Gerbils and hamsters are both rodents and are fascinating animals. Gerbils are between 6 and 12 inches long, including their tail, which can be one-half of their total length. The most common type of gerbil kept as a pet is the Mongolian. Hamsters belong to the subfamily Cricetinae. The most common hamster for pets are the 6 inch Syrian, also known as the Golden Hamster or Teddy Bear Hamster. Unlike Gerbils, Hamsters are virtually tailless.