A video showing an alleged assault was posted online and uploaded to YouTube by Italian animal rights association, Animalisti Italiani.
“Police called me yesterday to tell me they have intervened following our reports and are investigating the sexual abuse suffered by the poor donkey,” Animalisti Italiani vice president Pier Paolo Cirillo told Rome-based daily, Il Messaggero.
The alleged offender is a middle-aged man who kept a flock of sheep in the park. He is reported to have made and sold cheese products from their milk at premises inside the park.
His business activities are now being investigated by fiscal and sanitation authorities.
To date, none of the animals belonging to the man have been sequestered by the police but Animalisti Italiani has offered to give the donkey a new home.
“We have told the police we could send it to one of our animal oases where many animals that have been saved from various situations live,” Crillo added.
Laws governing zoophilia vary around the world. Denmark only recently made it illegal and it is still legal in other European countries such as Finland and Romania.
While Italy has no specific laws against zoophilia, Italy's top court has ruled against it in the past. In 2012 the Court of Cassation sentenced a man to six months in jail for forcing his dogs to have sex with women.