Residents of Fort Collins, Colorado, have been spotting wild rabbits with eerie, horn- and tentacle-like growths sprouting from their heads and faces. These alarming sightings—reminiscent of “Frankenstein bunnies” or “zombie rabbits”—are attributed not to mutation, but to a known viral infection.

What’s Causing the Growths?

Wildlife experts from Colorado Parks and Wildlife confirm that the culprit is Shope papillomavirus (also called cottontail rabbit papillomavirus). This virus triggers wart-like tumors—typically around the head, ears, and eyelids—that may elongate into horn-like structures.
These lesions are primarily cosmetic, as they rarely pose serious threats unless they obstruct the rabbits’ ability to see or eat. Most wild rabbits recover naturally over time.

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Spread and Risks

The virus transmits between rabbits—often via biting insects like fleas, ticks, or mosquitoes during warmer months. It remains specific to rabbits and does not pose risks to humans, pets, or other wildlife.
However, domestic rabbits can suffer more severe outcomes and may require veterinary care for removal of tumors.

Why the Frenzy?

These grotesque visuals have sparked broad interest—and mythologizing. The condition may have inspired the “jackalope” legend—North America’s mythical horned rabbit. The connection also played a foundational role in early cancer research, especially around papillomaviruses.

Local residents are advised to steer clear of these rabbits and avoid contact. While visually striking, the phenomenon is not unprecedented and highlights intriguing intersections of nature, folklore, and scientific discovery.