An Amur tiger walks across a passageway after a news conference at the Philadelphia Zoo, Wednesday, May 7, 2014, in Philadelphia. The see-through mesh pathway called Big Cat Crossing is part of a national trend called animal rotation that zoos use to enrich the experience of both creatures and guests. (Photo by Matt Slocum/AP Photo)

A helicopter of the Food and Agriculture Organization of the United Nations (FAO) flies through millions of Locusts as spreads pesticide to fight against a swarm of locusts threatening to reach Amparihibe village on May 7, 2014 in Tsiroanomandidy, Madagascar. FAO mission is to fight the locust's swarm with an insecticide. (Photo by AFP Photo/RIJASOLO)

A woman holds a placard that reads, “I am Charlie”, during a vigil to pay tribute to the victims of a shooting by gunmen at the offices of weekly satirical magazine Charlie Hebdo in Paris, at Trafalgar Square in London January 7, 2015. (Photo by Stefan Wermuth/Reuters)

A reveller parades on stage at the annual Trinidad and Tobago Red Cross Society's Children's Carnival Competition at the Queen's Park Savannah in Port-Of-Spain February 7, 2015. (Photo by Andrea De Silva/Reuters)

A combination of four pictures shows participants dressed in superhero and heroic fantasy costumes posing during the second edition of the Hero Festival in Marseille, France, November 7, 2015. The festival is dedicated to American superhero comics, Japanese mangas, heroic fantasy characters and video games universes. (Photo by Jean-Paul Pelissier/Reuters)

J.S. Burgers Cafe chef Yasuhito Fukui prepares Mr. and Mrs. Burger featuring the U.S. presidential candidates Hillary Clinton and Donald Trump at the hamburger joint in Tokyo, Japan October 7, 2016. (Photo by Megumi Lim/Reuters)

The ruins of a castle stand above the town of Rocca Calascio, close to Santo Stefano di Sessanio in the province of L'Aquila in Abruzzo, inside the national park of the Gran Sasso e Monti della Laga, Italy, September 7, 2016. (Photo by Siegfried Modola/Reuters)

An Afghan man is carried out of a hospital after receiving treatment following a suicide truck bomb attack in Kabul, Afghanistan August 7, 2015. The bombings were the first in Kabul since Mullah Akhtar Mansour took charge of the Taliban last week, and followed a rare truck bomb attack in an eastern province on Thursday. (Photo by Omar Sobhani/Reuters)