Fort Collins, Colorado – Residents of northern Colorado were startled this week after spotting a group of rabbits with bizarre horn-like growths on their heads, earning them eerie nicknames like “Zombie Rabbits” and “Frankenstein Bunnies.” While their appearance sparked alarm and fascination, wildlife experts say the phenomenon is not dangerous.
The unusual growths are caused by Shope papillomavirus, a relatively common virus among wild rabbits that leads to horn-like tumors on the head and face. Photos of the animals, taken in Fort Collins about 65 miles north of Denver, quickly spread across social media, fueling speculation and comparisons to horror movie creatures.
“This is not something people need to panic about,” said Kelsey Van Hoose, spokesperson for Colorado Parks and Wildlife. She explained that outbreaks are more frequently observed during the summer months, when flea and tick populations—known carriers of the virus—are at their peak.
Though unsettling, the virus poses no risk to humans or pets. “It only spreads among rabbits,” Van Hoose added.
Shope papillomavirus is far from a new discovery. First identified in the 1930s by Rockefeller University professor Dr. Richard Shope, the virus has fascinated scientists for decades. Its ability to cause tumor-like growths helped researchers better understand the connection between viruses and certain types of cancer, including human papillomavirus (HPV), which can lead to cervical cancer.
Historians also note that sightings of horned rabbits likely inspired North American folklore about the “jackalope,” a mythical creature described as a rabbit with antelope-like horns. The viral images of Colorado’s so-called “Zombie Rabbits” have revived interest in that legend, blending science, myth, and viral internet culture.
While experts emphasize the condition is not rare, its disturbing appearance ensures that every fresh sighting captures public imagination. For now, Fort Collins’ horned rabbits remain a striking reminder of how nature and folklore often intertwine.
