drastic seasonal change. The Marco Polo sheep's face is lighter colored than the body. Most argali have a round tail approximately long, ending in a tuft of hair; O. a. polii's tail is a little bit longer: around . Mature rams on average weigh . At the withers, rams grow to approximately in height and ewes to . The sheep rut in December. Gestation lasts about 160 days, with single births being normal and twins uncommon. A captive ewe once gave birth to five lambs at once, then triplets two years later. Marco Polo sheep have an average life span of 13 years. The horns develop rings each year by which the age of male animals may be determined. Since females do not have horns, it is harder to determine their age. No data have been compiled showing the susceptibility of the sheep to disease, although tests have been run on similar species of sheep and the data may be similar. Since Marco Polo sheep are reluctant to approach people, it is not likely that they can catch diseases common to domestic flocks, although some domestic sheep are allowed to run wild over the mountains, and it is unknown if they come into contact with Marco Polo sheep. However, the shepherds in the area do not generally have access to veterinary care for their animals, and it is possible that these could transmit diseases to the wild sheep. Habitat Most Marco Polo sheep live in the Pamir Mountains region adjacent to the borders of Afghanistan, Pakistan, Kyrgyzstan, Tajikistan and China. Their elevation ranges from above sea level. The subspecies lives mainly in the northwestern part of the Hunza district of Pakistan along the Chinese border, inhabiting the Kilik Mintaka border and the northwestern area of Khunjerab National Park. Marco Polo sheep also inhabit the Wakhan Corridor, along the Afghanistan border. They share much of their habitat with animals such as the Siberian ibex. During summer, Marco Polo sheep prefer to be near riparian areas and vegetation, while during winter they prefer to be in gentler and south-facing mountain slopes. Terrain ruggedness and annual mean temperature are the two major factors that affect their distribution. Behavior Marco Polo sheep are similar in behavior to other members of the genus Ovis. They generally live in small flocks of a few dozen. During the summer, they break into smaller flocks of the same