Bull riders prepare prior to a bull riding event in Santa Tecla, El Salvador, December 15, 2016. (Photo by Jose Cabezas/Reuters)

Women pose for a picture at the entrance of the Carlton Hotel, in the government controlled area of Aleppo, Syria December 17, 2016. (Photo by Omar Sanadiki/Reuters)

A giant panda cub falls from the stage while 23 giant pandas born in 2016 seen on a display at the Chengdu Research Base of Giant Panda Breeding in Chengdu, Sichuan province, China, September 29, 2016. (Photo by Rex Features)

Cars drive under a rainbow near Bad Langensalza, Germany, Wednesday, November 2, 2016. (Photo by Jens Meyer/AP Photo)

A woman walks with a squirrel on her shoulder at Maeklong market at the outskirts of Bangkok, Thailand September 20, 2016. (Photo by Jorge Silva/Reuters)

A young Shiite Muslim child participates in a Muharram procession in Ahmadabad, India, Sunday, October 9, 2016. (Photo by Ajit Solanki/AP Photo)

A group of fashionable nonagenarians pose for a photo in Pengzhou, Sichuan, China on October 12, 2016. (Photo by Rex Features/Shutterstock)

A flock of starlings flies over Lake Leman on an autumn morning in the Lavaux near Grandvaux, Switzerland October 20, 2016. (Photo by Denis Balibouse/Reuters)