PowerPoint Presentation - Migration and Navigation by ewghwehws

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									Migration and Navigation
 • Migration examples
 • Navigational strategies
   – Piloting
   – Path integration
   – Compass orientation
 • Navigational mechanisms
   – Compass cues
       Why migrate?

• Increase availability of food
• Avoid cold weather
• Decrease risk of predation on
  juveniles
 Monarch butterflies
                    300 million




Michoacan, Mexico
                      Spiny lobster




Move from shallow to deep water in the fall in long single file lines.
Females spawn in deep water in spring before returning.
Salmon
                    Green turtles




Nest on Ascension Is., feed off Brazil and return to same beach
 White-
 bearded
Wildebeest

1.5 million
animals
per year

Low levels of
phosphorus in
short grass
may stimulate
movement
Gray whales
    Lesser long-nosed bats




Feed on cactus going north, agave going south
                                     Radar tracking of fall migrants
N. American birds




254 species migrate to the tropics
Arctic terns




           Fly 40,000 km each year
         Navigational strategies
• Piloting
   – Use landmark to locate goal (nest, etc.)
• Path integration (dead reckoning)
   – compute net vector by integrating distance traveled
     with compass direction
   – Accumulates errors, only good for short distances
• Compass orientation
   – follow compass heading to goal or landmark
• True navigation
   – Use compass and map (cognitive) to plot route
                  Landmark orientation
• One landmark provides
  distance, but not direction
• Animal must remember
  location of goal relative to
  two or more landmarks
   – Evidence from bees and pigeons
     suggests that the animal has a
     mental template of landmark
     positions
   – Animals approach landmarks
     from a single compass direction.
     Consequently, the animal
     doesn’t have to memorize the
     template from all directions.
     Navigation by dead reckoning

                                                 Home




• Use the direction and distance of each successive leg
  during the outbound trip
• Compute net vector and use compass to return home
Cataglyphis ant homing

               When ants are picked
               up and moved, they
               travel in a parallel
               direction

               Ants use path integration




                          Wehner
3-D path integration by ants
                  Ant odometers record
                  horizontal distance moved
                  not actual distance traveled

                  Thus, they do not use time
                  or energy expended to
                  determine distance


              Trained uphill/downhill
              with food source 8.7 m

              Trained on flat track
              with food source 5.2 m

                     Wohlgemuth, S. 2001 Nature 411:795.
Starlings use a compass
Migratory direction is
heritable in blackcap
      warblers




      Brown: Germany
      White: Hungary
      Blue: F1
          Compass cues
• Sun
   – Time-compensated solar compass
   – Clock-shift experiments
   – Polarized light
• Stars
   – Nocturnal paths
   – Planetarium experiments
• Geomagnetic field
   – Pigeon homing experiments
   – Lateralization in robins
   – Turtle swimming
A solar compass requires time compensation
Logic of clock-shift experiments
     Pigeon homing after a 6 h clock-shift




Each dot represents the bearing chosen by a bird. Black dots are
control birds, color dots are experimentals. Dashed line is homeward.
When the sun is out, clock-shifted birds go SE rather than SW. On a
cloudy day, clock-shifted birds do not change direction indicating that
they are not using solar cues.
Polarized light indicates solar position
       on a partially cloudy day
Nocturnal flight paths implicate
      celestial compass




                           Veery
       Indigo buntings in planetariums




                                                   Control sky is no stars




Planetarium expts show that birds rely on rotational point to indicate north
Pigeon homing with Helmholz coils
          Magnetic compass is right eye/left
             brain dominant in robins




WILTSCHKO, W et al. 2002 Nature 419, 467 - 470

Orientation behaviour under monochromatic green light with the magnetic field as the only cue. The
mean headings of the 12 birds are indicated as triangles at the periphery of the circle; the grand mean
vector is represented by an arrow proportional to the radius of the circle (for numerical values, see
Table 1). The inner circles are the 5% (dotted) and the 1% (solid) significance border of the Rayleigh
test25. a, Binocular control (Bi) tested in the geomagnetic field. b, Monocular left eye (L) tested in the
geomagnetic field. c, d, Monocular right eye tested in the geomagnetic field (c; R) and in a magnetic
field with the vertical component inverted, so that the inclination was pointing upwards (d; R(UI)).
Turtles detect magnetism
Magnetic field cues

            Polarity:
            •lobsters, newts, salmon,
            mole-rats

            Inclination:
            •birds, sea turtles
            •in northern hemisphere N is
            indicated by the direction in
            which the force lines dip
            toward the earth

            Intensity: bees, alligators

								
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