Turkana tribesmen walk with guns in order to protect their cattle from rival Pokot and Sambur tribesmen near Baragoy, Kenya February 14, 2017. Cattle rustling and competition for grazing have long troubled northern Kenya, but severe drought and political rivalries ahead of the elections have exacerbated the situation between ethnic tribes. (Photo by Goran Tomasevic/Reuters)

Tamberly Conway, bottom left, takes part in a large snowball fight in Dupont Circle on Sunday January 24, 2016 in Washington, DC. The Washington, DC area was blanketed by a large snow event. (Photo by Matt McClain/The Washington Post)

Hadeel, 10, asks a passerby for help to pay a medical bill as her father Shahrour, 54, sits in his wheelchair in the Douma neighbourhood of Damascus Syria February 3, 2016. Shahrour said he developed diabetes at the beginning of the war in Syria. A lack of insulin led to his medical condition worsening and his right foot had to be amputated. Recently he also suffered a stroke that paralysed half his face. He and part of his extended family, a total of 18 people, live together and struggle to get by. (Photo by Bassam Khabieh/Reuters)

Rihanna and Drake perform at the BRIT Awards at the O2 arena in London, Britain, February 24, 2016. (Photo by Stefan Wermuth/Reuters)

A picture made available on 13 May 2016 shows A Tiwa girl performing her traditional dance as they celebrated the Wanchuwa festival in Karbi Anglong District of Assam state, India, 11 May 2016. Wanchuwa is one of the most important festivals of the Tiwa tribal community living in the hills as it is related with agriculture which is the mainstay of their economy. Tiwas pray for a bountiful harvest during this festival and to protect their crops from pest and other natural calamities. Tiwa is a major tribe of Assam state who practice Jhum or shifting cultivation for their living in the hills. (Photo by EPA/Stringer)

Mongolian President Tsakhiagiin Elbegdorj (C) walks towards the media after casting his vote for the parliamentary elections at a polling station in Ulaanbaatar, Mongolia, June 29, 2016. (Photo by Jason Lee/Reuters)

Devil Ark manager Dean Reid reacts as Tasmanian Devil joeys climb on him before the first shipment of healthy and genetically diverse devils to the island state of Tasmania leave the Devil Ark sanctuary in Barrington Tops on Australia's mainland, November 17, 2015. The largest group so far of disease-free Tasmanian devils has been released in the wild, as part of plans to save the carnivorous marsupials from a cancer threatening them with extinction. (Photo by Jason Reed/Reuters)

Pakistani street performers sit around fire waiting for customers on a chilly evening in Rawalpindi, Pakistan, Wednesday, November 11, 2015. Some parts of Pakistan are facing a harsh winter. (Photo by B. K. Bangash/AP Photo)