Ear mites are usually contracted at shows, either from another rabbit when they are on the show table, or by the judge passing them from one rabbit to another as he judges the show.
How do you know if your rabbit has ear mites? Well, you should be performing a quick health check on your rabbits once a week or so. When you check the ears, if you see dry, peeling skin on the inside, it's a pretty good bet that your rabbit has ear mites.
Fortunately, this condition is easily and cheaply treated. All you have to do is get a little coconut or vegetable oil and spread it around the inside of the ears. Do this every day for a week or so.
No more ear mites!