Children hold signs thanking truck drivers hauling rocks to the Lake Oroville Dam after an evacuation was ordered for communities downstream from the dam in Oroville, California, U.S. February 13, 2017. (Photo by Jim Urquhart/Reuters)

A baby elephant eats in a swamp in Amboseli national park, Kenya, March 19, 2017. (Photo by Goran Tomasevic/Reuters)

Medic James E. Callahan of Pittsfield, Mass., gives mouth-to-mouth resuscitation to a dying soldier in war zone D, about 50 miles northeast of Saigon, June 17, 1967. Thirty-one men of the 1st Infantry Division were reported killed in the guerrilla ambush, with more than 100 wounded. (Photo by Henri Huet/AP Photo)

A man sits next to a damaged idol of Hindu goddess Kali which was taken out after its immersion in the river Ganges in Haridwar, India, March 29, 2017. (Photo by Danish Siddiqui/Reuters)

A vendor prepares paan, a betel nut-based chewable stimulant at a flower market in Kolkata, India, January 18, 2016. (Photo by Rupak De Chowdhuri/Reuters)

Villagers offer flowers to a wild tusker, laying dead in a field in Panbari villagein Panbari village on the outskirts of Gauhati, India, Thursday, November 2, 2017. According to a veterinarian the tusker died of food poisoning. Scarcity of food and illegal encroachment of forest areas have forced these wild elephant to move to populated areas for food. (Photo by Anupam Nath/AP Photo)

Tactics reminiscent of the early American frontier days are now being used in Vietnam. Lieutenant Commander Donald D. Sheppard, UBN, of Coronado, California, aims a flaming arrow at a bamboo hut concealing a fortified Viet Cong bunker on the banks of the Bassac River, Vietnam on December 8, 1967. (Photo by AP Photo)

Revellers out and about in Newcastle, England on “Black Eye Friday” or “Mad Friday” on December 22, 2017 as people across the country celebrate the start of the Christmas break by hitting bars, pubs and clubs. This partygoer had so much fun she looks lost. (Photo by Craig Connor/North News and Pictures)