The National Park Service took to social media last week to discourage visitors from searching for and licking Sonoran Desert toads, also known as Colorado River toads.

The toads can “secrete a potent toxin” to defend themselves against predators — but some people are deliberately ingesting the toxin to experience hallucinations and other psychoactive effects.

However, the park service said the toxin “can make you sick” and said they should be left alone.

“As we say with most things you come across in a national park, whether it be a banana slug, unfamiliar mushroom, or a large toad with glowing eyes in the dead of night, please refrain from licking,” the post added.