There are many types of domestic guinea pigs, most breeds recognizable by their hair type. English and American breeds have smooth short hair, Angoras have smooth long hair, and Peruvians have rough long hair. Varieties of breeds are typically distinguished by hair colors and markings. Domestic guinea pigs are still an important source of meat for some people in the Andes. The small animals are also used in a multitude of research roles including biochemical, physiological and pharmacological. In western culture, guinea pigs are regarded as docile, loveable pets. They can't be taught to roll over and fetch, but they'll lie in someone's lap for hours. A full-grown guinea pig is about 6 to 10 inches long, weighs 2 to 4 pounds, and may live for as many as 8 years.