Participants climb over a wall at the “Tough Mudder” endurance event series in Arnsberg September 6, 2014. Competitors who took part in the endurance event saw themselves having to overcome various military style obstacles. (Photo by Ina Fassbender/Reuters)

Participants adjust their make up backstage during a breast model contest in Hefei, Anhui province September 24, 2014. Over 100 models participated in this contest, which was held by a cosmetic company. The winner was awarded 680,000 yuan ($110,825) as cosmetic funds and 30,000 yuan ($4,890) in cash, local media reported. (Photo by Reuters/Stringer)

In this undated photo made available by journal Nature on January 15, 2014, a northern bald ibis (Geronticus eremita) flies in Tuscany, Italy. A new study released Wednesday, January 15, 2014 says the birds choreograph the flapping of their wings, getting a boost from an updraft of air in the wake of the flapping wings by flying behind the first bird and off to the side. When a flock of birds take advantage of these aerodynamics, they form a V. (Photo by Markus Unsöld/AP Photo)

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)

In this photograph taken on July 10, 2012, a Pakistani worker pulls on a wire he will connect to a thick chain that will in turn be used to peel away a slab of the outer structure of a beached vessel in one of the 127 ship-breaking plots in Geddani, some 40Kms west of Karachi. (Photo by Roberto Schmidt/AFP Photo)

A giant river otter, the world's largest otter species, looks out of its enclosure at the newly completed River Safari in Singapore, on March 25, 2013. (Photo by Wong Maye-E/Associated Press)

A wolf skin is on display for sale next to a painting of Russian communist revolutionary Vladimir Ilyich Ulyanov, also known as Lenin, at Izmailovo flea market in Moscow on December 3, 2017. (Photo by Mladen Antonov/AFP Photo)

A Dancer, dressed with the traditional Yi costume, waits to perform at the Torch Festival, in Xichang, China's Sichuan province on July 27, 2016. As a result of fast urbanisation in the rural area of China Like Lienchang prefecture, the traditional costume is fading away for the Yi people in daily life. (Photo by Fred Dufour/AFP Photo)