A miner with a donkey makes his way through the low and narrow tunnel leading out of a coal mine in Choa Saidan Shah in Punjab province, April 29, 2014. Workers at this mine in Choa Saidan Shah dig coal with pick axes, break it up and load it onto donkeys to be transported to the surface. Employed by private contractors, a team of four workers can dig about a ton of coal a day, for which they earn around $10 to be split between them. The coalmine is in the heart of Punjab, Pakistan's most populous and richest province, but the labourers mostly come from the poorer neighbouring region of Khyber Pakhtunkhwa. (Photo by Sara Farid/Reuters)

A walruses at Hagenbeck Zoo in Hamburg, Germany on July, 7, 2015. (Photo by Werner Struss/Startraks action)

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 monkey jumps from a branch at Yangon Zoological Gardens in Yangon, Myanmar, 06 April 2016. Yangon Zoological Gardens (Yangon Zoo) is the oldest and second largest zoo in Myanmar. (Photo by Lynn Bo Bo/EPA)

A man poses with a hyena along a street in Lagos, Nigeria November 4, 2008. (Photo by Akintunde Akinleye/Reuters)

Young men play basketball on an improvised court wedged between a construction site and the shells of once grand colonial homes in Havana, July 20, 2015. As much as the young in Cuba welcome political opening and economic reform, such changes are unlikely to filter down to their lives anytime soon. (Photo by Meridith Kohut/The New York Times)

Meet the star students of orangutan school – the unique rehab centre where orphaned apes are taught how to climb trees and survive in the wild without their mum and dad. (Photo by Caters News)

Drivers push cars to gas station during “oil crisis”, Roslindale, Boston, Massachusetts, 1973. (Photo by Spencer Grant/Getty Images)