European wild rabbits (Oryctolagus cuniculus) not only achieve high population densities in the city, their burrows are also built more densely and on a smaller external scale. As researchers report, small burrow structures with fewer entrances and exits predominate in Frankfurt's inner city. These structures are inhabited by few animals - often only pairs or single wild rabbits. In contrast to this, the structural systems in the rural environs of Frankfurt are substantially larger and are...