Feral Rabbits Evolve in Unexpected Ways

One of the world’s most recognisable domestic animals, the European rabbit. But when domesticated rabbits escape or are released into the wild and become feral, they don’t simply revert to their ancestral form. Instead, they develop entirely new physical traits.

A new study led by Associate Professor Emma Sherratt, a member of the Environment Institute, reveals that feral rabbits evolve novel skull shapes and body sizes that differ from both their domestic and wild counterparts.

Published in the research analysed 912 rabbit specimens across wild, domestic, and feral populations to understand how these animals physically change during the process of feralisation.

“Feralisation is the process by which domestic animals become established in an environment without purposeful assistance from humans,” explains Associate Professor Sherratt.

Contrary to common assumptions, the study found that feral rabbits do not morphologically 'return' to a wild state. Instead, their body size and skull shape sit between those of wild and domestic rabbits, and at times overlap with neither. This suggests that feralisation produces unpredictable outcomes that can’t be reliably forecast by looking solely at domestic or wild traits.

According to the researchers, this variation is likely driven by environmental exposure, predator types, and the freedom to express different traits in less constrained ecosystems.

“Exposure to different environments and predators in introduced ranges may drive rabbit populations to evolve different traits that help them survive,” says Sherratt.

“Alternatively, rabbits may express more trait plasticity in environments with fewer evolutionary pressures.”

Notably, in habitats free of large predators such as Australia and New Zealand, relaxed functional demands may encourage greater body size variation, which in turn influences skull shape diversity.

The study focused on skull shape because it reflects how animals interact with their environment such as how they feed, sense, and move. Among the key findings: allometry (size-related shape changes) and facial tilt emerged as dominant factors driving cranial variation, patterns also seen across the broader rabbit family (Leporidae).

These findings show that both domestication and feralisation have led rabbits to explore new regions of morphospace, the range of physical forms available to them, beyond those occupied by other species in their evolutionary family.

Associate Professor Sherratt plans to follow up the study by investigating what drives the increased body size observed in Australian feral rabbits.

“We found Australian feral rabbits are quite a lot larger than European rabbits. We intend to find out why,” she says.

Understanding these changes not only deepens our knowledge of rabbit evolution but also provides insight into how human-influenced environments can drive morphological diversity in other species.