Desert bighorn sheep establish two desert areas in southwestern Arizona to help preserve the desert bighorn sheep: Cabeza Prieta National Wildlife Refuge and the Kofa National Wildlife Refuge. In 1941, the San Andres National Wildlife Refuge in New Mexico was added. Desert bighorn sheep populations have trended upward since the 1960s when their population was estimated at 6,700-8,100. The upward trend was caused by conservation measures, including habitat preservation. In 1980, desert bighorn sheep populations were estimated at 8,415-9,040. A state-by-state survey was conducted a few years later and estimated the overall US desert bighorn sheep population at 15,980. The 1993 estimate of
Libyan Desert Desert". The term "Western Desert" contrasts with the Eastern Desert to the east of the Nile River, which lies between the Nile and the Red Sea. The Libyan desert is said to be one of the least hospitable regions on Earth. Its climate is surprisingly variable, being hot in summer, with average daytime temperatures of and above, though this drops rapidly at night. In winter, days are cool, with temperatures averaging , but at night this can drop below freezing, with temperatures of recorded. At these times the formation of hoar frost is not uncommon, and are known as "White