Navigation

1. Navigation Migration & Homing both involve timing (when to move) and navigation (direction)

2. How animals find their way • Some learn by moving with older ones. • But, a shining cuckoo can fly 4000km from NZ to Solomon Islands without ever meeting its own sp.  behaviour must be innate

3. Navigation An animal must have: a sense of direction (some form of compass) a sense of location (where it is starting from) "Well according to the Global Positioning System we are exactly in the middle of nowhere."

4. Animal compasses • To find out if an animal uses a particular cue it is eliminated by blocking off the sense used to detect it i.e. light – cover eyes/use mirrors

5. Sun compasses • Many migratory birds have a sun compass • Must allow for ‘the time of day’ & season • caged birds tend to orientate to direction of migration. Sun compass e.g. bee dances

6. Seasons Summer sun Winter sun

7. Changing the orientation of light When mirrors changed the direction of the light, birds orientated themselves relative to the reflected sun’s rays.

8. 10am 90° Direction of migration

9. 3pm 180° Direction of migration

10. 10am mirror 90° Direction of migration

11. Changing the time of day • When their internal clock was delayed, the birds orientated themselves relative to their perceived time – not to the actual time.

12. Actual time 3pm 90° Direction of migration ‘Bird time’ 10am

13. Disadvantage of a solar compass Sun is not always visible • Many birds and insects can see UV light which passes through clouds. • Bees, fish and whales can even detect polarised light

15. Star compasses • Birds caged in a planetarium showed a strong tendency to move in the direction of their normal migration. • When the planetarium sky was rotated 180° the birds direction also reversed.

17. Moon compass Sandhoppers move towards the sea using the moon’s position and an internal clock to compensate for moon’s apparent movement

18. Using earth’s magnetic field • Many animals can sense Earth’s magnetic field. • On an overcast day the homing ability of pigeons with magnets on their heads was impaired yet those with brass rods were unaffected A chain of magnetic particles is visible inside this bacterium. This simple compass keeps the microscopic organisms always swimming north. Also found in sea turtles, whales

19. Magnetism vs Sunlight Pigeons released magnet or brass bar on their back. Sunny days - pigeons accurately used the sun as a compass Cloudy days - magnets disorientated the birds. Each dot represents the birds vanishing direction.

20. A primary compass More than one compass = greater accuracy. Sun and star compasses used when possible • Learned • Very important When cloudy, use magnetic compasses • inborn Some animals use environmental cues such as chemical characteristics (salmon) and infra-sound of surf or wind

21. Experience and learning Important role Migrating birds caught and shifted. Experienced birds corrected error. Juvenile birds continue in displaced direction • Sense of direction innate • Map needed for navigation has to be learned. • Landmarks/visual signals e.g. digger wasps • Scent trails e.g. foraging ants, salmon