Viral photos have inspired a fluffle of unflattering nicknames, including "Frankenstein bunnies," "demon rabbits" and "zombie rabbits."

Colorado Parks and Wildlife say rabbits in Fort Collins are infected with rabbit papilloma virus, causing horn- or tentacle-like growths.

Some cottontail rabbits in Fort Collins, Colorado, have been drawing attention because they have wart-like growths on their faces that look like horns.