“Hippo Chase”. As we approached the camp the Selinda Reserve of northern Botswana our boat passed by a hippo resting in the water. I turned around to look back at the boat's wake and saw the hippo charging after us! The hippo must've been tired from an all-nighter because he was angry. He rose way up out of the water three times trying to chase our boat! He was coming at us with such force that he created a wake of his own. Photo location: Selinda Reserve of northern Botswana. (Photo and caption by Curtis Simmons/National Geographic Photo Contest)

In this Friday, February 6, 2015 photo, sandhill cranes begin to stir after resting for the night at a roosting location along their winter migration route in Cecilia, Ky. According to counts made by biologists with the Kentucky Fish and Wildlife Resources, about 12,000 of the birds have stopped in Cecilia this week during their winter northward migration on their way to their nesting grounds in the Great Lakes region. (Photo by David Stephenson/AP Photo)

A policewoman reacts as she falls off from a motorcycle while taking part in a rehearsal for Independence Day celebrations, in Ahmedabad, India August 4, 2017. (Photo by Amit Dave/Reuters)

Revellers attend the 25th edition of the Sziget Festival on August 9, 2017 in Budapest, Hungary. The Sziget Festival, one of the largest music and cultural festivals in Europe, celebrates its 25th anniversary in 2017, taking place from August 9-16 on the Hajogyari Sziget in Budapest. (Photo by Laszlo Mudra/Rockstar Photographers)

In this Wednesday, April 12, 2017, photo, waitresses wait outside a restaurant in Pyongyang, North Korea. A generational divide is quietly growing in North Korea, often hidden behind relentless propaganda. On the streets there are young women in not-quite mini-skirts and teenage boys with baseball hats cocked sideways, K-pop style. (Photo by Wong Maye-E/AP Photo)

Robot pianist Teo Tronico performs at the World Robot Conference (WRC) 2017 at Etrong International Exhibition & Convention Center on August 22, 2017 in Beijing, China. The World Robot Conference 2017 is held from August 23 to 27 in Beijing. (Photo by Liu Guanguan/China News Service/VCG via Getty Images)

Debutantes Amira Rayner, 19 (L) and Eliza Lewis, 17 (R) prepare at Boughton Monchelsea Place ahead of the Queen Charlotte's Ball on September 9, 2017 in Maidstone, England. (Photo by Jack Taylor/Getty Images)

Indian Air Force personnel parade during the 85th Air Force Day celebrations at Hindon Air Force base in Ghaziabad on October 8, 2017. (Photo by AFP Photo/Stringer)