A Saudi police officer receives emergency calls at a call center, ahead of the Hajj pilgrimage in the Muslim holy city of Mecca, Saudi Arabia, Tuesday, August 6, 2019. The hajj occurs once a year during the Islamic lunar month of Dhul-Hijja, the 12th and final month of the Islamic calendar year. (Photo by Amr Nabil/AP Photo)

A participant takes part in a “Zombie Walk” parade in Kiev, Ukraine on October 27, 2018. (Photo by Gleb Garanich/Reuters)

Aerial view of pond cypress at Qinglongwan Forest Park near Ningguo, China on November 26, 2017. (Photo by Imaginechina/Rex Features/Shutterstock)

Rohingya refugee sisters Nur Kaida (R) and Ruhana hug each other at their shelter at the Palongkhali refugee camp near Cox's Bazar, Bangladesh December 21, 2017. (Photo by Marko Djurica/Reuters)

Respect, Kronotsky nature reserve, Russia. The photographer’s cat, Ryska – her name means little lynx in Russian – stands outside their cabin and with aggressive posturing warns off a fox. In winter, foxes would regularly visit the cabin searching for food. If one peered in at the window, possible when the snow was deep, Ryska would sit on the other side, fur raised, and growl. When outside, she would hold her ground. The foxes were not always frightened and so encounters could be a sort of dance. (Photo by Igor Shpilenok/Unforgettable Behaviour/NHM)

Muhannad al-Kadiri (R),18, and Ibrahim Eid, 16, demonstrate their Parkour skills over a military vehicle in the rebel-held city of Inkhil, west of Deraa, Syria, February 4, 2017. (Photo by Alaa Al-Faqir/Reuters)

A member of the Revolutionary Armed Forces of Colombia (FARC) pose for a picture at a camp in the Colombian mountains on February 2005. (Photo by Frank Piasecki Poulsen)

Catholic pilgrim Matilde Madalena de Jesus crawls on a rocky trail carrying a bottle of water on her head during the annual pilgrimage of the dead (Romaria dos Finados), in the city of Juazeiro do Norte, Ceara state, in Brazil October 31, 2016. (Photo by Ueslei Marcelino/Reuters)