Birds sit on the back of a zebra in the Nairobi National Park, near Nairobi, Kenya, November 21, 2018. (Photo by Baz Ratner/Reuters)

Greyhounds with stuffed and sprung model monkeys strapped to their backs before a hurdle race at Wellinborough. (Photo by E. Bacon). 21st April 1928

Opossums on their mothers back at a game reserve in Central Minnesota, USA, on September 2, 2013. (Photo by Caters News Agency)

A mouse rides on the back of a frog in floodwaters in the northern Indian city Lucknow June 30, 2006. (Photo by Pawan Kumar/Reuters)

Model Bella Hadid celebrates her 20th birthday with her mother Yolanda Foster, The Weeknd and Shanina Shaik at Up & Down in New York City, NY on October 10, 2016. (Photo by TheStewartofNY/Splash News)

A leaflet denouncing South Korean President Park Geun-hye lies on the ground after it was torn at a protest calling Park to step down, in Seoul, South Korea, November 19, 2016. (Photo by Kim Hong-Ji/Reuters)

Lutricia Bock of Germany falls down as she performs during the ladies short program at the ISU European Figure Skating Championship in Bratislava, Slovakia, January 27, 2016. (Photo by David W. Cerny/Reuters)

A girl pours water over a dog to cool it down, in the rebel held besieged town of Douma, eastern Damascus suburb of Ghouta, Syria, June 23, 2016. (Photo by Bassam Khabieh/Reuters)