Prey Availability Determines the Foraging Effort of Bats, Researchers Discover

Bats are amazing animals that play important roles in ecosystems. They pollinate flowers, disperse seeds, and control pests by eating insects.

However, not all bats can adapt to urban environments, where food is scarce and competition is high.

A new study by scientists from the Leibniz Institute for Zoo and Wildlife Research (Leibniz-IZW) reveals how city life affects the foraging behavior and success of a large, insectivorous bat species, the common noctule (Nyctalus noctula).

How do common noctules hunt in cities and rural areas?

(Photo : Hulton Archive/Getty Images)

The researchers used miniature GPS loggers to track the movements of 70 common noctules in Berlin and in a rural area in Brandenburg, Germany.

They also recorded the echolocation calls of the bats to estimate how many insects they caught. They compared the foraging duration, distance, area, and success of the bats in both habitats.

According to the study, city-dwelling common noctules had to hunt longer and farther than their rural counterparts, but they caught fewer insects.

While rural bats hunted together in groups, urban bats foraged alone most of the time. The researchers suggested that this is because urban bats have to compete with other bat species and birds for the limited insect prey.

The study also revealed that urban bats preferred to hunt in green spaces, such as parks and gardens, rather than in built-up areas, such as streets and buildings.

However, even in green spaces, the insect abundance was lower than in rural areas. The researchers say that this could be due to the effects of artificial lighting, noise, and pollution on the insect communities.

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Why do common noctules avoid cities?

The researchers conclude that city life is hard for common noctules because of their poor foraging success.

They say that this could explain why common noctules are less abundant in urban areas than in rural areas, and why they tend to avoid cities during their seasonal migrations.

They also warned that the decline of insect populations due to human activities could further threaten the survival of common noctules and other insectivorous bats.

The study, published in the scientific journal Global Change Biology, is part of a larger project called "Bats and Cities", which aims to understand how urbanization affects bats and how to conserve them.

The researchers hoped that their findings will help raise awareness and appreciation for these fascinating animals and their ecological services.

They also suggested some possible measures to improve the urban habitat for bats, such as creating more green spaces, reducing artificial lighting, noise, and pollution, and installing bat boxes and roosts.

These actions could benefit not only bats, but also other wildlife and human well-being.

Implications for bat conservation and urban planning

The study is one of the first to demonstrate how urban noise can impair the echolocation and foraging performance of bats in a controlled setting.

The findings have important implications for bat conservation and urban planning, as bats provide valuable ecosystem services such as pest control and pollination.

Urban planners and managers should consider the acoustic environment of bats when designing and managing urban green spaces as per the scientists.

They also suggested that creating quiet zones and reducing noise pollution in cities could benefit not only bats but also other wildlife and human health.