Young goats learn new and distinctive bleating "accents" once they begin to socialise with other kids.
The discovery is a surprise because the sounds most mammals make were thought to be too primitive to allow subtle variations to emerge or be learned. The only known exceptions are humans, bats and cetaceans – although many birds, including songbirds, parrots and hummingbirds have legendary song-learning or mimicry abilities.
Now, goats have joined the club. "It's the first ungulate to show evidence of this," says Alan McElligott of Queen Mary, University of London.
McElligott and his colleague, Elodie Briefer, made the discovery using 23 newborn kids. To reduce the effect of genetics, all were born to the same father, but from several mothers, so the kids were a mixture of full siblings plus their half-brothers and sisters.
The researchers allowed the kids to stay close to their mothers, and recorded their bleats at the age of 1 week. Then, the 23 kids were split randomly into four separate "gangs" ranging from five to seven animals. When all the kids reached 5 weeks, their bleats were recorded again. "We had about 10 to 15 calls per kid to analyse," says McElligott.
Some of the calls are clearly different to the human ear, but the full analysis picked out more subtle variations, based on 23 acoustic parameters. What emerged was that each kid gang had developed its own distinctive patois. "It probably helps with group cohesion," says McElligott.
"People presumed this didn't exist in most mammals, but hopefully now, they'll check it out in others," says McElligott. "It wouldn't surprise me if it's found in other ungulates and mammals."
Erich Jarvis of Duke University Medical Center in Durham, North Carolina, says the results fit with an idea he has developed with colleague Gustavo Arriaga, arguing that vocal learning is a feature of many species.
"I would call this an example of limited vocal learning," says Jarvis. "It involves small modifications to innately specified learning, as opposed to complex vocal learning which would involve imitation of entirely novel sounds."
Journal reference: Animal Behaviour, DOI: 10.1016/j.anbehav.2012.01.020
September 09, 2012
