Search bioRxiv⌕ Search
Home/Archive/bioRxiv

bioRxiv · 10.64898/2026.10.07.757263

Compass orientation of a migratory mammal in total darkness

Cellarius, F.·Beer, J.·Sucher, K.·Ozolina, A.·Vintulis, V.·Jechow, A.·Lindecke, O.
View original source ↗Export metadata ↓

Abstract

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.

Explore related subjects

animal behavior and cognitionPreprint

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

Cellarius, F., Beer, J., Sucher, K., Ozolina, A., Vintulis, V., Jechow, A., Lindecke, O.. 2026-10-11. Compass orientation of a migratory mammal in total darkness. https://doi.org/10.64898/2026.10.07.757263

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related preprints

bioRxiv2026

Characterizing risky play-like behaviour in juvenile versus young adult rats

Play is an evolutionarily conserved behaviour that contributes to healthy behavioural and neural development. While animal play is traditionally categorized as locomotor, object, or social play, developmental research in children has highlighted the importance of risky play, defined as voluntary engagement with uncertainty and manageable physical risk. Whether similar forms of behaviour occur in non-human animals remains largely unexplored. The present study aimed to establish an ethological framework for identifying and quantifying risky play-like behaviour in rats. Juvenile and young adult male Lister Hooded rats were repeatedly exposed to a custom-designed environment containing elevated and unstable structures that provided opportunities for climbing, balancing, hanging, jumping and social interaction. Behaviour was quantified using two complementary ethograms: a location-based ethogram describing the animal's position within the apparatus and a risky event ethogram capturing selected behaviours associated with physical challenge. By comparing the behaviour of animals during the natural peak of play behaviour with animals beyond this developmental period, we aimed to evaluate whether engagement with elevated and unstable environments reflects play-related processes rather than environmental complexity alone. This study provides a behavioural framework for investigating risky play-like behaviour in rodents and establishes a foundation for future studies examining its developmental and neurobiological significance.

animal behavior and cognition↗
bioRxiv2026

Sensitive period for song learning outlasts parent-offspring cohesion in wild zebra finches

Communication is central to social behaviour, with vocalisations playing a crucial role in many species. In some species, vocalisations are learned, with songbirds being key to understanding vocal learning. The Australian zebra finch (Taeniopygia castanotis) is the most studied model organism for vocal learning. In captivity, juveniles are typically housed with their father, where males learn their father song and females develop a preference for that song. In nature, however, the social structure of zebra finches is more dynamic across space and time. To identify the natural social conditions during song learning, we followed zebra finch families across their early life in the wild using automated radio-tracking. The distance between juveniles and their parents increased post-fledging and became similar to the distance between juveniles and unrelated adults by the second half of the song learning period. These findings indicate a highly dynamic social environment during the song learning period and suggest that juvenile males could learn from many tutors and that females may develop broader song preferences. Thus, studies based on one-tutor paradigms should be interpreted carefully with respect to functional implications and highlight that future vocal learning studies could better reflect the social conditions under which song develops.

animal behavior and cognition↗
bioRxiv2026

Data-driven frame-by-frame analysis of surface swimming and terrestrial walking in the coastal beetle Phaleria atriceps

Background. Inter-leg coordination of insects changes depending on environmental conditions. Although locomotor changes between terrestrial and aquatic environments have been examined in various insects, relatively little is known about coastal insects living at the boundary between these environments. We therefore compared the inter-leg coordination during terrestrial walking with that during surface swimming in the coastal beetle Phaleria atriceps. Methods. Surface swimming was recorded in 17 individuals and terrestrial walking in 10 individuals using high-speed video at 1,000 frames/s. The six leg tips and anterior and posterior body landmarks were tracked frame-by-frame using DeepLabCut, and leg movements were quantified in a body-centered coordinate system. Leg movement periods were estimated from sinusoidal fits to longitudinal leg-tip trajectories. Inter-leg phase relationships were calculated for all 15 leg pairs and integrated to reconstruct a representative six-leg phase organization for each locomotor mode. Results. Leg movement periods were significantly longer during surface swimming than during terrestrial walking for all six legs. During walking, the six-leg phase relationship closely matched an alternating tripod pattern, with a left foreleg (L1), a right middle leg (R2), and a left hind leg (L3) forming one phase group and a right foreleg (R1), a left middle leg (L2), and a right hind leg (R3) forming the opposing group. The same broad grouping was observed in the six-leg phase relationship during surface swimming, although significant differences in relative phase were detected for L1-L2, L1-R2, and R1-R2. Conclusions. Phaleria atriceps exhibited six-leg phase relationships broadly consistent with an alternating tripod pattern during both terrestrial walking and surface swimming, whereas leg movement periods and certain inter-leg phase relationships differed between the two locomotor modes. These findings provide a quantitative description of the similarities and differences in inter-leg coordination between terrestrial walking and surface swimming in a coastal beetle. Further mechanical and comparative studies will be needed to clarify the functional and evolutionary significance of these findings.

animal behavior and cognition↗