Bat research for conservation – a Latvian-German success story
December 18, 2025
Text: Jan Zwilling
Photos: Jon A. Juarez
They live hidden under the protection of darkness, but behind the fleeting shadows at dusk lie fascinating animals: bats are the only mammals fully capable of flying and are famous for their ability to orient themselves using echolocation. With the exception of the polar regions, more than 1,500 species can be found all over the world and play important roles in their ecosystems, for example as seed dispersers, pollinators or insectivores. However, anthropogenic environmental changes are affecting them. Humans illuminate the night, reduce important food sources and disrupt the migration routes of migratory species. Understanding and protecting bats is therefore the goal of a Latvian-German success story in science: for over 10 years, scientists from the Latvia University of Life Sciences and Technologies, the University of Latvia, the University of Oldenburg and the Leibniz Institute for Zoo and Wildlife Research in Berlin have been working together at the Pape Ornithological Station in Latvia to unravel the secrets of bats. In August 2025, the German ambassador to Latvia, Gudrun Masloch, visited the Pape Station and accompanied the researchers in their work.
Between shallow lakes, high dunes and the Baltic Sea lies a unique biological research station. Where the border with Lithuania is very close and the capital Riga is far away, the Latvian “Papes Ornitoloģijas stacija” – the Pape Ornithological Station – has existed for over half a century. Every year, scientists from all over Europe come here to study the migratory behaviour of birds. Well over a million birds have so far been caught in large nets, carefully examined, some of them ringed and all released back into the wild. But it is not only birds that populate the sky above Pape; the station is also located on an important migration route for bats. Wildlife biologists specialising in bats are working with Latvian colleagues in Pape to conduct ground-breaking basic research and applied conservation research.
A few more steps through the fine sand of the dunes, and Gudrun Masloch stands in the middle of the ‘gate’ of the world's largest bat trapping facility, a funnel-shaped net trap with an opening 50 metres wide and 15 metres high. It is aligned along the bats' late summer migration route from north to south. Masloch is the German ambassador to Latvia and travelled from Riga to Pape on a late summer's day in August 2025 to see the station and the German-Latvian research cooperation on bats with her own eyes. Moments earlier, she had met Dr Gunārs Pētersons from the Latvia University of Life Sciences and Technologies and Dr Oskars Keišs from the University of Latvia, as well as their German colleagues Dr Oliver Lindecke from the Carl von Ossietzky University of Oldenburg and Prof. Dr Christian Voigt from the Leibniz Institute for Zoo and Wildlife Research in Berlin. “I am very impressed by the high level of motivation and scientific standards at this unique research station”, says Masloch. “The German and Latvian scientists have been working closely together for many years, like a family. And the local residents here, the students from the universities, are all part of a deeply rooted community. It's wonderful to see.”
As Masloch and the scientists marvel at the net trap, the afternoon sun casts long shadows in the sand. But the secrets of bats are not revealed during the day; the scientists have to work night shifts to track down the animals. During the trapping season, the large net trap is raised at dusk by hand using rope winches, and bats fly into the soft nets until late at night. At the end of the funnel, many hands, landing nets and headlamps are in use, carefully removing the animals from the nets so that they can be examined by a vet and, depending on the research question, equipped with a miniaturized biologger, for example.
“Ten years ago, we knew very little about bat migration. Where exactly they fly, where they rest, how they manage the enormous energy expenditure of a flight lasting several thousand kilometres”, says Voigt. Research in Pape has shed a great deal of light on this mystery. A study by the Leibniz-IZW, conducted partly in a wind tunnel and a breathing chamber and partly in Latvia, investigated the energy requirements and travel speed of migrating Nathusius' pipistrelles. A wind tunnel experiment was used to determine the animals' energy requirements for different flight speeds. The breathing chamber allowed Voigt and his team to precisely measure the accumulation of stable carbon isotopes in the bats' breath and thus calculate their metabolism. They repeated measurements directly before and after flights in the wind tunnel at different speeds and were thus able to determine the speed at which the best ratio of energy consumption to distance travelled occurs. The field study in Latvia revealed the actual speeds of migrating bats. “Our study proves that the observed flight speeds match the calculated ideal values exactly. The bats therefore fly at precisely the speed that is most energy-efficient over long distances”, says Voigt. This speed is approximately 7.5 metres per second, or 27 kilometres per hour.
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Pape is a dark place, one where night can still be night. In many places in Europe, this is no longer the case, and the time between dusk and dawn is never really dark anymore. And Pape is a wild place where the seasonal migration of birds and bats can still be studied in a largely unspoilt landscape. In this respect, the rest of the continent cannot quite keep up as well. However, watering holes for resting are becoming rarer and wind turbines are turning centuries-old migration routes – such as from the Baltic States to the south of France – into a dangerous obstacle course. These turbines have now also moved closer to the station in Latvia. Animals tagged in Pape are also providing information about the exact routes taken by migrating bats and which locations for wind turbines are particularly risky for bats. But how do bats orient themselves when hunting or migrating in the dark? Voigt and Lindecke have researched their sense of sight, echolocation and a mysterious “sixth” sense:
Humans see with their eyes, bats “see” using echolocation? However, the situation is not quite so black and white, because these light-sensitive animals do respond to visual stimuli during their long flights, as the research groups led by Voigt and Lindecke discovered. In a series of experiments in Pape, for example, they were able to prove that Soprano pipistrelles (Pipistrellus pygmaeus) and Nathusius' pipistrelles (Pipistrellus nathusii) are attracted to red light sources during migration. For the study in Pape, the researchers erected an eight-metre-high mast on which a plastic board was illuminated or remained dark at 10-minute intervals. Red or white LED light was used alternately for illumination. Microphones recorded the echolocation of the bats flying past to determine which species passed the illuminated or unilluminated light field and how often. The result: white light had no influence on the presence of bats, whereas red light had a significant influence. Soprano pipistrelles and, to a lesser extent, Nathusius' pipistrelles were detected more frequently during the red-light phases than in darkness.
The crucial thing is that the red light used in the experiment corresponds to the colour of the warning lights on wind turbines. “Bats are exposed to an increased risk of collision with wind turbines during their autumn migration. Our study suggests that the use of red warning lights could have fatal consequences for migrating bats”, explain Voigt and Lindecke. “Red warning lights, known as beacons, are often installed so that they are visible for many kilometres. They could therefore attract migrating bats over long distances.”
Another study by Lindecke and colleagues in Pape revealed that this sensitivity to light sources should come as no surprise. “To our surprise, we found that bats observe the sun at sunset and use it to adjust their navigation system at night”, says Lindecke. “If the animals were as light-shy as they are commonly believed to be, they would avoid sunset and would not be able to reliably adjust their night-time compass. In fact, they seem to consciously use the residual light. It is therefore not surprising that artificial light sources can also influence their behaviour, depending on the colour, brightness and direction of the light and the situation in which the animals find themselves.”
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Gudrun Masloch and the small group of bat scientists from Latvia and Germany leave the first dune wall behind them and visit one of the wooden huts that serve as laboratories or workrooms for the research teams from home and abroad. In a Mongolian yurt specially equipped for bat flight studies, Lindecke shows a Nathusius' pipistrelle and a Parti-coloured bat that were caught the previous night for research purposes. “Being so close to the animals and at the same time getting explanations from the researchers was very fascinating for me”, says Masloch. “Above all, I learned how many questions in basic research are still open here or are only just being answered – for example, about how bats orient themselves. In the end, the research methods are not that complicated or time-consuming, but they are very creative and intelligent.” During the conversation, the Parti-coloured bat sits quietly on the cloth held by Lindecke and patiently allows itself to be examined. Even smaller and lighter than the bat, which weighs only 7 grams, is the miniaturized biologger that can be attached to the bats' backs and records valuable data on their spatial flight behaviour. Whether on a small scale, providing information about orientation and movement during hunting, or on a large scale, providing information about flight routes and dangers during seasonal migration, the transmitter data is key to understanding the sensory abilities of bats.
“We specifically anaesthetised the cornea in order to test a hypothesis discussed in the specialist literature: that microscopic magnetic iron oxide particles in the cornea act as a compass and provide directional information from the Earth's magnetic field via nerve pathways. As expected, bats from the control group and the group with unilateral corneal anaesthesia oriented themselves towards the south, while animals with bilateral corneal anaesthesia flew off in random directions”, explains Lindecke. “In a separate experiment, we showed that the anaesthesia did not impair the animals' visual light-dark perception. The findings suggest that the cornea feeds a non-visual, presumably magnetic sense of orientation, which temporarily fails when blocked on both sides. This opens up new avenues for specifically investigating the navigation system of migratory mammals.”
Not only biologgers attached to bats, but also complex microphone arrangements provide information about the migratory behaviour of bats in Pape: For a study conducted in collaboration with the Max Planck Institute for Behavioural Biology in Konstanz, Voigt, Lindecke and Gunārs Pētersons set up eight ultrasonic microphones at defined intervals on a metal rod on the Latvian Baltic coast. This study enabled them to refute the assumption that all bats take the same route during their seasonal migration in late summer from northern Europe along the coastlines to their wintering grounds in central and western Europe. The reality is more complex: In late summer, most of the animals flew south, but on some days, a fifth of them flew in the opposite direction, northwards, presumably due to weather conditions. Because bats stay along the coastlines longer than previously known and sometimes also veer out to sea and fly “detours”, wind turbines pose a greater danger than previously assumed.
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Pape is an indispensable research site for all these findings in basic and applied research. But that's not all: the station is a cluster of expertise that offers more than just location and infrastructure. For many years, it has been headed by Oskars Keišs, who is also a scientist at the University of Latvia, where he heads the ornithology laboratory. The main focus of his research is on the factors that directly or indirectly explain changes in bird populations – for example, anthropogenic influences such as climate change and hunting. In Pape, he gained experience with both birds and bats. Together with international researchers such as Voigt and Lindecke, he is able to draw exciting comparisons between the biology of bats and birds. In doing so, he also supports the DFG Collaborative Research Centre 1372 “Magnetic Reception and Navigation in Vertebrates: From Biophysics to Brain and Behaviour”, within which Lindecke leads a subproject on the magnetic orientation of migrating bats under laboratory conditions and in free flight.
Keišs' colleague Gunārs Pētersons from the Latvia University of Life Sciences and Technologies has been ringing bats in Pape for more than three decades – an outstanding treasure trove of knowledge for bat research. Recoveries of these ringed animals in France, Spain and other countries have provided important insights into the distance and direction of the late summer migration to the south-west.
When Masloch leaves the station in Pape, night has long since fallen and the team has put the trapping equipment into operation. Bat after bat is cared for by the participants working hand in hand. Professors and students, seniors and young people, Germans and Latvians, professionals and volunteers. “Beyond the value for science and species conservation, one thing in particular stuck with me from my visit to Pape: projects and initiatives like this help us to network internationally and not forget how to work in communities across borders”, Masloch reflects. “And it is very valuable that we live in a world where we can make such cooperation possible, for example through the European Union. We depend on each other a lot and can do many things very well in a complementary manner. Pape is a very good example of how cooperation can succeed internationally in the long term and what added value it has. Science can play an important role in finding solutions together and resolving conflicts of interest.”