A wolf looks into the camera at the 30 km (19 miles) exclusion zone around the Chernobyl nuclear reactor in the abandoned village of Orevichi, Belarus, March 2, 2016. What happens to the environment when humans disappear? Thirty years after the Chernobyl nuclear disaster, booming populations of wolf, elk and other wildlife in the vast contaminated zone in Belarus and Ukraine provide a clue. (Photo by Vasily Fedosenko/Reuters)

A man takes pictures at the finish line during the Colour Run at Centennial Park in Sydney August 25, 2013. According to organizers, 15,000 runners registered to complete the 5km (3 miles) course in Centennial Park on Sunday, being covered in blue, pink, orange and yellow powder on their way to the finish line. (Photo by Daniel Munoz/Reuters)

Olga Gharkova enters a aromatherapy room at the British Banya bathhouse, Saturday, February 15, 2014, in Krasnaya Polyana, Russia, just a few miles away from the ski slopes where athletes are competing for Olympic medals. (Photo by Jae C. Hong/Associated Press)

A participant of the Wild Sau Dirt Run 2015 passes a mud barrier in Obertriesting, Lower Austria, Austria, Saturday, April 4, 2015. The Wild Sau Dirt Run is a cross country and steeplechase race for men and women over the distances of 5, 10 and 20 kilometers (3.1, 6.2 and 12.4 miles). (Photo by Ronald Zak/AP Photo)

Tour de France hostess wear face masks prior to the start of the first stage of the Tour de France cycling race over 156 kilometers (97 miles) with start and finish in Nice, southern France, Saturday, August 29, 2020. (Photo by Christophe Ena/AP Photo)

Riders compete during a kok boru, also called ulak tartysh, a traditional game in which players on horseback manoeuvre with a goat's carcass and score by putting it into the opponents' goal outside Sokuluk village, 20 km (12,5 miles) west of Bishkek, Kyrgyzstan, Tuesday, March 30, 2021. (Photo by Vladimir Voronin/AP Photo)

Melissa Stewart's team competes in the official restart of the Iditarod, a nearly 1,000 mile (1,610 km) sled dog race across the Alaskan wilderness, in Fairbanks, Alaska, U.S. March 6, 2017. (Photo by Nathaniel Wilder/Reuters)

Paramedics care for a woman who is ill after the Geelong Cup on Geelong Cup day at Geelong Racecourse in Melbourne, Australia, 19 October 2016. The Geelong Racing Club was founded in March 1865 at a public meeting at the British Hotel. The first Geelong Cup was held in 1872 over a distance of two miles. (Photo by Tracey Nearmy/EPA)