Seals use 'voice recognition' to identify rivals

Male elephant seals can identify the strength and status of their rival during the mating season through distinctive vocal calls, a new study has revealed.

Male seals compete fiercely for access to females during the breeding season, and their violent, bloody fights take a toll on both winners and losers.

However, these battles are relatively rare.

The study found that the males avoid fights by learning the distinctive vocal calls of their rivals.

When they recognise the call of another male, they know whether to attack or flee depending on the challenger's status in the dominance hierarchy.

Researchers from University of California-Santa Cruz have been studying the behaviour of northern elephant seals at Ano Nuevo State Reserve since the late 1960s.

"Anybody who has studied elephant seals knows that their vocal communications are important, but we haven't known what information is encoded in the vocalisations," said co-lead researcher Caroline Casey.

"What we found is that these calls are identity signals. Each male has a unique call, and they learn to recognise the calls of their competitors, so they know how to respond during contests," Casey explained.

During the breeding season, the beaches at Ano Nuevo are crowded and noisy.

Males establish their social status initially through physical confrontations, but most of the interactions between males consist of ritualised displays involving loud vocalisations called "clap threats", as well as physical posturing.

Sometimes they slam their chests onto the sand to send a seismic signal.

High-ranking "alpha" males defend their harems from all challengers, while mid-ranking "beta" males respond to rivals according to their relative social status.

"There is a very structured social network among the males in a given location. Although the rate of conflict between males is very high, the rate of actual physical aggression is very low - only about five percent," said another lead researcher Colleen Reichmuth.

The study was published in the journal, Royal Society Open Science.