Evidence for the use of magnetic map information by an amphibian

During long-distance migrations, animals navigate using a variety of sensory cues, mechanisms and strategies. Although guidance mechanisms are usually studied under controlled laboratory conditions, such methods seldom allow for navigation behavior to be examined in an environmental context. Similarly, although realistic environmental models are often used to investigate the ecological implications of animal movement, explicit consideration of navigation mechanisms in such models is rare. Here, we used an interdisciplinary approach in which we first conducted lab-based experiments to determine how hatchling loggerhead sea turtles (Caretta caretta) respond to magnetic fields that exist at five widely separated locations along their migratory route, and then studied the consequences of the observed behavior by simulating it within an ocean circulation model. Magnetic fields associated with two geographic regions that pose risks to young turtles (due to cold wintertime temperatures or potential displacement from the migratory route) elicited oriented swimming, whereas fields from three locations where surface currents and temperature pose no such risk did not. Additionally, at locations with fields that elicited oriented swimming, simulations indicate that the observed behavior greatly increases the likelihood of turtles advancing along the migratory pathway. Our findings suggest that the magnetic navigation behavior of sea turtles is intimately tied to their oceanic ecology and is shaped by a complex interplay between ocean circulation and geomagnetic dynamics.

Section: Orientation Experimentsmentioning

confidence: 99%

Magnetic navigation behavior and the oceanic ecology of young loggerhead sea turtles

Putman

Verley

Endres

et al. 2015

“…For example, it been suggested that newts, which generally move over relatively short distances of only a few kilometers during homing (e.g. Fischer et al, 2001;Phillips et al, 2002), use magnetic inclination to determine latitude. More impressive, several studies have also indicated that inclination has an important role in Conditioned discrimination of magnetic inclination in a spatialorientation arena task by homing pigeons (Columba livia) Cordula V. Mora*, Merissa L. Acerbi and Verner P. Bingman position determination for marine long-distance migrators.…”

Section: Research Articlementioning

confidence: 99%

Conditioned discrimination of magnetic inclination in a spatial-orientation arena task by homing pigeons (Columba livia)

Mora

Acerbi

Bingman

2014

It has been well established that homing pigeons are able to use the Earth's magnetic field to obtain directional information when returning to their loft and that their magnetic compass is based, at least in part, on the perception of magnetic inclination. Magnetic inclination has also been hypothesized in pigeons and other long-distance navigators, such as sea turtles, to play a role providing positional information as part of a map. Here we developed a behavioral paradigm which allows us to condition homing pigeons to discriminate magnetic inclination cues in a spatial-orientation arena task. Six homing pigeons were required to discriminate in a circular arena between feeders located either in a zone with a close to 0 deg inclination cue or in a zone with a rapidly changing inclination cue (−3 deg to +85 deg when approaching the feeder and +85 deg to −3 deg when moving away from the feeder) to obtain a food reward. The pigeons consistently performed this task above chance level. Control experiments, during which the coils were turned off or the current was running anti-parallel through the double-wound coil system, confirmed that no alternative cues were used by the birds in the discrimination task. The results show that homing pigeons can be conditioned to discriminate differences in magnetic field inclination, enabling investigation into the peripheral and central neural processing of geomagnetic inclination under controlled laboratory conditions.

“…Red-spotted newts Notophthalmus viridescens exposed to a magnetic field with an intensity matching that of the home area but an inclination angle found to the north oriented southward, whereas those exposed to an inclination angle found south of their area walked northward (Fischer et al, 2001;Phillips et al, 2002). Thus newts, like sea turtles (Lohmann and Lohmann, 1994), can distinguish among different magnetic inclination angles.…”

Section: Magnetic Maps and Target Areasmentioning

confidence: 99%

Magnetic maps in animals: nature's GPS

Lohmann

Putman

2007

217

214

SUMMARY Diverse animals detect the Earth's magnetic field and use it as a cue in orientation and navigation. Most research on magnetoreception has focused on the directional or `compass' information that can be extracted from the Earth's field. Because the field varies predictably across the surface of the globe, however, it also provides a potential source of positional or `map'information, which some animals use to steer themselves along migratory pathways or to navigate toward specific target areas. The use of magnetic positional information has been demonstrated in several diverse animals including sea turtles, spiny lobsters, newts and birds, suggesting that such systems are phylogenetically widespread and can function over a wide range of spatial scales. These `magnetic maps' have not yet been fully characterized. They may be organized in several fundamentally different ways, some of which bear little resemblance to human maps, and they may also be used in conjunction with unconventional navigational strategies.