Photographer Andy Hall joins the thousands of fans from west Africa who have gathered for Baaba Maal's annual Blues du Fleuve festival in Senegal. Here: Dancers wait to perform on stage. (Photo by Andy Hall/The Observer)

Indian Hindu devotees wait to take part in an event to mark Pongal in Mumbai on January 15, 2016. Pongal, which coincides with the Hindu festival Makara Sankranthi, is a thanksgiving and harvest celebrated throughout India and specifically by those from the Indian state of Tamil Nadu. (Photo by Indranil Mukherjee/AFP Photo)

Images created with Post-it notes are seen in the windows of offices at 75 Varick Street in lower Manhattan, New York, U.S., May 18, 2016, where advertising agencies and other companies have started what is being called a “Post-it note art war” with employees creating colorful images in their windows with Post-it notes. (Photo by Mike Segar/Reuters)

The carcass of a yacare caiman lies in the dried-up river bed of the Pilcomayo river in Boqueron, Paraguay, August 14, 2016. In Paraguay, alongside the Pilcomayo River, black vultures flew over a shrinking pond where a group of crocodilian reptiles known as yacare caimans sought refuge. Water from the river, which divides Paraguay and Argentina in the area of the Gran Chaco, was scarce. This is not an uncommon sight in the region of General Diaz, about 700 kilometres (435 miles) northwest of the country's capital Asuncion, where the Pilcomayo's waters form lakes and streams that give life to capybaras, birds and caimans. (Photo by Jorge Adorno/Reuters)

“Double head vulture”. On the day of windy days during raptors migration some people in my country start to catch these tired raptors, so in this day we go to photograph some raptors and we saw these tow tired vultures, so we start to drag them away from the hunters until they reach a good hidden place, to make them safe until they start a new journey. Photo location: Kuwait. (Photo and caption by Mohd Khorshed/National Geographic Photo Contest)

Kashmiri vegetable vendors assemble at a floating market in the interiors of the Dal Lake in Srinagar April 17, 2012. (Photo by Danish Ismail/Reuters)

In a new project, an international group of photographers have joined forces to use their powerful images to raise awareness and funds to help stop the illegal wildlife trade. Here: Fennec foxes are captured for the illegal pet trade. This three-month-old pup was for sale in a market in southern Tunisia. (Photo by Bruno D'Amicis/Photographers Against Wildlife Crime/Wildscreen/The Guardian)

Anfisa, a twelve-year-old female chimpanzee, picks its nose at the Royev Ruchey Zoo in a suburb of the Siberian city of Krasnoyarsk, Russia on October 18, 2017. (Photo by Ilya Naymushin/Reuters)