Fort Collins, Colorado, is currently captivated by the mysterious sightings of rabbits with bizarre, horn-like protrusions. These animals, nicknamed “Frankenstein bunnies” and “zombie rabbits,” have ignited a viral sensation across social media platforms.

The origin of these unsettling features, however, is rooted in science rather than the supernatural. This phenomenon is linked to folklore, historical medical research, and a naturally occurring virus. Here’s a closer look at the facts.

What’s Causing the “Horns” on These Rabbits?

The strange growths result from the Shope papillomavirus, a disease that dates back to its discovery in the 1930s. Passed on through fleas, ticks, and mosquitoes, it causes wart-like tumors that can develop into long, horn-like structures. Though their appearance is disturbing, experts assure that the virus poses little threat to wild rabbits unless the tumors interfere with essential functions like seeing or eating.

Kara Van Hoose, a Colorado Parks and Wildlife spokesperson, explains:

“It exhibits as these wart-like growths on their face—sometimes they’re smaller, like little nodules, and sometimes they’re bigger, like tentacles or horns.”

Resident Susan Mansfield described one infected rabbit:

“It looks like black quills or black toothpicks sticking out all around his or her mouth. I thought he would die off during the winter, but he didn’t. He came back a second year, and it grew.”

From Folklore to Fact: The Jackalope Connection

The virus isn’t new—it’s believed to have inspired the mythical jackalope, a rabbit-antelope hybrid from North American folklore. Dr. Richard Shope’s 1930s research on the virus even contributed to understanding HPV’s link to cancer.

Social media users have amplified the bizarre sightings with creative nicknames:

“This is how the zombie virus starts.” – Instagram user 

“We’ve got freaking zombie rabbits now?!” – YouTube comment

Despite the horror-movie comparisons, Van Hoose reassures:

“Nature is metal, and this can be kind of cool looking on different rabbits.”

Should Humans Be Worried?

The virus does not spread to humans, pets, or other wildlife. However, officials warn against touching infected rabbits, as interference can stress the animals.

Domestic rabbits face greater risks, as the virus can escalate into aggressive cancers. Veterinarian Thomas M. Donnelly notes:

“The majority [of domestic rabbits] develop invasive epidermoid carcinomas, which are typically fatal.”