Animal Navigation Research Articles

Electromagnetic induction between axons and their schwann cell myelin-protein sheaths

Two concepts have long dominated vertebrate nerve electrophysiology: (a) Schwann cell-formed myelin sheaths separated by minute non-myelinated nodal gaps and spiraling around axons of peripheral motor nerves reduce current leakage during propagation of trains of axon action potentials; (b) "jumping" by action potentials between successive nodes greatly increases signal conduction velocity. Long-held and more recent assumptions and issues underlying those concepts have been obscured by research emphasis on axon-sheath biochemical symbiosis and nerve regeneration. We hypothesize: mutual electromagnetic induction in the axon-glial sheath association, is fundamental in signal conduction in peripheral and central myelinated axons, explains the g-ratio and is relevant to animal navigation.

Place Avoidance Tasks as Tools in the Behavioral Neuroscience of Learning and Memory

Spatial navigation comprises a widely-studied complex of animal behaviors. Its study offers many methodological advantages over other approaches, enabling assessment of a variety of experimental questions and the possibility to compare the results across different species. Spatial navigation in laboratory animals is often considered a model of higher human cognitive functions including declarative memory. Almost fifteen years ago, a novel dry-arena task for rodents was designed in our laboratory, originally named the place avoidance task, and later a modification of this approach was established and called active place avoidance task. It employs a continuously rotating arena, upon which animals are trained to avoid a stable sector defined according to room-frame coordinates. This review describes the development of the place avoidance tasks, evaluates the cognitive processes associated with performance and explores the application of place avoidance in the testing of spatial learning after neuropharmacological, lesion and other experimental manipulations.

Guidance by odors in honeybee navigation

Animal navigation is guided by multiple sensory cues. Here, we ask whether and how olfactory stimuli emanating from places other than the trained feeding site redirect the flight paths of honeybees. The flight trajectories of individual bees were registered using harmonic radar tracking. Sensory cues (compass direction, distance, visual cues en route and close to the feeding site) associated with the trained flight route dominated wayfinding, but a learned odorant carried by air flow induced excursions into the wind. These redirections were largely restricted to rather small deviations from the trained route (<60°, <200m) and occurred only if the animal did not receive the trained odorant stimulus at the trained feeding site. Under certain conditions, larger excursions were observed. These findings are discussed in the context of odor guidance of honeybees over longer distances (>300m from the hive).

Being Humbled by Animal Navigation

Being Humbled by Animal Navigation

Genesis and evolution of polarization of light in the ocean [Invited

The radiative transfer of sunlight through the deep oceans of the world is a complex and only partially solved environmental optical problem. Empirically, in situ systematic measurements of key parameters such as polarization of deep open seawater have been very sparse in recent decades. Although we have the necessary equation of transfer to solve this complex problem, until it can be solved explicitly, only approximations and partial analytic solutions are possible in addition to some successful computer modeling. Further complexity is added by the diversity of researchers' interests from academic to international policy making, as well as the ineffective communication between the different disciplines concerned, ranging from mathematics to endangered species. As a result, isolated focused pockets of good data and theory have been developed in recent decades without the needed breadth of understanding. This present review intends to bring together some visual biology and optical physics in order to understand the role of polarization in navigation, communication, and identification of marine animals as well as a possible tool for remotely sensing underwater objects.

Animal Navigation: Salmon Track Magnetic Variation

How animals navigate long distances to specific targets remains enigmatic. For Pacific salmon, new evidence suggests fish imprint on the magnetic coordinates of their home river and use this information to guide their return from distant open-ocean feeding areas.

Life as a Cataglyphologist—and Beyond

Rüdiger Wehner's lifelong research activities centered on Cataglyphis have rendered these thermophilic desert ants model organisms in the study of animal navigation. The present account describes how the author encountered Cataglyphis and established a study site at Maharès, Tunisia; how he increasingly focused his research on the neuroethological analysis of the ant's navigational toolkit; and finally, how he extended these studies to thermophilic desert ants in other deserts of the world, to Ocymyrmex in southern Africa and Melophorus in central Australia. By including aspects of functional morphology, physiology, and ecology in his research projects, he has favored-and advocated-an organism-centered approach. Beyond "cataglyphology," he was engaged in substantial teaching both at his home university in Zürich and overseas, writing a textbook, running a department, and working as a Permanent Fellow at the Institute for Advanced Study in Berlin.

Radial Bias for Motion – Centrifugal or Centripetal?

Event Abstract Back to Event Radial Bias for Motion – Centrifugal or Centripetal? Ryan T. Maloney1, 2*, Tamara L. Watson3 and Colin W. Clifford1, 2 1 University of Sydney, School of Psychology, Australia 2 Australian Research Council Centre of Excellence in Vision Science, Australia 3 The University of Western Sydney,, School of Social Sciences and Psychology, Australia Background: As an animal moves through the environment complex patterns of image motion stimulate the eyes. These patterns provide important cues in the coordination of navigation and locomotion in humans and other animals. Recent reports indicate that human early visual cortex responds preferentially to motion radial to the point of fixation. Here, we sought to investigate the determinants of this radial bias for motion. Method: In 2 experiments, functional magnetic resonance imaging (fMRI; n = 6 human subjects) at 3T was used to measure blood-oxygenation level-dependent (BOLD) activity in functionally-defined regions of visual cortex to band-pass filtered random dot fields moving along 16 different complex motion trajectories (contracting, expanding, rotating and spiralling fields) centred at the fovea. In the first experiment these were “full-field” dot patterns that simulated optic flow. In the second experiment stimuli were restricted either to an annulus close to the fovea (0.75-1.87 deg) or further in the periphery (4.81-6.28 deg). Eye position and attention were controlled by requiring subjects to monitor a sporadic dimming of the fixation spot. Eye position was also recorded in some subjects using the MR-compatible EyeLink1000 gaze tracking system. Results: Anisotropies were observed in the pattern of BOLD activity dominated by a greater response for contracting or expanding fields. The pattern of these anisotropies changed systematically with eccentricity in visual areas V1-V3, V3A/B and hV4 (but not V5/MT+), evolving from a preference for expanding over contracting patterns close to the fovea, to the exact opposite at the most peripheral region stimulated. This effect was most robust in V2 and V3. In the second experiment, there was again a general preference for radial motions (contracting/expanding), though this did not differ with eccentricity. Discussion: Characteristic processing anisotropies for complex motions exist in human early visual cortex, but their strength and direction depend upon eccentricity when presented full-field. The results suggest that the visual cortex dynamically adjusts its activity in response to moving stimuli depending on the trajectory they are describing on the retina. This may reflect the predictability of the stimulus motion, which is known to have a significant influence on both perceptual variables and visual cortical activity. Acknowledgements Funding: This work was supported by a National Health and Medical Research Council grant (C.W.G.C.; grant number APP1027258), an Australian Research Council (ARC) Future Fellowship (C.W.G.C.; grant number FT110100150), an ARC Post-doctoral Fellowship (T.L.W.; grant number DP11010217) and the ARC Centre of Excellence in Vision Science. The authors thank Dr Isabelle Mareschal and Dr Sam Solomon for helpful discussions and Kirsten Moffatt and the MRI radiography team at St. Vincent's hospital. Keywords: Complex motion perception, Early Visual Cortex, fMRI, Optic Flow, radial bias Conference: ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013. Presentation Type: Poster Topic: Sensation and Perception Citation: Maloney RT, Watson TL and Clifford CW (2013). Radial Bias for Motion – Centrifugal or Centripetal?. Conference Abstract: ACNS-2013 Australasian Cognitive Neuroscience Society Conference. doi: 10.3389/conf.fnhum.2013.212.00039 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 15 Oct 2013; Published Online: 25 Nov 2013. * Correspondence: Dr. Ryan T Maloney, University of Sydney, School of Psychology, Sydney, Australia, ryan.maloney@sydney.edu.au Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Ryan T Maloney Tamara L Watson Colin W Clifford Google Ryan T Maloney Tamara L Watson Colin W Clifford Google Scholar Ryan T Maloney Tamara L Watson Colin W Clifford PubMed Ryan T Maloney Tamara L Watson Colin W Clifford Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

MonarchBase: the monarch butterfly genome database

The monarch butterfly (Danaus plexippus) is emerging as a model organism to study the mechanisms of circadian clocks and animal navigation, and the genetic underpinnings of long-distance migration. The initial assembly of the monarch genome was released in 2011, and the biological interpretation of the genome focused on the butterfly’s migration biology. To make the extensive data associated with the genome accessible to the general biological and lepidopteran communities, we established MonarchBase (available at http://monarchbase.umassmed.edu). The database is an open-access, web-available portal that integrates all available data associated with the monarch butterfly genome. Moreover, MonarchBase provides access to an updated version of genome assembly (v3) upon which all data integration is based. These include genes with systematic annotation, as well as other molecular resources, such as brain expressed sequence tags, migration expression profiles and microRNAs. MonarchBase utilizes a variety of retrieving methods to access data conveniently and for integrating biological interpretations.

Nature's compass: the mystery of animal navigation

The mysterious and remarkable ways that animals navigate We know that animals cross miles of water, land, and sky with pinpoint precision on a daily basis. But it is only in recent years that scientists have learned how these astounding feats of navigation are actually accomplished. With colorful and thorough detail, Nature's Compass explores the remarkable methods by which animals find their way both near home and around the globe. Noted biologist James Gould and popular science writer Carol Gould delve into the elegant strategies and fail-safe backup systems, the invisible sensitivities and mysterious forces, and incredible mental abilities used by familiar and rare species, as they investigate a multitude of navigation strategies, from the simple to the astonishing. The Goulds discuss how animals navigate, without instruments and training, at a level far beyond human talents. They explain how animals measure time and show how the fragile monarch butterfly employs an internal clock, calendar, compass, and map to commence and measure the two-thousand-mile annual journey to Mexico—all with a brain that weighs only a few thousandths of an ounce. They look at honey bees and how they rely on the sun and mental maps to locate landmarks such as nests and flowers. And they examine whether long-distance migrants, such as the homing pigeon, depend on a global positioning system to let them know where they are. Ultimately, the authors ask if the disruption of migratory paths through habitat destruction and global warming is affecting and endangering animal species. Providing a comprehensive picture of animal navigation and migration, Nature's Compass decodes the mysteries of this extraordinary aspect of natural behavior.

Bio-inspired polarized skylight-based navigation sensors: a review.

Animal senses cover a broad range of signal types and signal bandwidths and have inspired various sensors and bioinstrumentation devices for biological and medical applications. Insects, such as desert ants and honeybees, for example, utilize polarized skylight pattern-based information in their navigation activities. They reliably return to their nests and hives from places many kilometers away. The insect navigation system involves the dorsal rim area in their compound eyes and the corresponding polarization sensitive neurons in the brain. The dorsal rim area is equipped with photoreceptors, which have orthogonally arranged small hair-like structures termed microvilli. These are the specialized sensors for the detection of polarized skylight patterns (e-vector orientation). Various research groups have been working on the development of novel navigation systems inspired by polarized skylight-based navigation in animals. Their major contributions are critically reviewed. One focus of current research activities is on imitating the integration path mechanism in desert ants. The potential for simple, high performance miniaturized bioinstrumentation that can assist people in navigation will be explored.

Maintaining a Cognitive Map in Darkness: The Need to Fuse Boundary Knowledge with Path Integration

Spatial navigation requires the processing of complex, disparate and often ambiguous sensory data. The neurocomputations underpinning this vital ability remain poorly understood. Controversy remains as to whether multimodal sensory information must be combined into a unified representation, consistent with Tolman's “cognitive map”, or whether differential activation of independent navigation modules suffice to explain observed navigation behaviour. Here we demonstrate that key neural correlates of spatial navigation in darkness cannot be explained if the path integration system acted independently of boundary (landmark) information. In vivo recordings demonstrate that the rodent head direction (HD) system becomes unstable within three minutes without vision. In contrast, rodents maintain stable place fields and grid fields for over half an hour without vision. Using a simple HD error model, we show analytically that idiothetic path integration (iPI) alone cannot be used to maintain any stable place representation beyond two to three minutes. We then use a measure of place stability based on information theoretic principles to prove that featureless boundaries alone cannot be used to improve localization above chance level. Having shown that neither iPI nor boundaries alone are sufficient, we then address the question of whether their combination is sufficient and – we conjecture – necessary to maintain place stability for prolonged periods without vision. We addressed this question in simulations and robot experiments using a navigation model comprising of a particle filter and boundary map. The model replicates published experimental results on place field and grid field stability without vision, and makes testable predictions including place field splitting and grid field rescaling if the true arena geometry differs from the acquired boundary map. We discuss our findings in light of current theories of animal navigation and neuronal computation, and elaborate on their implications and significance for the design, analysis and interpretation of experiments.

Where on earth can animals use a geomagnetic bi‐coordinate map for navigation?

Many animal taxa have been shown to possess the ability of true navigation. In this study we investigated the possibilities for geomagnetic bi‐coordinate map navigation in different regions of the earth by analysing angular differences between isolines of geomagnetic total intensity and inclination. In ‘no‐grid’ zones where isolines were running almost parallel, efficient geomagnetic bi‐coordinate navigation would probably not be feasible. These zones formed four distinct areas with a north‐south extension in the northern hemisphere, whereas the pattern in the southern hemisphere was more diffuse. On each side of these zones there was often a mirror effect where identical combinations of the geomagnetic parameters appeared. This may potentially cause problems for species migrating long distances east‐west across longitudes, since they may pass areas with identical geomagnetic coordinates. Migration routes assumed for four populations of migratory passerine birds were used to illustrate the possibilities of geomagnetic bi‐coordinate map navigation along different routes. We conclude that it is unlikely that animal navigation is universally based on a geomagnetic bi‐coordinate map mechanism only, and we predict that the relative importance of geomagnetic coordinate information differs between animals, areas and routes, depending on the different conditions for bi‐coordinate geomagnetic navigation in different regions of the earth.

Consistent effect of an attached magnet on the initial orientation of homing pigeons, Columba livia

There is ongoing debate about which sensory mechanisms are critical for animal navigation over long distances. We tested whether magnetoreception associated with the front of the head is involved in navigation by homing pigeons. We attached small, but strong, rare-earth magnets atop the ceres of experienced homing pigeons and released the birds under sunny conditions. In releases distributed over a wide range of distances and directions, the mean vanishing directions of birds carrying magnets were consistently (91% of releases) shifted to the right of controls carrying brass weights. The right shift appeared within a few minutes after release and was reproducible over consecutive years. The magnet's effect was sustained (82%) in birds released repeatedly at one site and was larger (73%) for a North-up than for a South-up orientation of the magnet in releases (88%), where the North-up and South-up groups of experimental birds were right-shifted relative to their controls. We discuss several possible nonnavigational and navigational explanations for the magnet's effect on the pigeons' vanishing direction.

Distinguishing Social from Nonsocial Navigation in Moving Animal Groups

Many animals, such as migrating shoals of fish, navigate in groups. Knowing the mechanisms involved in animal navigation is important when it comes to explaining navigation accuracy, dispersal patterns, population and evolutionary dynamics, and consequently, the design of conservation strategies. When navigating toward a common target, animals could interact socially by sharing available information directly or indirectly, or each individual could navigate by itself and aggregations may not disperse because all animals are moving toward the same target. Here we present an analysis technique that uses individual movement trajectories to determine the extent to which individuals in navigating groups interact socially, given knowledge of their target. The basic idea of our approach is that the movement directions of individuals arise from a combination of responses to the environment and to other individuals. We estimate the relative importance of these responses, distinguishing between social and nonsocial interactions. We develop and test our method, using simulated groups, and we demonstrate its applicability to empirical data in a case study on groups of guppies moving toward shelter in a tank. Our approach is generic and can be extended to different scenarios of animal group movement.

Controlling airborne cues to study small animal navigation

Small animals such as nematodes and insects analyze airborne chemical cues to infer the direction of favorable and noxious locations. In these animals, the study of navigational behavior evoked by airborne cues has been limited by the difficulty of precisely controlling stimuli. We present a system that can be used to deliver gaseous stimuli in defined spatial and temporal patterns to freely moving small animals. We used this apparatus, in combination with machine-vision algorithms, to assess and quantify navigational decision making of Drosophila melanogaster larvae in response to ethyl acetate (a volatile attractant) and carbon dioxide (a gaseous repellant).

Re-Visiting of Plentiful Food Sources and Food Search Strategies in Desert Ants

North African desert ants, Cataglyphis fortis, are established model organisms in animal navigation research. Cataglyphis re-visit plentiful feeding sites, but their decision to return to a feeder and the organization of food searches has been little studied. Here we provide a review of recent advances regarding this topic. At least two parameters determine the ants’ assessment of site quality, namely, amount of food available and reliability of food encounter on subsequent visits. The amount of food appears to be judged by the concentration of items at the food uptake site. Initially the amount of food in a feeder dominates the foragers’ decision to return, whereas learning about reliability takes precedence in the course of a few visits. The location of a worthwhile site is determined by the animals’ path integration system. In particular, the distance of the feeding site is memorized as the arithmetic average of the distances covered during the previous outbound and homebound journeys. Feeding sites that are small and inconspicuous cannot be approached directly with sufficient certainty, due to inevitable inaccuracies of the path integrator. Instead, desert ants steer downwind of the goal to encounter the odor plume emanating from the food and they follow this plume to the feeder. The angle steered downwind reflects the animals’ maximal navigation error and is adjusted according to experience. In summary, food searches of desert ants provide an unexpected wealth of features that may advance our understanding of search, navigation, and decision strategies. There are several aspects that warrant further scrutiny.

Initial evidence of path integration in desert sand scorpions.

Initial evidence of path integration in desert sand scorpions.

Lunar skylight polarization signal polluted by urban lighting

[1] On clear moonlit nights, a band of highly polarized light stretches across the sky at a 90 degree angle from the moon, and it was recently demonstrated that nocturnal organisms are able to navigate based on it. Urban skyglow is believed to be almost unpolarized, and is therefore expected to dilute this unique partially linearly polarized signal. We found that urban skyglow has a greater than expected degree of linear polarization (p = 8.6 ± 0.3%), and confirmed that its presence diminishes the natural lunar polarization signal. We also observed that the degree of linear polarization can be reduced as the moon rises, due to the misalignment between the polarization angles of the skyglow and scattered moonlight. Under near ideal observing conditions, we found that the lunar polarization signal was clearly visible (p = 29.2 ± 0.8%) at a site with minimal light pollution 28 km from Berlin's center, but was reduced (p = 11.3 ± 0.3%) within the city itself. Daytime measurements indicate that without skyglow pwould likely be in excess of 50%. These results indicate that nocturnal animal navigation systems based on perceiving polarized scattered moonlight likely fail to operate properly in highly light-polluted areas, and that future light pollution models must take polarization into account.

Migratory navigation in birds: new opportunities in an era of fast-developing tracking technology

Birds have remained the dominant model for studying the mechanisms of animal navigation for decades, with much of what has been discovered coming from laboratory studies or model systems. The miniaturisation of tracking technology in recent years now promises opportunities for studying navigation during migration itself (migratory navigation) on an unprecedented scale. Even if migration tracking studies are principally being designed for other purposes, we argue that attention to salient environmental variables during the design or analysis of a study may enable a host of navigational questions to be addressed, greatly enriching the field. We explore candidate variables in the form of a series of contrasts (e.g. land vs ocean or night vs day migration), which may vary naturally between migratory species, populations or even within the life span of a migrating individual. We discuss how these contrasts might help address questions of sensory mechanisms, spatiotemporal representational strategies and adaptive variation in navigational ability. We suggest that this comparative approach may help enrich our knowledge about the natural history of migratory navigation in birds.