Though the horned rabbits aren’t a danger to humans or pets, Van Hoose advises people to keep their distance from the creatures, as they should with any wild animal, because rabbits can pass along other pathogens. “Once you realize these probably aren’t harmful to rabbits, you can kind of appreciate the science at work,” she says.

Photos of the cottontails inspired nicknames like “Frankenstein bunnies,” “demon rabbits” and “zombie rabbits.”

Rabbits in northern Colorado have been spotted with bizarre, somewhat grisly horns on their face. Shope papillomavirus is known to affect only rabbits and hares, not humans or other animals, says Kara Van Hoose,