Your canine family member has no way of communicating with you, other than by making noises and using his body language. You already know that his relaxed swaying tail signals that he is happy, while a droopy dragging tail can mean he is scared or on alert. His ears are just as useful for letting you know what's going on inside of his canine brain. Pinning back just one ear is a perfectly normal part of listening and communication in most cases, although it could be a sign of a health problem.
While you may typically see Chester's ears both going in the same direction to listen -- both going forward or both spiked back to catch sounds behind him -- this isn't always the case. Dogs can move their ears completely independent of one another. So your furry pal may be looking at you square in the eyes with his ears completely forward, letting you know that you have his full attention. But then he hears the cat meow or a car drive by and without flinching, moves one ear back to catch a peep of that other sound. Think of the single ear movement as multi-listening.
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The further back your canine's ears go, the more frightful and scared he's feeling. Depending on the situation, he could leave that one ear pinned back and the other one slightly relaxed as he's listening for your voice, for example. Typically when your dog is feeling uneasy, he'll also stick his tail between his legs and crouch down as he walks. These additional cues let you know that you need to get your dog out of that situation quickly, before he has an aggressive outbreak and snaps at another dog.
When your dog is fully confident, his ears will be in a relaxed position. Every pooch's relaxed state is different though. For Chester, relaxed could be one ear up and one ear flopped backwards. If this is a normal comfortable state for him, he'll also stand tall, keep his tail relaxed and may even raise an eyebrow or two. He's just signaling to everyone around that he's perfectly happy -- feel free to pet him.
Your barking buddy could be pinning an ear back because it's bothering him. Ear mites are microscopic parasites that live off of the gunk in your pooch's ears. They cause inflammation, infections and major discomfort for your pup. If you see him shaking his head and rubbing his ear frequently, check both his ears for signs of mites. You might not be able to see them, but if they're prevalent, you'll notice something that looks like coffee grinds in his ears. Just to be on the safe side, take little Chester in for an exam and let your vet know about his new behavior.