Desert bighorn sheep is a variation of the bighorn sheep (also called the Canadian sheep), occurring only in desert areas in the south-west of the United States and northern Mexico. The sheep differs from other representatives of the species as it is well-adjusted to the harsh conditions of life in the desert. It is able to survive long periods of drought, and - unlike other mammals - its body temperature can safely fluctuate several degrees, allowing it to survive hot days and cold nights. From the 1960s North America has taken steps to increase the population of this endangered species. In result of these undertakings desert bighorn sheep was restored in the Zion National Park at the end of the 20th century, where the species became extinct in the first half of the century. Thanks to the efforts of conservationists there are more than a thousand sheep in the park.