From multifamily residences to studio apartments: shifts in burrow structures of European rabbits along a rural‐to‐urban gradient

Abstract

European rabbits (Oryctolagus cuniculus) are currently declining in most rural areas throughout central Europe, while city populations often reach high densities. We asked whether and how altered environmental conditions affect the social organization and burrow structures of European rabbit populations located at urban, suburban and rural sites in and around Frankfurt a.M. in Germany. Burrow densities (numbers per ha) increased along the rural-to-urban gradient, accompanied by a gradual shift from accumulated towards more evenly distributed burrows. Burrows became smaller and less complex with increasing degree of urbanity, and accordingly, also the number of rabbits inhabiting the same burrow decreased. It remains unclear whether urbanization first led to smaller rabbit group sizes and burrow structures then shifted as a consequence of this, or vice versa. Nevertheless, for both scenarios, 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 characterizing most rural areas in central Europe.

Population genetics of the European rabbit along a rural-to-urban gradient

“…By contrast, urbanization in the metropolitan area of Frankfurt and the associated typical changes in landscape structure and habitat types (e.g., mosaic-like land-use patterns) seem to have a neutral or even a positive effect on the genetic diversity of European rabbit populations, as our analyses revealed higher heterozygosity and reduced inbreeding with increasing urbanization. However, our results are not surprising for an 'urban adaptor'-such as the European rabbit-that during our sampling period occurred at high population densities in German cities 17,26,46,49 . Habitat heterogeneity, increased availability of resources, and low densities (or absence) of predators and competitors are among the hypothesized factors explaining the successful colonisation of cities by European rabbits 49 .…”

“…Since the degree of urbanization does not necessarily decrease continuously towards the outskirts of a city 52 , we refrained from categorizing our sites into distinct classes and instead calculated a continuous variable, the "urbanity index" 46,49 . To this end, we incorporated several variables related to the degree of both, anthropogenic www.nature.com/scientificreports www.nature.com/scientificreports/ disturbance and landscape alterations.…”

How weather instead of urbanity measures affects song trait variability in three European passerine bird species

“…The principal component analysis for the urbanity parameters was based on the “degree of urbanity” introduced by Ziege et al. () and was adjusted with relevant urbanity parameters for birds, like the building density and height.…”

“…Therefore, we performed principal component analyses for all song parameters, for all frequency, structure, urbanity, and weather parameters (Tables 1 and 2). The principal component analysis for the urbanity parameters was based on the "degree of urbanity" introduced by Ziege et al (2015) and was adjusted with relevant urbanity parameters for birds, like the building density and height.…”

“…This might for example be due to high buildings with many reflective surfaces which might modulate sound transmission. Therefore, to infer human influence on bird song, it is important to consider the degree of urbanization in addition to ambient noise alone (Bókony et al, 2012;Giraudeau et al, 2014;Seress, Lipovits, Bókony, & Czúni, 2014;Ziege et al, 2015).…”