There is only one species of true wild horse left in the world. In past centuries, Przewalski's horses roamed freely in Siberia, Mongolia, and China, keeping their distance from humans. The wild horse was discovered by Russian geographer Nikolai Przewalski in 1878, but by the late 1960s, this species had almost disappeared. The cause was the extremely harsh winters of 1944-1945, which led to a significant reduction in the population. All modern Przewalski's horses are descended from the wild horses that remained at that time in zoos and reserves around the world. The wild horse differs from the domesticated horse in the number of chromosomes. Domesticated horses have 64 chromosomes, while wild horses have 66. Therefore, modern scientists believe that there were once several species of horses, and wild and domesticated horses had different ancestors. Visually, these horses also differ: Przewalski's horse has a donkey-like tail, small ears, legs covered with dark stripes like a zebra, and a dark stripe running from the withers to the tail. Nonetheless, wild and domesticated horses can produce offspring together. Przewalski's horse is listed in the Red Book of Russia and the Red List of the International Union for Conservation of Nature. The population is being restored in several countries around the world. In Russia, it has been reintroduced in the Orenburg Reserve since 2015. In the Orenburg steppes, they produced their first offspring by 2018. Now the local population numbers about 100 horses. In the wild, horses live in herds led by an alpha male, with the others being his "harem" and foals. In the reserve, they are under constant observation by scientists.