Most German Shepherds have a double coat, meaning that they have an outer coat layered with a thicker undercoat. The length of this coat is most commonly medium, but a long coated variety exists. However, the long coated variety only has a single outer coat, and lacks the thicker undercoat. The long coat gene is recessive, meaning that it must be passed on from both parents in order for a long coat to occur. This makes long coated German Shepherds considerably more rare than those with medium length coats.
Von Stephanitz, the German Shepherd breeder who developed and standardized the breed in the 1800s, discouraged against the long-coated variety. The lack of undercoat makes the dogs less resistant to weather, and also makes the coat lack the waterproofing that an undercoat provides. Long coat German Shepherds should still be able to perform as a protection dog or a guard dog, but only if they are in a suitable climate and will not be expected to swim through icy water or be kept outdoors in frigid winter conditions. Unfortunately, the recessive quality of the long coat gene means that many long coated German Shepherds are bred from a limited gene pool in order to maintain this trait. Their limited gene pool, as well as the fact that they are being bred for the appearance of their coat over working ability, means that many long coated German Shepherds may not have the appropriate temperament required for true protection work. However, this is not true of all long coat German Shepherds. Dogs should be judged on their working ability on an individual basis, and you cannot assume that a long coat will always represent an inferior dog.