Whether zoos do more harm or good for the animals they house is hotly debated. What we can all agree on is that anyone who does visit a zoo should abide by its rules and treat the animals with respect. This was upsettingly not the case at La Palmyre Zoo in Royan, France, earlier this month when visitors reportedly etched their names into a rhino’s back.

Photographs of the 35-year-old rhinoceros revealed the names “Camille” and “Julien” scratched into a layer of dust and dead skin on the rhino’s back using fingernails. Guests are permitted to touch the rhinos at La Palmyre Zoo when they come up to the edge of their enclosure, a policy that’s meant to enhance the visitor experience but has been criticized following the incident.

Though the rhino “may not have even realized” what was happening, according to a statement zoo director Pierre Caille made to the Agence France-Presse, the zoo rightfully took to Facebook to express its outrage, a sentiment that was resoundingly echoed on social media. While no harm was ultimately done to the rhino, and no charges will be pressed, it should go without saying that this sort of behavior is unacceptable.