A new campaign has been launched in Greece’s Santorini to urge tourists to refrain from taking donkey taxis, asking them to think twice before riding donkeys and mules after some of the animals are found to be suffering from exhaustion, spinal injuries and saddle sores.

The campaign, called “In Their Hooves”, is managed jointly by a UK-based charity, The Donkey Sanctuary, and Cruise Lines International Association (CLIA), which transports as many as 17,000 passengers to the island every day during summer.

“We hope visitors to Santorini are able to make informed decisions about the welfare of working equines they will see there,” Barbara Massa, The Donkey Sanctuary’s regional director for Europe, said in a statement.

“We will continue to work with the municipality, providing training to equine health service providers and also the animal owners, all of whom are critical to improving the working conditions and practices on the island,” she added.