I can tell which of the 5 it is that's barking.

They get a deeper, much throatier bark when they are "serious" as opposed to "open the door I wanna to through."

Drives my Dad nuts, if I'm busy in the kitchen, I'll call out, "Can you get the door, Lacey wants to come in!" He has no clue which one is which, hee heeeeee.

Marlin is the funniest. When he is out and wants in, he gives a "bark BARK!" and waits. You BETTER open that door instantly (of course this doesn't happen ) cuz next he starts the "woe is me whine:" I'm all alone, no one loves me, I've been left out here . . . " And that keeps on until we get to the door.