Selachimorpha

[[number]]

when we say:

"Sharks hug with their mouth"

aren't we saying that all sharks share one mouth and they hug with it?

shouldn't we say instead:

"Sharks hug with their mouths"?

so now this means that each shark hugs with his own mouth?

[Rover_KE]

Yes - mouths is correct.

Rover

[Raymott]

when we say:

"Sharks hug with their mouth"

aren't we saying that all sharks share one mouth and they hug with it?

shouldn't we say instead:

"Sharks hug with their mouths"?

so now this means that each shark hugs with his own mouth?

By the same token, "Sharks hug with their mouths" could imply that sharks have more than one mouth."
I don't have a problem with the original sentence.

[Barb_D]

I agree with Ray. There's no set answer to this in English.

Usually context makes things make sense. You usually know that it will mean that each person (or shark) had or used only one of something from what you know about the world.

Sometimes there is ambiguity: The girls brought their favorite dolls. If it's really important that you know that each girl had only one doll, you would have to rewrite.