When domesticated animals escape into the wild, they do not simply revert to their natural state. A new international study on the European rabbit reveals that feralization, the process by which a domestic species establishes a wild population, results in distinct, novel anatomical changes. Led by Associate Professor Emma Sherratt from the University of Adelaide, the research reveals that feral rabbits are not simply reverting to their wild ancestors, but are instead carving out their unique evolutionary path. The findings, published in Proceedings of the Royal Society B: Biological Sciences, provide new insights into how rapidly species can adapt when influenced by humans and new environments.

To understand these changes, the research team analyzed the body sizes and skull shapes of 912 wild, feral, and domesticated rabbits from a global sample. They discovered that while feral rabbits occupy a physical middle ground between wild and domestic populations, their traits are highly variable and often unpredictable. The study found that the main drivers of these changes are allometry, which is the way an animal’s skull shape changes in proportion to its overall body size, and facial tilt. While these are common evolutionary patterns across the entire rabbit family, domestic and feral rabbits have pushed these traits into new territory, creating skull shapes not seen in any other related species.

According to Sherratt, this increased diversity in feral rabbits could be driven by several factors. In some regions, the rabbits may be rapidly adapting to new survival challenges, such as different predators and food sources. “Exposure to different environments and predators in introduced ranges may drive rabbit populations to evolve different traits that help them survive,” she says in a university press release. Alternatively, in environments with fewer threats, such as Australia and New Zealand, which lack many large native predators, there are fewer evolutionary pressures. This “relaxed” environment may allow for a broader range of body sizes and skull shapes to emerge without negative consequences.

The study has significant implications for understanding biological invasions and the rapid evolution of species. By examining rabbit skulls, which provide crucial insights into how an animal feeds, senses its surroundings, and moves, scientists can gain a better understanding of how an invasive species interacts with a new habitat. Sherratt plans to investigate further the specific environmental factors in Australia that have led to its feral rabbits becoming much larger than their wild European counterparts. “Understanding how animals change when they become feral and invade new habitats helps us to predict what effect other invasive animals will have on our environment,” she notes, “and how we may mitigate their success.”

References

• Einem, J. von & University of Adelaide. (2025, July 8). When domesticated rabbits go feral, new morphologies emerge. Phys.Org; University of Adelaide. https://phys.org/news/2025-07-domesticated-rabbits-feral-morphologies-emerge.html

• Sherratt, E., Böhmer, C., Callou, C., Nelson, T. J., Pillai, R., Ruf, I., Sanger, T. J., Schaar, J., Le Verger, K., Kraatz, B., & Geiger, M. (2025). From wild to domestic and in between: How domestication and feralization changed the morphology of rabbits. Proceedings of the Royal Society B: Biological Sciences, 292(2050), 20251150. https://doi.org/10.1098/rspb.2025.1150