A giant panda cub is pictured in an incubator at the Ya'an Bifengxia Giant Panda Breeding and Research Center in Ya'an city, southwest China's Sichuan province, 21 August 2015. Ten tiny panda cubs made their first public appearance at China's Ya'an Bifengxia Giant Panda Breeding and Research Center in southwestern Sichuan province on Friday (21 August 2015). All of the ten giant pandas were born in 2015. The oldest of them is just two month old, while the youngest one was born a week ago. This marks the first time they were put together as a group since they were born. (Photo by Imaginechina/Splash News)

Two De Brazza's monkeys stand together at Port Lympne Wild Animal Park on June 21, 2011 in Hythe, England. Port Lympne has welcomed a host of new arrivals this year with wildebeest, colobus monkeys, gorillas and rhinos all adding to the current stock. Port Lympne and Howletts Wild Animal parks were set up by the late John Aspinall to protect and breed rare and endangered species and, where possible, return them to safe areas in the wild. The Aspinall Foundation which runs the parks also manages two gorilla rescue and rehabilitation projects in the central African countries of Gabon and Congo where they have successfully reintroduced over 50 gorillas to the wild. (Photo by Dan Kitwood/Getty Images)

Space shuttle Discovery sits atop NASA's 747 Shuttle Carrier Aircraft (SCA) ready to transport it from Kennedy Space Center to the Washington D.C., on April 17, 2012 in Cape Canaveral, Florida. Following the retirement of the shuttle fleet, Discovery will fly to Washington for display at the Smithsonian's National Air and Space Museum. (Photo by Lofty Ambitions)

Zombie enthiusiasts gather near the broadcast tower at Alexanderplatz before setting out on a “Zombie Walk” in the city center on October 27, 2012 in Berlin, Germany. Approximately 150 zombies, who had organized themselves through Facebook, walked and limped across Alexanderplatz, growled and moaned at passersby and performed their jerking dances. (Photo by Sean Gallup)

Alluvial Fan, China. A vast alluvial fan blossoms across the desolate landscape between the Kunlun and Altun mountain ranges that form the southern border of the Taklimakan Desert in China’s XinJiang Province. Image taken by the ASTER instrument on NASA’s Terra satellite on May 2nd, 2002. (Photo by NASA/GSFC/USGS EROS Data Center)

Children react after what activists said was shelling by forces loyal to Syria's President Bashar al-Assad near the Syrian Arab Red Crescent center in the Douma neighborhood of Damascus May 6, 2015. (Photo by Bassam Khabieh/Reuters)

A 6-month old female giant panda cub, an offspring of Xing Xing, formerly known as Fu Wa and Liang Liang, formerly known as Feng Yi, plays at the Giant Panda Conservation Center at the National Zoo in Kuala Lumpur, Malaysia, Thursday, February 18, 2016. (Photo by Joshua Paul/AP Photo)

Vigilantes armed with automatic rifles patrol the streets of Bujumbura, a city plagued by killings and violence as Burundi's crisis deepens. Here: an armed vigilante holds an AK-47 rifle in the center Bujumbura, Burundi, November 20, 2015. (Photo by Goran Tomasevic/Reuters)