A deer with warts
An image shared on X shows a deer with visible warts. @PetnurseSue/X

An eerie wave of bizarre wildlife sightings has sparked alarm across North America. Reports range from 'Frankenstein rabbits' with horn-like growths, to wart-covered 'zombie squirrels', and now 'mutant deer' marked by flesh-like bubbles.

The unusual appearances have prompted speculation about a possible outbreak, or worse - an 'animal zombie' outbreak. Scientists, however, stress these are long-documented conditions confined to specific species, offering little reason for wider public concern.

From Tentacled Rabbits to Zombie Squirrels

The trend began in Colorado, where rabbits were seen with horn-like protrusions caused by the Shope papilloma virus (SPV). The growths drew comparisons to the mythical jackalope, but authorities emphasised that SPV is a known, largely harmless infection affecting only rabbits. It poses no threat to humans or other animals, AP News reported.

Soon afterwards, grey squirrels across the United States and Canada were observed with wart-like, pus-filled tumours. Dubbed 'zombie squirrels', these cases were confirmed as squirrel fibromatosis, a poxvirus spread through contact or exposure to infected lesions. Experts noted the disease is species-specific and usually resolves naturally, according to the New York Post.

Mutant Deer and a Known Condition

More recently, photographs of deer in states including Pennsylvania, Wisconsin and New York have circulated online, showing ominous blister-like growths. These animals were quickly labelled as 'mutant deer'. Wildlife officials identified the condition as deer cutaneous fibroma, or 'deer warts', caused by a papillomavirus unique to the species. The fibromas are firm, dark, wart-like growths that can range from a pea to a grape or larger.

The Maine Department of Inland Fisheries and Wildlife has said most affected deer carry only a few small fibromas, although more extensive cases sometimes occur. The condition cannot be transmitted to humans or other animals, and in many cases the growths diminish naturally over time. Only in rare, severe cases, such as when vision or feeding is impaired, would intervention be required.

Environmental Triggers and Viral Cycles

The apparent rise in such cases is linked to seasonal and environmental factors. Warm weather accelerates insect activity, particularly ticks and mosquitoes, which play a role in transmitting these viruses between animals. Late summer and early autumn are typically when such conditions peak, The Sun noted.

Some scientists also highlight climate change. Dr Omer Awan of the University of Maryland told the Daily Mail that rising temperatures are allowing vector-borne diseases such as Lyme disease to spread into new areas. The same trend may apply to viruses affecting wildlife. At the same time, the rapid spread of images through social media is amplifying awareness of cases that might once have gone unnoticed.

Understanding the Sightings

The wave of mutant-looking animals, from rabbits and squirrels to deer, can each be traced to species-specific viruses such as Shope papilloma virus, squirrel fibromatosis and deer fibroma. None pose risks to humans or domestic pets. What appears to be an outbreak is the result of natural seasonal cycles, amplified by online visibility.

While the images may be unsettling, wildlife officials recommend observing animals from a distance and allowing nature to resolve the conditions without interference. Experts add that monitoring these outbreaks more closely could also provide early warning of broader ecological changes.

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