City bats have a more varied diet than their rural relatives

Insectivorous bats such as the common noctule find less food in cities than in the countryside – yet their diet is more varied. This was demonstrated by a scientific team led by the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) in an article published in the journal “Landscape and Urban Planning”. Using genetic analyses of faecal samples, they showed that common noctules in Berlin consumed 55 per cent more insect species than their conspecifics in the surrounding rural regions. Also, urban bats consumed twice as many ‘pest’ insect species and six times as many ‘nuisance’ species such as mosquitoes than their rural counterparts.

Urbanisation generally leads to a decrease in biodiversity. Nevertheless, a mosaic of highly fragmented but very different habitats in cities such as Berlin can also promote a relatively high diversity of insects, for example. Insects are an important food source for bats. A scientific team led by Prof Dr Christian Voigt and Dr Carolin Scholz from the Leibniz-IZW has now investigated the diet of the common noctule (Nyctalus noctula) in Berlin and neighbouring rural regions. The team collected bat faecal samples over three years and analysed them using the metabarcoding method to identify the bat species from which the faecal samples originated, as well as the insect species in the diet as documented by the faecal samples. They detected a total of 129 insect species in the faecal samples of the common noctule. The most frequently detected were a midge species, the acorn weevil beetle and the bark and a wood-boring beetle.

The diet of the common noctules in Berlin proved to be significantly more diverse than that of their relatives from the surrounding countryside. “Although there are fewer insects in the city overall and urban bats are less successful hunters, which means that they consume fewer insects than their relatives in the countryside, the composition of their diet is on average 55 per cent more diverse”, summarises Scholz. “The urban bats consumed 83 insect species that were not on the menu of their rural counterparts, whereas bats in rural areas only fed on 27 species exclusively. Only 15 per cent of the detected prey species were found in both urban and rural habitats.” This could be a result of the greater diversity of food available in small areas in the city and the larger foraging range of urban bats. “Insects are less common and relatively isolated in urban areas. This could mean that bats in cities hunt opportunistically rather than focussing on specific prey, which leads to a more diverse diet”, says Scholz.

The greater diversity of the diet is also reflected in the presence of ‘pests’ and ‘nuisance” insects such as mosquitoes that the common noctules consumed. Around a third of the insect species detected in the faecal samples were species that are considered agricultural pests (20 species) or nuisance insects (6 species). Two thirds of the urban samples and a good half of the rural samples contained at least one of these species. “All in all, common noctules in Berlin consumed around two and a half times as many agricultural pests as their rural counterparts”, says Voigt. “In the case of nuisance insects such as mosquitoes, there are even six times as many species in the city bats’ diet.” This emphasises the importance of bats as ecosystem service providers for humans – particularly in cities. Bats obviously can “help” the human urban population by consuming potential disease vectors. This is becoming increasingly important in times of spreading diseases such as West Nile virus and dengue fever. For this reason, among others, the city should hold onto its mosaic of different, valuable habitats. Dark corridors connecting these fragmented food sources should be protected and developed so that bats can make better use of them and provide us with this service.

Publication

Scholz C, Teige T, Djoumessi KPN, Buchholz S, Pritsch F, Planillo A, Voigt CC (2024): Dietary diversification of an insect predator along an urban-rural gradient. Landscape and Urban Planning Volume 256, April 2025, 105273. DOI: 10.1016/j.landurbplan.2024.105273

Contacts

Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW)
in the Forschungsverbund Berlin e.V.
Alfred-Kowalke-Str. 17, 10315 Berlin, Deutschland

Prof Dr Christian Voigt
Head of the Department of Evolutionary Ecology
phone: +49(0)30 5168 511
email: voigt@izw-berlin.de

Dr Carolin Scholz
Scientist in the Department of Evolutionary Ecology
phone: +49(0)30 5168 515
email: scholz@izw-berlin.de

Jan Zwilling
Science communication
phone: +49(0)30 5168121
email: zwilling@izw-berlin.de