The Real Story Behind Colorado’s “Frankenstein Rabbits”: The Rabbits with Horns and Tentacles

What’s Happening in Colorado?

Recently, residents around Fort Collins, Colorado, have spotted wild cottontail rabbits sporting eerie horn- or tentacle-like growths—leading to nicknames like “Frankenstein bunnies” and “zombie rabbits.” These strange protrusions have sparked both concern and fascination across local communities and social media platforms.

The Cause: Shope Papillomavirus

Wildlife experts confirm that these alarming growths are caused by the Shope papillomavirus (also called cottontail rabbit papillomavirus). This virus, first identified in the 1930s by Dr. Richard E. Shope, triggers wart-like, keratinous tumors—some of which can grow long enough to resemble horns or tentacles (Washington Post).

How It Spreads

Transmission typically occurs in warmer months, when ticks, fleas, and mosquitoes are most active. These insects serve as vectors, passing the virus between rabbits. While most wild rabbits recover naturally, severe cases can occur if tumors block vital functions such as eating or seeing (Time).

Are Humans or Pets at Risk?

The virus is species-specific—it cannot infect humans, dogs, or cats. However, wildlife officials caution against handling infected rabbits, as the virus can spread among wild populations or potentially infect domestic rabbits. In pet rabbits, the disease can be more serious, sometimes leading to secondary infections, cancer, or even death. If you own a rabbit, keep it indoors or in secure hutches to reduce contact with wild animals (Axios).

Connection to Folklore

Interestingly, these horn-like growths may have inspired the legendary jackalope, a mythical horned rabbit in American folklore. Taxidermists in the mid-20th century popularized the jackalope image, but the roots of the myth may trace back to sightings of real rabbits infected with the Shope papillomavirus.

Scientific Importance

Beyond folklore, this virus has played a major role in science. Dr. Shope’s research helped prove that viruses can cause cancer—an insight that paved the way for understanding human papillomavirus (HPV) and developing vaccines that prevent virus-related cancers.

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