Small ears help to reduce the risk of frostbite, and thick fur that grows on the paws protects the dogs from sharp ice. Many spitz breeds, like the Akita and Chow Chow, retain wolf-like characteristics like independence, suspiciousness, and aggression towards unfamiliar humans and other dogs, and they require much training and socialization when they are puppies before they become manageable in an urban environment. Some, such as the Karelian Bear Dog, are more difficult to train as companion dogs. Some sources claim spitzes are more prone to rabies than other dog types. Some breeds, such as the Pomeranian, have manes. Spitzes, with their thick fur, fluffy ruffs, curled tails and small muzzles and ears, have been bred into non-working dogs designed to be companions or lap dogs. This trend is most evident in the tiny Pomeranian, which was originally a much larger dog closer to the size of a Keeshond before being bred down to make an acceptable court animal. The Keeshond, the Wolfspitz variation of the German Spitz, is an affectionate, loyal, and very energetic pet that was bred as a watch-dog for barges (hence the name Dutch Barge Dog). Often, these breeds are recognized for their "smiling" mouths. Other spitzes that have been bred away from working uses are the American Eskimo Dog, Alaskan Klee Kai, German Spitz, Volpino Italiano and Japanese Spitz. This list might not be complete. The dogs listed here might be classified as toy dogs, herding dogs, sled dogs, and in other types. Modern tango  Modern tango music (or contemporary tango) includes several different types of tango. It includes  Nuevo tango, the music of Astor Piazzolla, Osvaldo Pugliese, Horacio Salgán and others. They are the composers who altered the idea of tango, during and after the 1950s. Neotango, sometimes referred to as electortango, it is the tango revival music from the 1990s and early 21st Century that renewed an interest in tango music and dancing. It is includes bands, such as Gotan Project, Bajofondo, Otros Aires, Narcotango and others. Contemporary Acoustic Tango, this is not really a genre. But, there are contemporary acoustic tango groups with original compositions and orchestration, such as Juan Carlos Cáceres, Hugo Diaz, Ruben Rada, etc.