Biology subjects

Lindecke, O.

Publications and source records attributed to Lindecke, O..

7 recordsLinked to original sources

bioRxiv2026

Compass orientation of a migratory mammal in total darkness

Many animals use the Earth's magnetic field to orient and navigate over long distances, yet the sensory mechanism that underlies this ability remains unresolved. A central question is whether the compass depends on light: a cryptochrome-based radical-pair mechanism, best characterised in birds, requires a photon to generate the magnetically sensitive species, whereas magnetic particle-based and inductive mechanisms do not. In mammals, which lack the light-sensitive cryptochromes that the avian model requires, this question is unresolved. Here we tested whether migratory bats, Pipistrellus nathusii, require light for migratory orientation, studying wild migrants at a major flyway under laboratory-controlled light conditions, including verified total darkness. Bats were acclimated to starlight-level illumination or to total darkness before release into a circular arena in which take-off direction was recorded, and take-off latency was taken in every trial as a control for behavioural state. Bats released under starlight-level illumination, and bats released in total darkness after starlight acclimation, both oriented in the south-westerly direction typical of free-flying bats at this flyway; their mean headings lay 11 degrees apart and did not differ in direction, in angular concentration, or in take-off latency. Bats released in total darkness after prolonged darkness produced the same mean heading but did not reach significance under a Rayleigh test, and did not differ from either other group. To our knowledge, this is the first demonstration that a migratory mammal expresses its seasonally appropriate migratory heading in total darkness. Bats orienting in darkness took off five to eight minutes after their last photon exposure, seven to eight orders of magnitude beyond the microsecond lifetime of the only cryptochrome radical pair demonstrated to exist and to be magnetically sensitive. Because a compass reading is informative only at the moment of the directional decision, a signal generated before a bat entered darkness could not encode its heading at take-off; the magnetically sensitive species must therefore form without photons. The radical pairs capable of doing so have not been shown to exist, even in vitro. A migratory mammal thus expresses its seasonal heading without concurrent light, in a lineage lacking the photoreceptor on which the light-dependent compass in birds relies.

animal behavior and cognition↗

bioRxiv2025

Timing of circadian shifts in light/dark preference by migratory bats supports targeting of sunset for magnetic compass calibration

Bats are nocturnal mammals whose migrations depend on the precise timing of activities to exploit favourable conditions, such as tailwinds and high insect activity, while evading predators. Understanding how migratory bats use sensory cues within their roosts to time emergence requires knowledge of the interplay between circadian rhythms, spatial cognition, and seasonal demands. We examined light-dark choice in tree-dwelling Nathusius pipistrelles (Pipistrellus nathusii) over an 18-hour cycle using a Y-maze. Bats preference for the lit exit increased prior to sunset, then switched back to preferring darkness only near sunrise. This behaviour contrasts with that of previously studied cave-dwelling bats. Irrespective of their exit choice, bats used echolocation in all trials, consistent with a multimodal sensory strategy in which light conveys critical environmental information beyond the range of echolocation, but not replacing it. However, light governed the time-dependent shift in exit selection. The circadian shifts in light/dark preference are consistent with two hypotheses related to navigation mechanisms and stopover behaviour: Preference for light cues may facilitate compass calibration mechanisms, whereas the dawn preference for darkness likely reflects roost-searching and predator avoidance. These findings underscore the integral role of vision in bat navigation and highlight how circadian rhythms modulate photic responses in a migratory context. Such insights are essential for designing wildlife-friendly lighting and for interpreting future multi-sensory experiments, including those probing bat magnetoreception, where natural photic responses must be taken into account.

animal behavior and cognition↗

bioRxiv2025

Sounds of silence: electric mobility promises a quieter soundscape for wildlife, but may challenge ultrasonically sensitive species globally

Expanding transportation networks generate anthropogenic noise, a stressor for wildlife. The rapid transition to electric mobility, with projections of 40-45 million new electric vehicles (EVs) annually by 2030 (two in five new light-duty vehicles), promises quieter audible environments. However, a critical gap exists in our understanding of the acoustic trade-offs, especially of vehicle-generated ultrasound (frequencies >20 kHz). While ultrasound is known to be biologically potent, used for instance in wildlife repellents, its presence and potential impacts as an emission from traffic on sensitive species, such as bats, remain unaddressed. While the shift to EVs may reduce overall audible noise emissions, offering a green alternative, potential challenges for species with auditory systems tuned to ultrasound, and also actively using it via echolocation, could offset these benefits. This may set up a green-green dilemma, as the objective of decarbonising transport via e-mobility may undermine efforts to restore urban biodiversity. Our systematic review of 49 studies on anthropogenic/vehicular noise impacts on 114 bat species/species groups revealed that road noise, especially when overlapping with bat echolocation and communication frequencies, consistently elicited negative responses in playback experiments, whereas field observations were more variable. A meta-analysis from this dataset showed that the odds of bats being affected significantly increased with both noise intensity and frequency. Building on this evidence, this review explores the implications for a future dominated by EVs. We highlight the urgent need for further research to define acoustic thresholds and develop conservation strategies for wildlife in rapidly urbanising and electrifying landscapes.

ecology↗

bioRxiv2023

Orientation tests and long-term movement phenology establish the red admiral Vanessa atalanta as an applicable model for navigation research in migratory butterflies

Animal migrations are disappearing globally, while insect populations are on alarming declines. Both ecosystem degradations, influenced by unpredictable impacts of climate change, are also exacerbated by human activities such as intensified land use and various forms of environmental pollution. Butterfly migrations may serve as sensitive indicator phenomena of these broader environmental changes. While the transcontinental journeys of one of the most famous Lepidopteran species, the North American monarch butterfly, Danaus plexippus, are documented in depth, they are a geographically restricted phenomenon. Comprehensive studies from other areas and on other migratory butterflies like the European red admiral, Vanessa atalanta, are notably sparse. In addition, the details of their navigational capacities and how they might be affected by the aforementioned changes remain largely enigmatic. Against this backdrop, we seek to establish the red admiral as a model for insect movement phenology and navigation behaviour which both might be impacted by environmental changes. Employing a combination of orientation tests, utilizing flight-simulators and free-flight trials during late summer, together with a 23-year study on movement phenology at a coastal migration flyway, the Baltic Sea coast, we offer broad insights into red admiral migration. In our experiments, butterflies exhibited a southwestern orientation on the Courish Spit and chose a south-southeastern trajectory in free-flight trials after translocation at the Latvian Baltic Sea coast. Directional records from decades-long trapping data, based on more than 16,000 individuals, match these findings. Nevertheless, we also found reverse movements to occur under some circumstances. At the same time, the observed estimated median dates of red admiral passages did change by one day only between decades, however, generally more butterflies were recorded in recent years. Our data thus suggest a certain degree of adaptability in the butterflies movement behaviour, indicating an innate migration schedule, possibly supported by a flexible navigational capacity. As the world is facing biodiversity loss at a high rate, long-term monitorings of indicator species become important. By establishing the red admirals as a model for butterfly migration, we expect insights into broader movement patterns and navigational strategies in Lepidoptera negotiating human-dominated environments, filling a crucial gap in our current understanding of these interdependent aspects of insect biology.

zoology↗

bioRxiv2023

Migratory bats are sensitive to magnetic inclination during compass calibration

The Earths magnetic field is used as a navigational cue by many animals. For mammals, however, there is little data to show that navigation ability relies on sensing the natural magnetic field. In migratory bats, however, the calibration of a magnetic compass became plausible following experiments demonstrating a role for the solar azimuth at sunset in their orientation system. Here, we investigated how an altered magnetic field at sunset changes the nocturnal orientation of the bat Pipistrellus pygmaeus. We exposed bats to either the natural magnetic field, a horizontally shifted field (120{degrees}), or the same shifted field combined with a reversal of the natural value of inclination (70{degrees} to -70{degrees}). We later released the bats and found that the take-off orientation differed between all treatments. Bats that were exposed to the 120{degrees} shift were unimodally oriented northwards, in contrast to controls which exhibited a North-South distribution. Surprisingly, the orientation of bats exposed to both a 120{degrees}-shift and reverse inclination was indistinguishable from a uniform distribution. These results provide the missing link that these migratory bats calibrate a magnetic compass at sunset, and for the first time, they show that bats are sensitive to the angle of magnetic inclination.

animal behavior and cognition↗

bioRxiv2022

A playback paradox? Nathusius' bats, Pipistrellus nathusii, bypass mating and fueling opportunities on migratory transit flights

In late summer, migratory bats of the temperate zone face the challenge of accomplishing two energy-demanding tasks almost at the same time: migration and mating. Both require information and involve search efforts, such as localizing prey or finding potential mates. In non-migrating bat species, playback studies showed that listening to vocalizations of other bats, both con-and heterospecifics, may help a recipient bat to find foraging patches and mating sites. However, we are still unaware of the degree to which migrating bats depend on con- or heterospecific vocalizations for identifying potential feeding or mating opportunities during nightly transit flights. Here, we investigated the vocal responses of Nathusius pipistrelle bats, Pipistrellus nathusii, to simulated feeding and courtship aggregations at a coastal migration corridor. We presented migrating bats either feeding buzzes or courtship calls of their own or a heterospecific migratory species, the common noctule, Nyctalus noctula. We expected that during migratory transit flights, simulated feeding opportunities would be particularly attractive to bats, as well as simulated mating opportunities which at the same time indicate suitable roosts for a stopover. However, we found that the echolocation call activity of P. nathusii decreased during the playback of conspecific feeding buzzes and courtship calls, yet the call activity remained unaffected when heterospecific call types were broadcast. Our results therefore suggest that while on migratory transits, P. nathusii circumnavigate conspecific feeding and mating aggregations, possibly to save time or to reduce the risks associated with social interactions. This avoidance behavior could be a result of optimization strategies by P. nathusii when performing long-distance migratory flights.

animal behavior and cognition↗

bioRxiv2020

In situ novel environment assay reveals acoustic exploration as a repeatable behavioral response in migratory bats

Integrating information on species-specific sensory perception together with spatial activity provides a high-resolution understanding of how animals explore environments, yet frequently used exploration assays commonly ignore sensory acquisition as a measure for exploration. Echolocation is an active sensing system used by hundreds of mammal species, primarily bats. As echolocation call activity can be reliably quantified, bats present an excellent animal model to investigate intra-specific variation in environmental cue sampling. Here, we developed an in situ roost-like novel environment assay for tree-cave roosting bats. We repeatedly tested 52 individuals of the migratory bat species, Pipistrellus nathusii, across 24 hours, to examine the role of echolocation when crawling through a maze-type arena and test for consistent intra-specific variation in sensory-based exploration. We reveal a strong correlation between echolocation call activity and spatial activity. Moreover, we show that during the exploration of the maze, individuals consistently differed in spatial activity as well as echolocation call activity given their spatial activity, a behavioral response we term acoustic exploration. Acoustic exploration was correlated with other exploratory behaviors, but not with emergence latency. We here present a relevant new measure for exploration behavior and provide evidence for consistent (short-term) intra-specific variation in the level at which wild bats collect information from a novel environment.

animal behavior and cognition↗