Recently, The National Park Service offered a rather strange reminder for folks visiting one of its national parks: Do not lick the toads.

Organ Pipe Cactus National Monument in Arizona, part of the UNESCO biosphere reserve, is home to the Sonoran Desert Toad, also known as the Colorado River Toad. Measuring about 7 inches in length, it is one of the largest toads in North America, and it makes a low-pitched “ribbit” sound that is familiar in the region.

Toads have no teeth or claws, so this species of toad protects itself from predators by secreting a potent toxin that can make other animals or humans sick if they touch it or ingest it. The neurotoxin is secreted by external skin glands on the back, neck, and shoulders of the toad.

“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 agency wrote on Facebook last week.

Licking the Sonoran Toad can cause muscle weakness, rapid heart rate, and vomiting.

However, the practice of licking toads is gaining traction, according to the Addiction Center, because the neurotoxin can also produce a psychedelic high in those who ingest it. The toad’s secretion contains a powerful hallucinogenic known as 5-Meo-DMT.

This chemical can be extracted from the toad’s glands and dried into a paste. The paste can then be smoked, causing the user to experience a trip. Smoking this substance has grown in popularity in recent years — so much so that the toad has been declared a threatened species in New Mexico.

Several individuals have reported experimenting with the toads’ extracted toxins, most notably boxing legend Mike Tyson, and the son of the president, Hunter Biden, who claimed in his memoir that 5-MeO-DMT therapy is a form of addiction treatment.

The United States Drug Enforcement Administration classifies the drug 5-MeO-DMT as a Schedule 1 drug, meaning it is currently not accepted for medical use and has a high potential for abuse.