The llama stands 0.9 to 1.3 m (3 to 4.3 ft) high at the shoulder and is usually white, blotched with black and brown; sometimes it is pure white or pure black. Male llamas have been used as beasts of burden in the Andes Mountains in Peru and Bolivia for more than 4000 years. They can carry as much as 91 kg (200 lb) for 12 hours a day, but they are not ridden. When llamas get tired of working, they lie down and refuse to move, often spitting at their driver! Llamas are also raised as pets and for their wool.