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Evidence for a magnetic map in juvenile green turtles. a A juvenile green turtle swimming in a magnetic navigation experiment. Turtles were placed into soft cloth harnesses and tethered to an electronic tracking device that monitored their orientation as they swam in a water-filled arena surrounded by a magnetic coil system. b Juvenile turtles were captured in feeding grounds near the test site in Florida. Each turtle was exposed to a magnetic field that exists at one of two distant locations along the coastline (represented by the blue dots). Turtles exposed to the field from the northern site swam approximately southward, whereas those exposed to the field from the southern site swam approximately northward. In the orientation diagrams, each dot represents the mean angle of a single turtle. The arrow in the center of each circle represents the mean angle of the group. Dashed lines represent the 95% confidence interval for the mean angle. Map scale bar is 100 km. Figure modified from Lohmann et al. (2004)
Source publication
In addition to providing animals with a source of directional or ‘compass’ information, Earth’s magnetic field also provides a potential source of positional or ‘map’ information that animals might exploit to assess location. In less than a generation, the idea that animals use Earth’s magnetic field as a kind of map has gone from a contentious hyp...
Citations
... Despite decades of research, the mechanisms and environmental cues guiding long-distance migratory birds continue to be a subject of ongoing scientific inquiry (Hagstrum, 2023;Lohmann et al., 2022;Mouritsen, 2018;Wallraff, 2004). This is particularly true for the process of true navigation, where birds utilise local information to navigate towards distant targets (Holland, 2014). ...
... This model suggests that birds employ two distinct mechanisms: a map sense to determine their position relative to their destination (geographic positioning) and a compass sense to determine a desired heading (compass orientation). Within the map and compass framework, the Earth's magnetic field has been proposed as a potential source of both map and compass information (Lohmann et al., 2022). Nonetheless, researchers continue to debate whether geomagnetic cues alone are sufficient for the "map" sense or whether additional mechanisms-such as olfactory navigation (Bonadonna and Gagliardo, 2021;Gagliardo et al., 2021;Wallraff, 2004;Wallraff, 2005), infrasound (Hagstrum, 2000;Hagstrum, 2013;Patrick et al., 2021), or celestial compasses (Alerstam et al., 2001;Muheim et al., 2006)-are essential. ...
... To compensate, they must recalibrate their orientation by referencing a "map" sense, which may be geomagnetic, olfactory, or even infrasound-based (Chernetsov et al., 2008;Gagliardo et al., 2011;Hagstrum, 2000;Holland, 2014). While the map sense's exact mechanism remains contentious (Bonadonna and Gagliardo, 2021;Hagstrum, 2023;Wallraff, 2004;Wiltschko and Wiltschko, 2017), geomagnetic gradients-such as latitudinal variations in inclination and intensity-are hypothesised to provide birds with a positional framework (Dennis et al., 2007;Kishkinev et al., 2013;Lohmann et al., 2022;Wiltschko and Wiltschko, 2023). For a more detailed discussion of these debates, see the reviews by Able (2001) and Demšar et al. (2025). ...
... Unsurprisingly, both light and geomagnetic fields are quantum phenomena! It is now known that a wide range of animals, from birds to lobsters, utilize magnetic positional information for various reasons, including navigating towards specific objectives, adjusting food intake at strategic times during migration, staying within a suitable oceanic region, and maintaining course along migratory pathways [3]. ...
... The notion that animals use the Earth's magnetic field as a sort of map has evolved from a controversial theory to a widely accepted principle of animal navigation in less than a generation. It is now known that a wide range of animals, from birds to lobsters, use magnetic positional information for several reasons, such as navigating towards particular objectives, modifying food intake at strategic points during a migration, staying within an appropriate oceanic region, and staying on course along migratory pathways [3]. ...
Quantum computing applications in diverse domains are emerging rapidly. Given the limitations of classical computing techniques, the peculiarity of quantum circuits, which can observe quantum phenomena such as superposition, entanglement, and quantum coherence, is remarkable. This capability enables them to achieve measurement sensitivities far beyond classical limits. Research on radical pair-based magnetoreception in migratory birds has been a focus area for quite some time. A quantum mechanics-based computing approach, thus unsurprisingly, identifies a scope of application. In this study, to observe the phenomenon, electron-nucleus spin quantum circuits for different geomagnetic fluxes have been simulated and run through IBM Qiskit quantum processing units with error mitigation techniques. The results of different quantum states are consistent, suggesting singlet-triplet mechanisms that can be emulated, resembling the environment-enabling flights of migratory birds through generations of the avian species. The four-qubit model emulating electron-nucleus systems mimicking the environmental complexity outcome shows the sensitiveness to change of magnetic flux index, high probability of singlet-triplet dynamics, and upholding radical pair model states by the purity of the sub-system and full system outcome of coherence, the hallmark of singlet state dominance. The work involved performing fifty quantum circuits for different magnetic field values, each with one thousand and twenty-four shots for measurement, either in the simulator or on real quantum hardware, and for two error mitigation techniques, preceded by a noise model of a simulator run.
... Accordingly, some animals can exploit the magnetic field for directional reference (i.e. maintain headings) and some animals are apparently able to get positional information from the magnetic field (i.e. a magnetic map) (Johnsen et al., 2020;Lohmann et al., 2022). Further, the magnetic inclination also allows a vertical reference when other environmental cues, such as celestial or gravitational cues, are obstructed or unavailable (e.g. ...
Whereas science is written by humans and cannot escape emotions intervening with scientific thought, the scientific community should be on guard against unnoticeably adopting a favorite hypothesis. When adopting a favorite hypothesis, scientists tend to review their work in favor of this hypothesis and reject contradictory data. In 1890, Thomas Chrowder Chamberlin first described this phenomenon as when ‘the search for facts, and their interpretation are dominated by affection for the favored theory until it appears to its advocate to have been overwhelmingly established’. The favorite hypothesis can then quickly transition into a ruling hypothesis, leading to an unconscious bias in favor of supporting evidence and neglect of contradictory observations. This is especially problematic when a scientific field adopts a favorite hypothesis. In this Commentary, we suggest that the field of animal magnetoreception – in particular mechanisms based on radical-pair chemistry and cryptochrome proteins – may be under the reign of a ruling hypothesis. We argue that repeatedly, conclusions are unfounded or otherwise not consistent with the results presented. We use the case of magnetoreception – the only sense that remains without a clearly described receptor – to raise general awareness of the phenomenon of a ruling hypothesis in the scientific community. We emphasize the distinction between the scientist and the scientific community suffering from a hypothesis regime, and further highlight suggestions to mitigate the risk of working under a ruling hypothesis.
... This route may mimic the path turtles took as hatchlings when they dispersed from their natal beaches for the first time and were swept out into ocean currents [64]. This idea may shed light on how they initially found their adult foraging habitats, since there is ample experimental and observational evidence demonstrating the ability of sea turtles to detect and orient to magnetic fields throughout their pelagic [65][66][67], neritic [68,69], and adult [70,71] stages. Nevertheless, more research on this aspect of foraging-ground finding is needed. ...
The hawksbill turtle, Eretmochelys imbricata, has been at risk of extinction for more than 40 years and remains critically endangered. While nesting beach protection is important for hatchling production, identifying inter-nesting, migratory, and foraging habitats is crucial for mitigating threats to population recovery. We report the use of satellite telemetry to monitor movements of 15 hawksbill turtles in the Western Caribbean. Transmitters were deployed on nesting turtles in Honduras (2012 n = 2; 2017 n = 3), Costa Rica (2000 n = 2; 2014 n = 1; 2015 n = 1; 2018 n = 4; 2021 n = 1), and Panama (2017 n = 1). Hawksbill inter-nesting habitats ranged from 4-2,643 km² (core 50% utilization distribution) for the 15–70 tracking days. Large inter-nesting area use may be a result of habitats adjacent to a narrow continental shelf with strong ocean currents, causing turtles to actively search for suitable habitats. Following nesting, these turtles engaged in migrations to foraging grounds that covered 73–1,059 km lasting between 5–45 days. During migrations, turtles regularly altered their direction relative to ocean currents, using with-current movement to counteract against-current movement. Hawksbills from multiple beaches congregated in the same foraging habitat, despite nesting in different years. Turtles in this study foraged along the coastal and continental shelves of Nicaragua, Honduras, Belize, and Mexico, with turtles from disparate nesting sites utilizing the Nicaragua Rise hotspot area. Foraging area use was generally smaller (n = 8, 6–705 km²) than inter-nesting area use, possibly indicating that foraging habitats provided necessary food and resting areas. These data help us better understand inter-nesting and foraging habitat locations, core area use, and post-nesting migrations. Together, this provides vital information to mitigate potential in-water threats to critically endangered adult hawksbills along Western Caribbean migration corridors.
... Diverse animals migrate immense distances between specific areas used in foraging, reproduction and seasonal sheltering 7-9 . How long-distance migrant animals navigate to specific locations has remained enigmatic, but the ability to exploit the magnetic field of the Earth as a source of both directional information (that is, for a magnetic compass sense) and positional information (that is, for a magnetic map sense) is an important element in the navigational repertoire of many species 1,8,10 . ...
Growing evidence indicates that migratory animals exploit the magnetic field of the Earth for navigation, both as a compass to determine direction and as a map to determine geographical position¹. It has long been proposed that, to navigate using a magnetic map, animals must learn the magnetic coordinates of the destination2,3, yet the pivotal hypothesis that animals can learn magnetic signatures of geographical areas has, to our knowledge, yet to be tested. Here we report that an iconic navigating species, the loggerhead turtle (Caretta caretta), can learn such information. When fed repeatedly in magnetic fields replicating those that exist in particular oceanic locations, juvenile turtles learned to distinguish magnetic fields in which they encountered food from magnetic fields that exist elsewhere, an ability that might underlie foraging site fidelity. Conditioned responses in this new magnetic map assay were unaffected by radiofrequency oscillating magnetic fields, a treatment expected to disrupt radical-pair-based chemical magnetoreception4, 5–6, suggesting that the magnetic map sense of the turtle does not rely on this mechanism. By contrast, orientation behaviour that required use of the magnetic compass was disrupted by radiofrequency oscillating magnetic fields. The findings provide evidence that two different mechanisms of magnetoreception underlie the magnetic map and magnetic compass in sea turtles.
... The magnitude of the geomagnetic field changes by about 3 nT/km in the north-south direction [6], thus over 50 km the change will be δB ≈ 0.15 µT. The authors in Ref. [135] mention that magnetic anomalies of Earth's field, known to be mostly at the level of 1%, could offer navigational cues. This argument would imply δB = 0.45 µT. ...
A large number of magnetic sensors, like superconducting quantum interference devices, optical pumping, and nitrogen vacancy magnetometers, were shown to satisfy the energy resolution limit. This limit states that the magnetic sensitivity of the sensor, when translated into a product of energy with time, is bounded below by Planck's constant, ℏ . This bound implies a fundamental limitation as to what can be achieved in magnetic sensing. Here we explore biological magnetometers, in particular three magnetoreception mechanisms thought to underly animals' geomagnetic field sensing: the radical-pair, the magnetite, and the MagR mechanism. We address the question of how close these mechanisms approach the energy resolution limit. At the quantitative level, the utility of the energy resolution limit is that it informs the workings of magnetic sensing in model-independent ways and thus can provide subtle consistency checks for theoretical models and estimated or measured parameter values, particularly needed in complex biological systems. At the qualitative level, the closer the energy resolution is to ℏ , the more “quantum” is the sensor. This offers an alternative route towards understanding the quantum biology of magnetoreception. It also quantifies the room for improvement, illuminating what nature has achieved, and stimulating the engineering of biomimetic sensors exceeding nature's magnetic sensing performance.
Published by the American Physical Society 2025
... In social migrants (e, f), by contrast, route innovations can be transferred between generations if F2 individuals follow returning F1 innovators on return migrations, regardless of whether the initial innovation mechanism was stochastic e or endogenous f movements or changes in migratory movements) can plausibly be successfully colonized in the absence of heritable changes in migratory programmes, provided that future offspring exhibit natal philopatry (as is typical in migratory species [24]) and their existing migratory programmes still carry them to viable non-breeding areas. In effect, offspring need only return to their previously experienced natal location (e.g., via 'magnetic maps' [53]), whereas reaching a novel non-breeding location can require mechanisms of information transfer between generations (i.e., heritable changes in genetic programme or social learning). However, it is notable that Madsen et al. [55] recently documented social information being an important key driver of rapid colonisation of new breeding ranges in an Arctic-breeding goose, suggesting that flocking can help facilitate breeding range-shifts in some cases. ...
Background
Many species are exhibiting range shifts associated with anthropogenic change. For migratory species, colonisation of new areas can require novel migratory programmes that facilitate navigation between independently-shifting seasonal ranges. Therefore, in some cases range-shifts may be limited by the capacity for novel migratory programmes to be transferred between generations, which can be genetically and socially mediated.
Methods
Here we used 50 years of North American Breeding Bird Survey and Audubon Christmas Bird Count data to test the prediction that breeding and/or non-breeding range-shifts are more prevalent among flocking migrants, which possess a capacity for rapid social transmission of novel migration routes.
Results
Across 122 North American bird species, social migration was a significant positive predictor for the magnitude of non-breeding centre of abundance (COA) shift within our study region (conterminous United States and Southern Canada). Across a subset of 81 species where age-structured flocking was determined, migrating in mixed-age flocks produced the greatest shifts and solo migrants the lowest. Flocking was not a significant predictor of breeding COA shifts, which were better explained by absolute population trends and migration distance.
Conclusions
Our results suggest that social grouping may play an important role in facilitating non-breeding distributional responses to climate change in migratory species. We highlight the need to gain a better understanding of migratory programme inheritance, and how this influences spatiotemporal population dynamics under environmental change.
... Many animals, from honeybees and salmon to migratory birds, utilize geomagnetic field for navigation (30). However, little is known about the effects of geomagnetic field on the evolution of neurons. ...
Previously, we developed a dynamic magnetic field (DMF) device using neodymium magnets that induced c-fos expression in cortical neurons, while activity-regulated cytoskeleton-associated protein (Arc), and brain-derived neurotrophic factor (BDNF) remained unaffected. The precise signal transduction pathway for c-fos induction under DMF was unclear. This study aimed to investigate the mechanism of immediate early gene (IEG) induction using calcium channel blockers (CCBs). Six experiments were conducted with cortical neurons, employing an NMDA receptor antagonist and an L-type voltage-dependent calcium channel blocker as CCBs. Neuronal cultures were exposed to DMF, CCBs, or both, and IEG expression (Arc, c-fos, BDNF) was measured through polymerase chain reaction. Results showed a tendency for increased c-fos expression with DMF exposure, which was unaffected by CCBs. In contrast, Arc and BDNF were not induced under DMF exposure but were significantly inhibited by CCBs. These findings suggest that c-fos induction under DMF involves a distinct pathway, potentially relevant to stress resistance and drug discovery.
... Many animals have homing abilities on the order of meters to thousands of kilometers (Able, 1980). The proximate causations underlying these remarkable feats of navigation are as diverse as the taxa that employ them, ranging from celestial rotation (Emlen, 1970) to patterns of polarized light (von Frisch, 1993) to changes in the geomagnetic field (Lohmann et al., 2022). Likewise, the ultimate causation of these extraordinary feats of navigation are known to increase survival and reproduction through energy conservation (Weber, 2009), avoidance of disturbance (Mikula et al., 2018), successful return to productive feeding grounds (Acevedo et al., 2022), mating aggregations (Dittman and Quinn, 1996), or nesting sites (Scott et al., 2014). ...
... The authors in [135] mention that magnetic anomalies of earth's field, known to be mostly at the level of 1%, could offer navigational cues. This argument would imply δB = 0.45¯T. ...
A large number of magnetic sensors, like superconducting quantum interference devices, optical pumping and nitrogen vacancy magnetometers, were shown to satisfy the energy resolution limit. This limit states that the magnetic sensitivity of the sensor, when translated into a product of energy with time, is bounded below by Planck’s constant, ħ. This bound implies a fundamental limitation as to what can be achieved in magnetic sensing. Here we explore biological magnetometers, in particular three magnetoreception mechanisms thought to underly animals’ geomagnetic field sensing: the radical-pair, the magnetite and the MagR mechanism. We address the question of how close these mechanisms approach the energy resolution limit. At the quantitative level, the utility of the energy resolution limit is that it informs the workings of magnetic sensing in model-independent ways, and thus can provide subtle consistency checks for theoretical models and estimated or measured parameter values, particularly needed in complex biological systems. At the qualitative level, the closer the energy resolution is to ħ, the more “quantum” is the sensor. This offers an alternative route towards understanding the quantum biology of magnetoreception. It also quantifies the room for improvement, illuminating what Nature has achieved, and stimulating the engineering of biomimetic sensors exceeding Nature’s magnetic sensing performance.
