sex. During and after the rut, however, they group together to form larger groups for protection, and to conserve energy. When the rut begins, rams begin to fight for dominance among their flocks; dominant rams then choose their ewes without competition from the losers. Only mature rams (those over 6 years old) fight for dominance. The young will sometimes threaten older males, but never charge them. The mature rams fight by standing next to each other and spinning around, then one steps back and charges. O. a. polii males have been noted to rise up on their hind legs when they clash with opponents, which is not common in lowland sheep and similar to the fighting habits of goats. The males commonly emit grunts while fighting and often chip their horns or break their noses. After dominance has been established, the rams begin to select their ewes. Although Marco Polo sheep rams are known to herd females, during the rut males pair off with females to reproduce. Males will approach a flock of females and smell the urine of possible mates. When smelling the ewe's urine, the males display the Flehmen response to test if the ewe is in estrus. Shackleton calls this phenomenon "lip-curl" and describes it as "raising the head with the mouth open and upper lip curled back." The ram then splits from the flock to copulate with his ewe and afterward will often stay with the flock for a month or two. Conservation Hunting Hunting the Marco Polo sheep first became popular when Mohammed Zahir Shah, king of Afghanistan, hunted and killed a ram in the 1950s. He thereafter declared that the valley in which he hunted be a protected habitat for the sheep as a hunting grounds for Afghan royalty, and it was not until 1968 that an American tourist was allowed to hunt in the reserve. In 2008, it was estimated that American hunters paid an average of $20,000 to $25,000 for an expedition to hunt a Marco Polo sheep. A recent study put the cost at $40,000 per permit. In 1976, in Khunzerav, the sheep's population was estimated to be 300. This number declined to a maximum of 160 between 1978 and 1981, and declined again to only 45 in 1991. George Schaller of the Wildlife Conservation Society estimated the worldwide population in 2003 as around 10,000, half what Ronald Petocz estimated in