What do we mean by 'accents' in animals?

Cod
Image caption Cod vocalise by vibrating their swim bladder

When we think about accents in humans, we know typically they will be a clue to where people live and grew up.

To someone familiar with the accents of England, it's easy to tell the difference between someone who comes from Essex and someone who comes from Newcastle.

There have been a lot of reports about cod having an "accent".

When we talk about the "accents" animals make, scientists usually use the term "vocal learning" instead.

"It means you're listening to the other members of your species surrounding you and you can produce some vocalisations," says Dr Alan McElligott, of Queen Mary University of London.

Goat

He specialises in animal behaviour and has studied vocal learning in goat kids.

"Nobody expected to find some evidence of vocal learning in goats, but we did," he says.

"They begin to sound more similar depending on the social group in which they were raised."

There are some other mammals, such as elephants, bats and dolphins, which can do it but Dr McElligott says this is quite "rare".

"Vocal learning is very common in song birds," he explains.

Elephant

What all of these animals have in common is the importance they place on vocalisation.

So - back to the cod. What could be going on there?

"Every individual cod, like every individual human, has a unique genome," says Dr McElligott.

"Slight differences in their genetics affect their size, their shape and their sound because sounds are usually linked to the size and shape of the animal.

"You can have regional differences in the sound that animals are producing within a species and it could be completely genetically determined."

Fishing boat surrounded by birds

Dr Steve Simpson, from Exeter University, carried out the research on the fish.

"Cod particularly have very elaborate calls compared with many fish," the University of Exeter professor told BBC News.

"They vibrate their swim bladder - their balloon inside them - to make sound.

"They can create a whole range of different pops, grunts and rumblings."

He says these different sounds could be influenced by a variety of factors, including genetics, the environment around them and vocal learning.

These calls are what help them find mates.

And one of the biggest issues they face is that noise pollution in the seas could stop them from meeting each other - and therefore breeding.

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