Gelada baboons (Theropithecus gelada) play in their enclosure at the Zoo in Zurich, Switzerland, Wednesday, May 15, 2013. (Photo by Steffen Schmidt/Keystone/AP Photo)

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 masked Burundian protester faces soldiers in front of a burning barricade during an anti-government demonstration against President Pierre Nkurunziza's bid for a third term in the capital Bujumbura, Burundi, 25 May 2015. Street protests continued on 25 May as the United Nations Secretary-General Ban Ki-moon condemned the killing of the leader of the oppsition party Union for Peace and Development (UPD) Zedi Feruzi who opposed Nkurunziza's bid. (Photo by Dai Kurokawa/EPA)

The moon rises over people gathered on Glastonbury Tor ahead of tomorrow's Blue Moon on July 30, 2015 in Somerset, England. The full moon appearing on July 31 will be what's called a Blue Moon, which refers to the second of two full moons appearing in the same calendar month. The last time this happened was in 2012 and there isn't due another until 2018. (Photo by Matt Cardy/Getty Images)

Four-month-old fox cubs squaring up to each other in Walthamstow, England on August 7, 2015. (Photo by Greg Morgan/Barcroft Media)

Victor Peralta from Uruguay gestures during the fourth International Tattoo Convention in Quito, September 25, 2016. (Photo by Kevin Granja/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)

A member of Sakura circus team performs during the second day of a one week show in Padukka, near Colombo, Sri Lanka November 28, 2016. (Photo by Dinuka Liyanawatte/Reuters)