White lioness Azira lies in the cage with her three white cubs, on February 4, 2014. Zoo owner Andrzej Pabich says white lions often have defects that prevent giving birth, or the mother rejects her cubs, but Azira has been patiently feeding and caring for her little ones. (Photo by Czarek Sokolowski/Associated Press)

A young oriental small-clawed otter at the zoo in Neumuenster, Germany, March 5, 2014. The six young otters (one male, five female) were born on December 7, 2013. (Photo by Maja Hitij/EPA)

A tourist poses for a picture with the Sphinx at the Pyramids of Giza in Cairo, Egypt, on October 19, 2011. (Reuters/Jamal Saidi)

Participants wear traditional clogs as shepherds lead their sheep through the center of Madrid, October 28, 2012. (Photo by Andres Kudacki/Associated Press)

Winner of the Sandow bodybuilding competition, Mr. Murray. (Photo by Reinhold Thiele/Thiele/Getty Images). Circa 1905

Two elderly men smoking pipes of opium on a terrace in Korea. (Photo by Bert Hardy/Picture Post/Getty Images). August 1950

In this May 14, 2016 photo, children wearing their school backpacks climb on a cliff using a bamboo ladder on their way home from school in Zhaojue county, southwest China's Sichuan province. A village in China's mountainous west where schoolchildren must climb an 800-meter (2,625-foot)-high bamboo ladder secured to a sheer cliff face may get a set of steel stairs to improve it's safety. (Photo by Chinatopix via AP Photo)