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

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

DENVER—A group of rabbits in Colorado with grotesque, hornlike growths may seem straight out of a low-budget horror film, but scientists say there’s no reason to be spooked—the furry creatures merely have a relatively common virus.