Team Strong Silvers member Ngai Hin Kwok, 66, works out as teammate Ng Siu Chi, 57, watches at a stadium in Singapore March 15, 2015. Team Strong Silvers, is a group of senior citizens who train in calisthenics. The trio trains individually at least three times a week, and meets up for joint calisthenics at least twice a month. (Photo by Edgar Su/Reuters)

One-year-old female giant panda cub Nuan Nuan reacts inside her enclosure during joint birthday celebrations for the panda and its ten-year-old mother Liang Liang at the National Zoo in Kuala Lumpur on August 23, 2016. Giant pandas Liang Liang, aged 10, and her Malaysian-born cub Nuan Nuan, 1, were born on August 23, 2006 and August 18, 2015 respectivetly. (Photo by Mohd Rasfan/AFP Photo)

The British Ecological Society has announced the winners of its annual photography competition, Capturing Ecology. Taken by international ecologists and students, the winning images will be exhibited at the society’s joint annual meeting in Ghent in December. Here: Overall runner-up; Toucan, Mark Tatchell. (Photo by Mark Tatchell/British Ecological Society)

A South Korean soldier wear North Korea's military uniform, acting as North Korean soldier during an anti-terror and anti-chemical drill session held as part of the 2011 Ulchi Freedom Guardian (UFG) event on August 17, 2011 in Seoul, South Korea. The 11-day UGC, which features drills including the handling of chemical and biological attacks, is a regular joint exercise between US and South Korean troops to prepare for potential emergencies on the Korean Peninsula. (Photo by Chung Sung-Jun/Getty Images)

A French Air Force Mirage 2000 fighter jet takes off during the close air support (CAS) exercise Serpentex 2016 hosted by France in the Mediterranean island of Corsica, at Solenzara air base, March 17, 2016. Serpentex is an annual exercise that involves joint terminal attack controllers (JTACs) from 12 countries from March 7 to March 25, 2016. (Photo by Charles Platiau/Reuters)

A patient buried in the hot sand looks out from under a shade that protects his face from the sun in Siwa, Egypt, August 12, 2015. In the searing heat of summer in western Egypt, at the hottest time of the day, sufferers of rheumatism, joint pain, infertility or impotence lie buried neck-deep in the sand of Siwa near Dakrour Mountain. Locals say taking a sand bath is a natural therapy with powers to cure many medical conditions. (Photo by Asmaa Waguih/Reuters)

People use snowshoes during a tour of the Great Kemeri Bog, Latvia, October 17, 2015. The Kemeri bog is more than 8,000 years old and is one of the largest dry moss swamps in the Baltics. A more than decade-long joint restoration of the bog by the European Union and the Latvian government helped the bog recover its high moss marshes, damp black alder forests, floodplain meadows and seaside lakes – features now considered rare in Europe due to industrialisation. (Photo by Ints Kalnins/Reuters)

Women walk next to soldiers in Surcubamba, Peru, Thursday, May 21, 2015. The Joint Command of the Peruvian Armed Forces organized a humanitarian mission to Surcubamba, where health care was provided to families from nearby villages in this region called VRAEM, the acronym for Valley of the Apurimac, Ene and Mantaro rivers, where sixty percent of Peru's cocaine originates. (Photo by Rodrigo Abd/AP Photo)