The image of a rabbit with horns has persisted in human culture for centuries, appearing in folklore, taxidermy, and even scientific drawings. While a typical, healthy rabbit does not possess true bony horns or antlers, the persistent visual evidence of a “horned rabbit” is rooted in biological reality. These unusual protrusions are the physical manifestation of a specific viral infection affecting the animal’s skin cells. The resulting growths, which can appear strikingly horn-like, stem from a dermatological condition that transforms the rabbit’s appearance.
Separating Folklore from Biological Reality
The most prominent cultural representation of the horned rabbit is the jackalope, a creature of North American folklore, often depicted as a jackrabbit with the antlers of a deer or antelope. This mythological figure gained widespread popularity in the 1930s following a taxidermy prank by the Herrick brothers in Douglas, Wyoming, who grafted deer antlers onto a rabbit carcass. The resulting mounted specimen became an enduring symbol of the American West.
The myth’s deeper origins likely predate this modern taxidermy stunt, with references to horned hares appearing in European natural history texts as far back as the 16th century. Researchers suggest that many historical sightings were inspired by real rabbits exhibiting grotesque, horn-like masses. These observations were the earliest, often misunderstood, documentation of a specific viral condition that alters the rabbit’s external form.
The Viral Culprit Cottontail Rabbit Papillomavirus
The true cause of the “horned” appearance is the Cottontail Rabbit Papillomavirus (CRPV), also known as the Shope papillomavirus. First described in 1933 by scientist Richard Shope, this virus is a member of the Papillomaviridae family, which causes warts and tumors in various animal species. CRPV specifically targets lagomorphs, the order that includes rabbits and hares, and is common in wild cottontail rabbit populations.
The virus functions by infecting the epithelial cells of the rabbit’s skin, specifically targeting the basal layer where new skin cells are produced. Once inside, the viral DNA hijacks the cellular machinery, utilizing early oncogenes like E6 and E7 to initiate uncontrolled cell division. This rapid, unregulated proliferation of skin cells results in the formation of large, warty tumors, technically known as papillomas.
Anatomy and Appearance of Keratinous Tumors
The growths produced by CRPV are not made of bone, distinguishing them entirely from the true horns of cattle or the antlers of deer. Instead, they are highly keratinized tumors, composed primarily of keratin, the tough, fibrous protein found in the rabbit’s hair, claws, and outer skin layers. This dense protein structure gives the growths their hard, dark, and often rough appearance, making them resemble small, spike-like horns or tree branches.
These papillomas can emerge anywhere on the rabbit’s body, but they are most frequently observed on the head and face, often clustering around the mouth, eyelids, and ears. Their size can vary significantly, starting as small, reddish bumps and progressing into large masses several centimeters in length. While the growths are initially benign, they can sometimes progress to a more serious malignancy called squamous cell carcinoma, especially in domestic rabbit species.
Disease Progression and Ecological Impact
For many wild cottontail rabbits, the infection is often self-limiting, with the growths eventually regressing as the rabbit’s immune system mounts a response. However, the disease can be severe and life-threatening for rabbits with a weaker immune response or those with tumors in restrictive locations. Growths around the eyes can obstruct vision, increasing the rabbit’s vulnerability to predators.
The most serious impact comes from tumors developing around the mouth and jaw, which physically impede the rabbit’s ability to graze and feed. This obstruction often leads to malnutrition or starvation, a common cause of death for heavily infected animals. The virus is primarily transmitted through biting arthropods, such as mosquitoes and ticks, which carry the infectious agent to a new host through a break in the skin. This transmission method means the disease’s prevalence is higher during warmer months when insect populations are most active.