During the First and Second World Wars, Rottweilers saw service in various roles, including as messenger, ambulance, draught, and guard dogs. Rottweilers living in hot climates may have acclimatised and may be missing the undercoat. Rottweiler coats tend to be low maintenance, although they experience heavy shedding before their seasons (females) or seasonally (males). According to American Kennel Club breed standards, a Rottweiler's coat is short and straight. A coat that is long or wavy is considered a flaw to the AKC. A coat that is long or wavy is considered a flaw to the AKC. The color and markings of a Rottweiler are very distinctive.