The National Park Service is warning outdoor enthusiasts not to lick the Sonoran desert toad. The large amphibians are found across the American southwest, and secrete a potent toxin from glands behind their eyes. While smoking the poison can cause psychedelic effects, ingesting it directly can make humans sick and even be enough to kill a fully grown dog. According to the Oakland Zoo, the toads can grow up to seven inches in length and are identified by their distinctive call, which sounds like a "ferryboat whistle." NPS posted the warning to their Facebook page last week, saying "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."