The physical attributes of any dog breed have been developed over centuries to make the dog suitable to its environment and to its job. This is why dogs from hot climates, such as the Saluki from Africa or the Chihuahua from Mexico, have short coats and dogs from cold climates such as Huskies and Spitz breeds have thicker, double coats. Dogs used for outdoor work often have double coats too, to protect them during winter.
Northern breeds, also known as Spitz breeds, share many physical attributes. They are typically light in colour, weather-hardy, physically strong and bear a strong resemblance to the wolf. The majority of dogs from this class have double coats. These double coats would have protected the Northern breeds, such as the Siberian husky, Finnish spitz, Alaskan malamute and Pomeranian from the harsh cold. Northern breeds that live in warmer climates tend to shed heavily as a result of not requiring such protection.
Regardless of local climate, a double coat is good protection for any water-going dog. The Leonberger, Newfoundland, and Chesapeake Bay retriever are three popular examples of water dogs that sport a double coat. Water breeds typically have slightly oilier fur than non-water breeds, which acts as further protection against the water. Not all water dogs have double coats though. Poodles and Portuguese water dogs have dense, tightly curled single coats.
Dogs that were bred to guard livestock would have been required to spend a lot of time outside. In the north of Europe especially, this meant that a warm double coat was beneficial to such dogs. The Bergamasco has a distinctive double coat, the top layer of which is corded. The Komondor has a similar coat. The Bouvier des Flandres has a thick double coat that protects him from all weather and even as far south as Australia, herding breeds like the Australian shepherd have evolved their own weather protection.
Grooming double-coated dogs
Double coats require plenty of grooming to stop them matting. The undercoat is soft and downy and functions as a layer of insulation. It can easily become untidy and once matted, it is painful for the dog to heave it combed. The top coat is made up of guard hairs, which repel dirt and water. Regular combing is required to keep it clean. Many owners, especially those living in hot climates, prefer to shave the undercoat during summer to keep their dog from getting too hot.