Details on the emergence of horny 'demonic' rabbits in the US

Groups of wild rabbits spotted in the Fort Collins area (about 105 kilometres north of Denver, Colorado, USA) have caused a flurry of discussion on social networks: the animals have bizarre growths on their muzzles, which has led to them being dubbed "Frankenstein's rabbits", "demon rabbits" and "zombie rabbits".

Biologists explain: we are not talking about mutants and not about a dangerous outbreak, but about a virus common to rabbits - Shope papillomavirus (Shope papillomavirus), which most often runs relatively harmless.

According to experts, in eastern cottontails rabbits, the virus causes wart-like growths that can extend to resemble "horns". It's these growths that have come to the attention of citizens in recent weeks, prompting calls to the Colorado Parks and Wildlife Department. Department spokeswoman Kara Van Hoose said such cases are not uncommon, especially in the summer, when fleas and ticks - the vectors of the infection - are more active. The virus is transmitted between rabbits but does not infect people or pets, she said.

The growths themselves are usually not dangerous. They become a problem if they grow in the eye or mouth area and interfere with vision or eating. In most cases, the animal's immune system copes: as the papillomas heal, they shrink and eventually disappear.

The phenomenon has long been known to science and culture. Scientists believe that it was observations of "horned" rabbits that may have fuelled North American folklore about the "jackalope" - the mythical hare with horns. Research into the disease in rabbits almost a century ago also helped to better understand the link between viruses and cancer - similar to how in humans certain types of papillomavirus are linked to the development of cervical cancer.

The virus is named after Dr Richard E. Shope, a Rockefeller University professor who described the disease in wild bunny rabbits in the 1930s. Today, experts emphasise that summer "outbreaks" are due to the seasonal activity of vectors and the fact that people are more likely to see wild animals in urban environments during the warm season.

If you see a rabbit with such growths, officials recommend keeping a distance and not trying to help yourself: in most cases, the animal recovers without intervention, and assess its condition should be wildlife professionals. The main thing is to understand that "horns" do not make these rabbits dangerous to people and pets.