Puppies and adult dogs alike can often be found nibbling on each other's ears to show affection or submission. They also might be grooming each other to prevent ear mites, or snacking on each other's ear wax.
Dogs are social creatures that rely on body language to communicate. Because of this, chewing on each other's ears has a wide variety of meanings. Dogs most commonly chew and lick ears in order to convey affection and invite each other to play. Lacking opposable thumbs, dogs often use their mouths and teeth to get each other's attention and grab other dogs for fun.
Dogs interact with the world through their mouths. Puppies in particular use their mouths to investigate objects, including other dogs. Ears are an easy target not likely to incite aggression. However, sometimes an overenthusiastic tongue can penetrate too deeply in the ear canal and cause an ear infection, so dogs' ears should be examined regularly for brown discharge or an unusual odor.
Dogs are attracted to strange smells and tastes, as well as the saltiness of the ear's lining. Dogs who chew other dogs' ears may simply be enjoying the taste. However, some trainers categorize ear biting as another form of mouthing, and recommend training puppies out of this behavior.