European rabbits are in decline in rural areas, yet holding strong in cities. But urban living also comes with a changed lifestyle: instead of being packed into complex burrows, city rabbits seem to live a more solitary life in smaller burrows.
Madlen Ziege from the University of Frankfurt, Germany, and her colleagues studied the burrow structures of several populations of European rabbits from urban, suburban and rural sites in and around Frankfurt.
They found that the closer to the city the burrows were, the smaller, simpler and less populated they became. "I did not expect to find such a clear correlation," says Ziege.
So why are urban rabbits downsizing? For one thing, rabbits usually form larger groups when food and burrowing sites are in short supply. Surprisingly, this is not the case in cities, where rabbits may colonise parks, for example.
"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," says Ziege. "Many areas in modern cities are often structurally highly diverse and the urban rabbit population could be benefiting from this."
In contrast, she says, rural areas in Germany are now typically characterised by open landscapes with scarce vegetation cover.
Predator pressure
Living in large groups also helps rabbits conserve heat in winter, but there is less need to do that in cities where the microclimate tends to be warmer. Then there is the threat from predators.
"In rural areas, rabbits might be exposed to higher predator pressures and are therefore forced to live in large burrows," says Néstor Fernández of the Doñana Biological Station in Seville, Spain. Complex burrows with many exits help rabbits survive attack, but are clearly a major undertaking. "Building burrows requires investing a lot of energy, and individual rabbits can increase their fitness living and contributing to expand existing burrows, particularly under high predator pressure."
It's unclear whether similar patterns in burrow types will be found across Europe, but Ziege says more research could give us key insights into successfully managing rabbit populations and avoiding damage they may cause to vegetation and even buildings.
European rabbits are listed as near threatened by the IUCN, with populations in decline especially in Spain and Portugal, which they are native to.
Cities have the potential to serve as new habitats for wildlife and in the case of Germany they might even play an important role by acting as a "source" from which rabbits can recolonise rural areas, Ziege says.
Journal reference: Journal of Zoology, DOI: 10.1111/jzo.12207
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