A participant of the sled dogs race in action with the dogs in Stroehen (Lower Saxony), Germany, 18 October 2015. It is the first round of the North German Championship. (Photo by Peter Steffen/EPA)

A Filipino worker arranges roasted pigs which they sell in suburban Quezon city, Philippines on Tuesday, December 23, 2014. Roasted pig is popular during Filipino celebrations and traditionally served during a Christmas eve dinner called “Noche Buena” in this predominantly Roman Catholic nation. (Photo by Aaron Favila/AP Photo)

An Afghan refugee girl shows her younger brother a calf in a slum on the outskirts of Islamabad, Pakistan, Friday, February 6, 2015. (Photo by Muhammed Muheisen/AP Photo)

“Just hanging out”. As full autumn hits the valley of Hallingdal in Norway, this bear chills out in a tree which seems to barely cover its weight. Photo location: Flå, Hallingdal, Norway. (Photo and caption by Jorgen Tharaldsen/National Geographic Photo Contest)

Miniature spring-wound 35-mm film camera in a modified cigarette pack. The Tessina’s small size and quiet operation provided more options for concealment than most commercially available models. (Photo by Central Intelligence Agency)

People look at French artist Clement Briend's photographic light installation “Divine Trees”, which features images of divine figures highly revered in Asian cultures projected on trees towering over bystanders, during a media preview of the Singapore Night Festival in Singapore August 21, 2014. The Singapore Night Festival begins on Friday. (Photo by Edgar Su/Reuters)

Two biplanes of the Team Breitling cross during a training flight prior the AIR14 air show in Payerne, Switzerland, August 29, 2014. (Photo by Peter Schneider/EPA)

“Warming up”. This photo I capture in the early afternoon, the animal species of lemurs fly. Photo location: Sambas, West Kalimantan, Indonesia. (Photo and caption by Hendy Mp/National Geographic Photo Contest)