When domesticated rabbits go feral, new morphologies emerge

Associate Professor Emma Sherratt, from the University of Adelaide’s School of Biological Sciences, led a team of international experts to assess the body sizes and skull shapes of 912 wild, feral and domesticated rabbits to determine how feralisation affects the animal.

“Feralisation is the process by which domestic animals become established in an environment without purposeful assistance from humans,” says Associate Professor Sherratt, whose study was published in Proceedings of the Royal Society.

“While you might expect that a feral animal would revert to body types seen in wild populations, we found that feral rabbits’ body-size and skull-shape range is somewhere between wild and domestic rabbits, but also overlaps with them in large parts.

“Because the range is so variable and sometimes like neither wild nor domestic, feralisation in rabbits is not morphologically predictable if extrapolated from the wild or the domestic stock.”

Associate Professor Sherratt, who performed this study as part of her ARC Future Fellowship, says the greater diversity seen in the skull shape of feral rabbit populations could be related to changes in evolutionary pressures.

“Exposure to different environments and predators in introduced ranges may drive rabbit populations to evolve different traits that help them survive in novel environments, as has been shown in other species.

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

“In particular, relaxed functional demands in habitats that are free of large predators, such as Australia and New Zealand, might drive body size variation, which we know drives cranial shape variation in introduced rabbits.” she says.

Associate Professor Sherratt plans to follow up this research by looking into what environmental factors drive the observed variation in body size and skull shape of Australia’s feral rabbits.

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

“And we focus on skull shape because it tells us how animals interact with their environment, from feeding, sensing and even how they move.

“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, and how we may mitigate their success.”