European rabbit
European rabbits live in smaller burrows with fewer rabbits in citiesAlex J./Flickr

City rabbits are sacrificing space for the perks of city living, scientists have found, with urban European rabbits living in smaller burrows with fewer companions.

The species of rabbit, mainly found in south-west Europe and northern Africa, is currently declining in most rural areas across Europe, yet populations in cities are increasing.

Experts at the University of Frankfurt, Germany, were looking to find out how "altered environmental conditions affect the social organisation and burrow structures".

Publishing their findings in the Journal of Zoology, the researchers discovered that burrow densities increased in rural areas: "Burrows became smaller and less complex with increasing degree of urbanity, and accordingly, also the number of rabbits inhabiting the same burrow decreased."

Speaking to New Scientist, study author Madlen Ziege said they were not expecting to find such a clear correlation.

"Cities are providing a constant and high food supply through human waste and deliberate feeding, as well as access to vegetation cover, such as shrubs," she said. "Many areas in modern cities are often structurally highly diverse and the urban rabbit population could be benefiting from this."

In rural areas, rabbits tend to live together to conserve heat. In cities, generally warmer temperatures mean this is not as great a requirement.

Researchers also believe the reduced predator pressures could mean smaller, less complex burrows are needed. "It remains unclear whether urbanisation first led to smaller rabbit group sizes and burrow structures then shifted as a consequence of this, or vice versa," the authors wrote.

Currently, the European rabbit is listed as near threatened on the IUCN Red List, with hunting, habitat loss and disease all leading to a decreasing population. Researchers say the move to cities could provide them with a new home.

"We propose that increased structural heterogeneity of urban landscapes is the major factor behind the observed effects, as mosaic-like habitat patches in cities provide high and steady resource availability compared with the agriculturally transformed, open landscapes characterising most rural areas in central Europe."