Bats in the City

Studying our nocturnal neighbours

Urbanisation and wildlife

Since 2007 and for the first time in history, more people live in cities and towns than in rural areas. Further urban sprawl is unavoidable given the expected rapid growth of the global population (estimated 2.5 billion people by 2050). The process of urbanisation transforms natural landscapes in an extreme manner and often requires the modification or complete loss of natural habitats. Urbanisation can be critical for biodiversity given that this process normally includes an increase of impervious surfaces (i.e. buildings and roads), increased pollution, altered hydrology as well as increased urban noise and artificial light. Some species disappear completely from cities given that they rely on habitat features or ressources that are not found in cities. Other species adapt to these anthropogenically altered landscapes and some species even benefit from these areas. The different responses of wildlife to urbanisation typically results in altered species communities, with a few highly abundant species in urban areas compared to surrounding natural ones. Furthermore, wildlife populations in urban areas might be exposed to additional stress, sensory pollution, increased infection and parasitism rates, lower reproduction rates or might even alter their behaviour.

Urbanisation and bats

Bats are an interesting group of animals to study the impact of urbanisation on wildlife. They are a highly diverse group of mammals that occur worldwide; also in urban environments. Generally, increased urbanisation has been found to cause a decline in bat species richness and activity. Nevertheless, the effect of urbanisation on bats seems to be rather complex and bats show species-specific responses to urbanisation. While some bat species can, for instance, take advantage of buildings as roosting sites or street lamps as foraging grounds, other species are not able to adapt to these anthropogenic structures or even avoid them. In a recent meta-analysis on global urban bat studies it was proposed that behavioral and morphological (e.g. high wing loadings and aspect ratios) traits of bats determine if a species is able to adapt to urban areas (Jung and Threlfall, 2016). Further, studying urban bats in relation to natural habitat surroundings (e.g. forested or grassland regions) is crucial to better explain the potential negative or positive effect of urbanisation on different bat species. Bat colonies in buildings might lead to human-wildlife conflicts and might also be more exposed to opportunistic predators which are predominantly abundant in urban areas (such as crows, rats or domestic cats). Our understanding of what influences the species success to adapt to the urban environment and what ensures their survival in these areas is still limited. However, given the ongoing global urban growth, species conservation depends arguably upon this knowledge.

Why studying bats in Berlin

Berlin is a unique place to study the behavioural and morphological traits of urban bats. Given the political separation and reunificant, we find today different concepts of urban development in the Eastern and Western parts of Berlin; consisting of a variety of green spaces, waterways and unused sites. The surrounding of Berlin is characterised by agricultural and forest land. Furthermore, Berlin’s bat fauna is with 18 bat species (some species have only a seasonal occurence) species-rich and Berlin holds some crucial winter roosting sites, such as the Zitadelle in Spandau. 

 

At the Bat Lab at the IZW, we aim to gain a better understanding of underlying mechanisms that enable bat species to adapt to urban environments which can inform authorities to create bat-friendly cities in which people and bats can share the same habitat. Research until today has involved bats at street lights in Berlin (Lewanzik and Voigt, 2017) and the foraging behaviour of Noctules bat (N. noctula). We have set up long-term study sites to study the rural-urban coupling of bat populations and to understand the movement ecology of bat citizens.