A photographer tested the concentration of several pairs of dogs as he captured their reactions to treat time in a series of shots. Christian Vieler, 47, of Waltrop, Germany, has been a professional dog photographer since 2016. He came up with the idea of snapping two dogs catching treats simultaneously. Here: Basset Hounds. (Photo by Vieler Photography/Caters News Agency)

Russian pop art photographer Sergey Chilikov captures a nation liberated from the social oppression of late-era Soviet rule – at parties, in the streets, and bouncing high. His exhibition, Photoprovocations, will be at Photo London, 19-22 May. Here: Yoshkar-Ola, Matrosova Street (1995). (Photo by Sergey Chilikov)

Unforgiving temperatures of up to 60℃ (140℉) beat down on these saltminers on a daily basis. The mines, situated in the Afar Triangle in Ethiopia, stretch across 38,000 sq miles and at their lowest point are more than 300ft below sea level. Joel Santos travelled to capture the area’s dry, brutal beauty. Here: Dromedaries and donkeys are used to transport the salt. (Photo by Joel Santos/Barcroft Images)

The twin lighthouses of St Joseph on Lake Michigan have been transformed by a winter storm. Ice encases the buildings, giant icicles hang from the piers and the beach is frosted white. Here: Huge icicles hang from the pier. (Photo by Mike Kline/Barcroft Media)

These horses are pictured in the Khentii province in eastern Mongolia during the Winter Horse Festival – where skillful horsemen gather to challenge the strength of their horses and show off their riding skills. Pictures were taken by Batzaya Choijiljav, a travel company director from Mongolia. Here: The fur of a horse ices up in the –40 cold of Mongolia. (Photo by Batzaya Choijiljav/Caters News)

These tiny insects are so well camouflaged it is nearly impossible to make out their cleverly disguised forms. Canadian photographer and adventurer Paul Bertner attempted to catch the bugs in their natural habitats as part of a hide-and-seek game to show biodiversity in nature. Here: Stick insects. (Photo by Paul Bertner/Caters News)

Ten finalists capture the theme of “through young eyes” in this young photographers’ competition that aims to engage youth around the world in wildlife conservation. Here: Heavy bodied jumping spider by Md Rashuidul Rabby, age 23, from Bangladesh. (Photo by Md Rashuidul Rabby/WWD2017)

Planned improvements to Rio’s favelas have meant increases in rent, forcing the poorest families into squatting in unoccupied buildings. Photographer Tariq Zaidi visits the Mangueira community favela, less than 1km from the showpiece Maracanã stadium, to see what life is like for the women living there. Here: Victoria, 12, at her home in Mangueira. (Photo by Tariq Zaidi/The Guardian)