Pit bull owners crop the ears of the dog to limit the areas that other dogs can grab when fighting and to make it harder for other dogs to read the mood of the pit bull. This practice is usually seen in dog fighting. Dog owners may also do this just to alter the appearance of the dog.
While there is some legitimate use of ear cropping in some breeds, the American Veterinary Medical Association notes that there is long-standing opposition to the cropping of ears just for the sake of altering appearance. The organization cites that as far back as 1895, the American Society for the Prevention of Cruelty to Animals requested the American Kennel Club to remove cropped ears from breed standards.