How light pollution disrupts orientation in moths

(Press-News.org) Moths are under threat from increasing light pollution: streetlights and other artificial light sources in cities and populated areas disrupt the orientation of these nocturnal insects, which reduces their chances of mating. Scientists have been studying the effects of streetlights on moths for years but remain largely in the dark about the underlying mechanisms. The Lightstar project aims to provide new insights. “We want to create a more detailed database on how light pollution affects the behaviour of moths” says project leader Dr Jacqueline Degen. The biologist has secured a prestigious European Research Council (ERC) Starting Grant worth 1.5 million euros over five years for her research at the University of Oldenburg.

ERC Starting Grants are awarded to outstanding researchers in the early stages of their career. “The prestigious ERC Grant is a great success for Jacqueline Degen,” said Professor Dr. Ralph Bruder, President of the University of Oldenburg. “Her project bolsters our exceptional research in the field of animal navigation and therefore our NaviSense Cluster of Excellence, too.” Scientists at the University of Oldenburg will be pooling their pioneering research in the field of navigation in animals such as migratory birds, bats, krill and insects in this cluster from January 2026.

Tracking moths with ultra-lightweight responder

Moths are known as the “bees of the night” and play an indispensable role in ecosystems: they pollinate (crop) plants and are an important source of food for other animals such as bats and birds. The significant decline of insect populations worldwide consequently poses a serious problem. Degen wants to determine how factors such as moonlight, street lighting, the weather and cloud cover interact and affect the behaviour of privet hawk moths and elephant hawk moths. These moth species use the moon and stars to navigate and often travel long distances in search of food. The rising moon also compels them to seek mates. Degen’s hypothesis is that artificial light impairs spatial orientation in male moths and thus hampers their search for females that are willing to mate.

Degen and her team are developing an innovative 3D tracking system that will enable them to study moths in detail in previously unexplored spatial and temporal dimensions. “We will attach a responder that is as small as possible to the moth’s back,” explains Degen. “Then, with the help of a specially built drone, we will be able to track its flight trajectory and altitude over hundreds of metres for the first time ever.” The tricky aspect is that not only must the responders be extremely light but they must also be reliably detectable under real nocturnal natural conditions. Although ultra-light reflective responders weighing around 20 milligrams already exist, it is not yet clear whether they will work outdoors at night. “Grasslands are often damp at night,” explains Degen. “Dew on plants can create strong, uncontrolled reflections that will probably be difficult to distinguish from the relevant transponder signals.”

The aim of the project is therefore to develop specially adapted lightweight responders and evaluation methods that provide a clearly identifiable signal even under these difficult conditions. In the long term, the scientists hope to create responders that are light enough to be used not only on larger moths, but also on extremely small insect species.

Insect decline: reduction of light pollution

The new 3D tracking system will also be used in large-scale field experiments. “We will release male moths out in the open, about 100 metres away from the females,” explains Degen. “When the males fly off in search of the females we will simulate street lighting along the route, with the moon in the background.” In these field experiments, the researchers aim to study the interactions between moonlight, street lighting, cloud cover, wind, moth flight duration and flight altitude.

“Our research can contribute to the development of effective strategies to counteract insect decline caused by light pollution,” explains Degen. The data it provides could serve as a basis for political decisions on ways to reduce artificial lighting in public spaces, for example. Even small measures such as placing lamps at a lower height so they don’t disrupt the flight corridors of moths could be helpful, the biologist stresses.

About Dr. Degen

Dr Jacqueline Degen studied biology at Bielefeld University and the University of Würzburg. She completed her PhD titled “Exploratory behavior and landmark learning in the honey-bee” at the Freie Universität Berlin. In 2016, she returned to the University of Würzburg and headed two research projects at the Chair of Behavioural Physiology and Sociobiology. In August 2025, Degen joined the Insect Spatial Orientation and Navigation Lab research group led by navigation biologist Professor Dr. Basil el Jundi at the University of Oldenburg. Her Lightstar research project, in which one postdoc and two doctoral candidates are to be employed, will be launched in February 2026.

END