Magnetic maps in animal navigation.

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 hypothesis to a well-established tenet of animal navigation. Diverse animals ranging from lobsters to birds are now known to use magnetic positional information for a variety of purposes, including staying on track along migratory pathways, adjusting food intake at appropriate points in a migration, remaining within a suitable oceanic region, and navigating toward specific goals.

LACTIC ACIDOSIS INDUCED BY MANUAL RESTRAINT FOR HEALTH EVALUATION AND COMPARISON OF TWO POINT-OF-CARE ANALYZERS IN HEALTHY LOGGERHEAD SEA TURTLES ().

Sea turtles are often restrained manually for brief periods during veterinary evaluation and care in rescue, rehabilitation, research, and aquarium settings. Blood gas values and lactate are routinely evaluated during triage of sea turtles, and lactate clearance is of prognostic significance in cold-stunned individuals. Although increases in blood lactate have been associated with muscle exertion, experimental forced submergence, trawl and pound net capture, and general anesthesia, changes in blood lactate associated with short periods of manual restraint have not been evaluated.

Long-distance transequatorial navigation using sequential measurements of magnetic inclination angle.

Diverse taxa use Earth's magnetic field in combination with other sensory modalities to accomplish navigation tasks ranging from local homing to long-distance migration across continents and ocean basins. Several animals have the ability to use the inclination or tilt of magnetic field lines as a component of a magnetic compass sense that can be used to maintain migratory headings. In addition, a few animals are able to distinguish among different inclination angles and, in effect, exploit inclination as a surrogate for latitude.

Effective mydriasis in juvenile loggerhead turtles (Caretta caretta) following topical administration of rocuronium bromide and 10% phenylephrine.

Objective: To determine the combined mydriatic effects of topical rocuronium bromide and phenylephrine in juvenile loggerhead turtles and identify any adverse effects associated with treatment.

Animals Studied: Eleven juvenile loggerhead turtles (Caretta caretta).

Procedures: Four 20 μL drops of rocuronium bromide and four 20 μL drops of 10% phenylephrine were placed into the right eye at 2-minute intervals of 5 turtles, while the same volume of saline was administered to six control turtles.

There and back again: natal homing by magnetic navigation in sea turtles and salmon.

Diverse marine animals migrate across vast expanses of seemingly featureless ocean before returning as adults to reproduce in the area where they originated. How animals accomplish such feats of natal homing is an enduring mystery. Growing evidence suggests, however, that sea turtles and salmon imprint on the magnetic field of their home area when young and then use this information to return as adults.

Multi-Modal Homing in Sea Turtles: Modeling Dual Use of Geomagnetic and Chemical Cues in Island-Finding.

Sea turtles are capable of navigating across large expanses of ocean to arrive at remote islands for nesting, but how they do so has remained enigmatic. An interesting example involves green turtles (Chelonia mydas) that nest on Ascension Island, a tiny land mass located approximately 2000 km from the turtles' foraging grounds along the coast of Brazil. Sensory cues that turtles are known to detect, and which might hypothetically be used to help locate Ascension Island, include the geomagnetic field, airborne odorants, and waterborne odorants.

The magnetic map of hatchling loggerhead sea turtles.

Young loggerhead sea turtles (Caretta caretta) from eastern Florida, U.S.A.

Longitude perception and bicoordinate magnetic maps in sea turtles.

Long-distance animal migrants often navigate in ways that imply an awareness of both latitude and longitude. Although several species are known to use magnetic cues as a surrogate for latitude, it is not known how any animal perceives longitude. Magnetic parameters appear to be unpromising as longitudinal markers because they typically vary more in a north-south rather than an east-west direction.

Geomagnetic imprinting: A unifying hypothesis of long-distance natal homing in salmon and sea turtles.

Several marine animals, including salmon and sea turtles, disperse across vast expanses of ocean before returning as adults to their natal areas to reproduce. How animals accomplish such feats of natal homing has remained an enduring mystery. Salmon are known to use chemical cues to identify their home rivers at the end of spawning migrations.

The sensory ecology of ocean navigation.

How animals guide themselves across vast expanses of open ocean, sometimes to specific geographic areas, has remained an enduring mystery of behavioral biology. In this review we briefly contrast underwater oceanic navigation with terrestrial navigation and summarize the advantages and constraints of different approaches used to analyze animal navigation in the sea. In addition, we highlight studies and techniques that have begun to unravel the sensory cues that underlie navigation in sea turtles, salmon and other ocean migrants.

Magnetic maps in animals: nature's GPS.

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.

Animal behaviour: geomagnetic map used in sea-turtle navigation.

Migratory animals capable of navigating to a specific destination, and of compensating for an artificial displacement into unfamiliar territory, are thought to have a compass for maintaining their direction of travel and a map sense that enables them to know their location relative to their destination. Compasses are based on environmental cues such as the stars, the Sun, skylight polarization and magnetism, but little is known about the sensory mechanism responsible for the map sense. Here we show that the green sea-turtle (Chelonia mydas) has a map that is at least partly based on geomagnetic cues.