Sheep walk as they are herded to summer pastures in Serra da Estrela, near Seia, Portugal June 27, 2015. In late June, shepherds young and old in the Seia region of central Portugal start guiding sheep, goats and cattle to the Serra da Estrela, the country’s highest mountains, in search of better pastures. There they stay until the end of September. Modern-day shepherds may have mobile phones to keep in touch with family and friends, but their lifestyle has changed little for centuries. The sound of cowbells and the bark of longhaired mastiffs starts early in the morning as the animals – often decorated with traditional woollen balls on their horns – are herded up steep, narrow paths. (Photo by Rafael Marchante/Reuters)

A woman dressed up for Halloween travels on a Metro train in São Paulo, Brazil on October 30, 2017. (Photo by Cris Faga/Rex Features/Shutterstock)

A herder stops for reindeers to have a rest while riding along the tundra area in Nenets Autonomous District, Russia, November 27, 2016. In Russia's remote Arctic regions reindeer herding has been a way of life for centuries. Each winter herders in Russia's sparsely populated Nenets Autonomous District corral their reindeers into open-air pens before selecting weak animals to be culled... (Photo by Sergei Karpukhin/Reuters)

A groom leads his horse in the equine pool after working out on the track, during early morning workouts for the upcoming Derby race in Mumbai January 29, 2015. (Photo by Danish Siddiqui/Reuters)

Granada’s International Poetry Festival is an extraordinary celebration of poetry that takes place across the entire city. For a week, every February, Granada is transformed into a virtual Capital of the World’s Poetry. Photo: A girl takes part in the “Burial of arrogance and haughtiness” carnival during the IX Poetry Festival in Granada, 45 km from Managua, Nicaragua on February 20, 2013. In this occasion the festival is dedicated to Nicaraguan poet Ernesto Cardenal. (Photo by Hector Retamal/AFP Photo)

A woman works at the H. Upmann cigar factory during the XX Habanos Festival in Havana, Cuba on March 1, 2018. From the field to the factory during the annual Habanos cigar festival in Cuba. (Photo by Reuters/Stringer)

Internally displaced Syrian children who fled Raqqa city stand near their tent in Ras al-Ain province, Syria January 22, 2017. (Photo by Rodi Said/Reuters)

A handout photograph provided by Brian Kubicki of Costa Rican Amphibian Research Center on 26 April 2016 shows a “Crystal frog”, Hyalinobatrachium dianae (H. diane). This frog was discovered by US biologist Brian Kubicki and Costa Ricans Stanley Salazar and Robert Puschendorf in a rainy forest of Costa Rican caribbean after 40 years without notice of any new example of this kind. (Photo by Brian Kubicki/EPA/Costa Rican Amphibian Research Center)