A zookeeper feeds a hippopotamus with a watermelon in its enclosure in Belgrade's zoo, Serbia, July 20, 2015. Temperatures in Serbia have risen up to 40 degrees Celsius (104 degrees Fahrenheit), according to official meteorological data. (Photo by Marko Djurica/Reuters)

Newborn sea lion “Kaya” crawls at the enclosure at the zoo in Wuppertal, Germany July 23, 2015. Kaya was born on July 4, 2015 in the zoo, officials said. (Photo by Ina Fassbender/Reuters)

Atsushi Abe and Yumi Adachi from Japan perform in the synchronised swimming mixed duet technical routine preliminary at the Aquatics World Championships in Kazan, Russia July 25, 2015. (Photo by Michael Dalder/Reuters)

Farmers herd a flock of ducks along a street towards a pond as residents drive next to them in Taizhou, Zhejiang province, June 17, 2012. (Photo by Reuters/China Daily)

Protesters take part in “Artists Take Fight Against Police Murders” in New York's Times Square August 13, 2015. (Photo by Brendan McDermid/Reuters)

A worker holds harvested chillies at a chilli plantation in Pasir Datar Indah village near Sukabumi, Indonesia's West Java province, August 6, 2015. (Photo by Reuters/Beawiharta)

People perform during the traditional Epiphany parade in Malaga, southern Spain, January 5, 2016. Children in Spain traditionally receive their Christmas presents delivered by the Three Wise Men on the morning of January 6, during the Christian holiday of the Epiphany. (Photo by Jon Nazca/Reuters)

A passenger not wearing pants sits in a subway train during the “No Pants Subway Ride” in Prague, Czech Republic, January 10, 2016. The event is an annual flash mob and occurs in different cities around the world in January, according to its organisers. (Photo by David W. Cerny/Reuters)