rhythm of another’s voice to make decisions that affect survival.