First published online May 19, 2008
Journal of Experimental Biology 211, 1719-1728 (2008)
Published by The Company of Biologists 2008
doi: 10.1242/jeb.015792
The sensory ecology of ocean navigation
Kenneth J. Lohmann*,
Catherine M. F. Lohmann and
Courtney S. Endres
Department of Biology, University of North Carolina, Chapel Hill, NC
27599, USA
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Fig. 1. Diagram illustrating potential problems in attempting to infer mechanisms
of navigation from the tracks of animals. (A) Overhead view of the track of a
hypothetical sea turtle moving hundreds of kilometers through the ocean and
monitored with satellite telemetry; events that occurred along the way are
indicated. (B) A plausible but erroneous interpretation of the turtle's path.
In this hypothetical example, researchers unaware of what happened in the
ocean superimposed the track on several topographical and geophysical maps
until correlations were found between changes in the turtle's behavior and
specific features of the environment. These environmental cues were then
assumed to have elicited the behavioral changes, leading to incorrect
inferences about navigational mechanisms.
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Fig. 2. (A) Diagrammatic representation of the Earth's magnetic field illustrating
how field lines (represented by arrows) intersect the Earth's surface, and how
inclination angle (the angle formed between the field lines and the Earth)
varies with latitude. At the magnetic equator (the curving line across the
Earth), field lines are parallel to the Earth's surface. The field lines
become progressively steeper as one travels north toward the magnetic pole,
where the field lines are directed straight down into the Earth and the
inclination angle is 90°. (B) Diagram illustrating four elements of
geomagnetic field vectors that might, in principle, provide turtles with
positional information. The field present at each location on Earth can be
described in terms of a total field intensity and an inclination angle. The
total intensity of the field can be resolved into two vector components: the
horizontal field intensity and the vertical field intensity. (Whether animals
are able to resolve the total field into vector components is not known.)
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Fig. 3. Orientation of hatchling loggerhead turtles in magnetic fields
characteristic of three widely separated locations (marked by black dots on
the map) along the migratory route. Generalized main currents of the North
Atlantic gyre are represented on the map by arrows. In the orientation
diagrams, each dot represents the mean angle of a single hatchling. 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. Figure
modified from Lohmann et al. (Lohmann et
al., 2001 ).
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Fig. 4. Evidence for a magnetic map in juvenile green turtles. Juvenile turtles
were captured in feeding grounds near the test site in Florida, USA. Each
turtle was exposed to a magnetic field that exists at one of two distant
locations (represented by stars along the coastline). Turtles exposed to the
field from the northern site swam approximately south, whereas those exposed
to the field from the southern site swam approximately north. 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. Figure
modified from Lohmann et al. (Lohmann et
al., 2004).
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Fig. 5. Ocean distribution of sockeye salmon (Oncorhynchus nerka) that
spawn in Iliamna Lake, Alaska. Salmon begin their spawning migrations from
widely separated locations that are sometimes more than 1000 km from the final
target area. Figure modified from Dittman and Quinn
(Dittman and Quinn, 1996).
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Fig. 7. Diagram of wave refraction patterns around an island in the open ocean. As
waves pass around an island, the parts that encounter shallow water are slowed
relative to the parts remaining over deeper water. As a result, refraction
occurs and a pattern of wave interference often forms on the leeward side of
the island.
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© The Company of Biologists Ltd 2008
