Presentation on theme: "Navigation Migration & Homing both involve timing (when to move) and navigation (direction)"— Presentation transcript:
Navigation Migration & Homing both involve timing (when to move) and navigation (direction)
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 2
Navigation An animal must have: a sense of direction (some form of compass) a sense of location (where it is starting from) 3 "Well according to the Global Positioning System we are exactly in the middle of nowhere."
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 4
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. 5 Sun compass e.g. bee dances
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. 15
Moon compass Sandhoppers move towards the sea using the moon’s position and an internal clock to compensate for moon’s apparent movement 17
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 18 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
Magnetism vs Sunlight Pigeons released magnet or brass bar on their back. Sunny days Sunny days - pigeons accurately used the sun as a compass Cloudy days Cloudy days - magnets disorientated the birds. 19 Each dot represents the birds vanishing direction.
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 20
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 21
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