Introduction to Navigation - PDF Free Download

Feb 21: Navigation--Intro Introduction to Navigation Definition: The process of finding the way to a goal Note: this is a broader definition than some scientists use Questions about navigation How do they do it? -- some "aren't animals amazing" stories Desert ants Cataglyphis sp. Habitat: deserts of Africa and Mediterranean Environment unsuited for chemical trails, so ants must find their way visually Ant s foraging range: 100 m Ant s body length: 1 cm

Feb 21: Navigation--Intro Introduction to Navigation Definition: The process of finding the way to a goal Note: this is a broader definition than some scientists use Questions about navigation How do they do it? -- some "aren't animals amazing" stories Pigeon Pigeons displaced from their nest will return from release sites up to 500 miles away, even if they have never been more than 50 miles from home Top racing pigeons can complete 500-mile trip in about 10 hours, which means they are flying at their full flight speed, hence in a straight line

Feb 21: Navigation--Intro Answering the How question Sources of information animals use to find their way? (importance of considering the Umwelt concept) How do animals obtain and process navigational information (consider sensory, learning, and modulatory mechanisms) Consider the possibility that animals have "backup systems (Example: sun and polarized light in honey bee orientation) Bees with view of sun orient dances to it (and will also treat bright light as artificial sun) Orientation is unchanged if sun goes behind cloud! Thus, some feature in blue sky provides navigational information to bee

Feb 21: Navigation--Intro Answering the How question Sources of information animals use to find their way? (importance of considering the Umwelt concept) How do animals obtain and process navigational information (consider sensory, learning, and modulatory mechanisms) Consider the possibility that animals have "backup systems (Example: sun and polarized light in honey bee orientation) Sky is bright because of scattering of sunlight in atmosphere Scattering causes light to be polarized

Feb 21: Navigation--Intro Answering the How question Sources of information animals use to find their way? (importance of considering the Umwelt concept) How do animals obtain and process navigational information (consider sensory, learning, and modulatory mechanisms) Consider the possibility that animals have "backup systems (Example: sun and polarized light in honey bee orientation) Different points in sky have different angle of polarization relative to horizon Analyzing angle of polarization in particular patch of sky gives navigational information equivalent to that of sun

Feb 21: Navigation--Organizing diversity Organizing the Diversity of Navigational Abilities (or, why so many solutions to problem of finding way?) The basic task of finding a goal requires animal to determine both position and direction Direction: discriminate different body orientations Position: determine which is the correct direction (toward goal) Two major factors determine how difficult this task is, hence how complex the navigational mechanisms need to be The geometry of the goal The scale of the animal's movements

Feb 21: Navigation--Geometry of the goal a How tasks of finding position and direction vary with geometry of goal z x y Night Day z-axis (find correct stratum in volume): Do I need to go up or down? Which way is up? b y z-axis orientation x y-axis (find correct line on plane): Do I need to go toward or away from shore? Which way is shore? c y Sea Shore (Goal) Land y-axis orientation x,y (find point on plane): Do I need to go W, SE, or ENE? How to steer in correct 2-D trajectory? d x G x,y-orientation x,y,z (find point in volume): In which direction and how high is goal? How to steer in correct 3-D trajectory? z x y G x,y,z-orientation

Feb 21: Navigation--Intro How nature of navigational task is influenced by scale of movements Example: Sea turtle that needs to find her natal beach to mate and reproduce 200 m Near a beach, the turtle s task is y-axis orientation 200 km Starting out far from island where beach is, task is x,y orientation

Feb 21: Navigation--x,y case study Case study: x,y-orientation The task: find point on a plane Sun Compensation as Basis of Celestial Compass Sources of directional information Insects: Sun compass, Landmarks Birds: Sun compass, Landmarks, Magnetic compass 16:00 α 16 H α 12 F Sources of positional information Path integration (within home range) Learned landmark "maps" (within home range) in insects Large-scale map of geophysical gradients (for navigation from outside home range) Noon

Feb 21: Navigation--x,y case study x,y-orientation cont d: Path Integration Determine your position relative to home by integrating directions and distances traveled over outward path Example of learning that cannot fit into associative learning framework Animal doesn t merely encode experience Instead, derives new knowledge by performing computations on sensory input Can ants solve Pythagorean theorem?

Feb 21: Navigation--x,y case study x,y-orientation cont d: Using map to find position Map provides positional information independent of path integration Useful if animal has been displaced passively (e.g., blown off course) Nature of map information available depends on scale of distances traveled 3 2 1 G 3 3 2 3 ZONE 1: Goal visible ZONE 2: Goal not visible, but familiar landmarks are visible (BEES, ANTS) ZONE 3: No familiar landmarks, because you are outside home range--use geophysical gradients extrapolated from experience within home range (PIGEONS)

Feb 21: Navigation--maps versus sun arc Navigation in Birds: Position Fixing Using Knowledge of Sun s Arc? Sun Arc Hypothesis Birds work out position and direction from knowledge of sun s arc Birds know pattern of movement of sun low in sky and east in AM high in sky and south at Noon low in sky and west in PM) Birds know that being shifted in longitude will cause the sun to be at wrong elevation in sky at a given time of day If my clock says noon and sun is low in sky and rising, then I must have been displaced WEST OF HOME Map-and-Compass hypothesis Birds determine POSITION based on some kind of map) Birds discriminate DIRECTIONS using an independent compass based on sun and/or magnetic field BIRDS HAVE BOTH SUN COMPASS AND MAGNETIC COMPASS Test of sun-arc hypothesis Clock-shift birds 6 hours (so lights come on at noon, go off at midnight) At local noon, birds clock tells them it is dawn Displace birds 20 miles, release at local noon (sun is south; true homing direction is north, away from sun) Sun arc hypothesis Home R Overcast Days Map + magnetic compass Sunny Days Map + sun compass hypothesis Sun (south at noon) Predictions Sun-arc hypothesis: sun is high in sky, so it must be local noon where I am; that puts me way to the east of my home. To fly west, go 90 deg to right of sun Map + Sun Compass hypothesis: my map tells me I am south; my clock says it is dawn, my sun compass tells me sun is in east; to go north head 90 deg left of sun Map/Magnetic Compass hypothesis: my map tells me I am south; my magnetic compass points the way north

Feb 21: Navigation--vertebrate bicoordinate maps What is Nature of Map? Bicoordinate map based on geophysical gradients (trends) learned in vicinity of home Trends learned near home are extrapolated to determine displacements far from home 2 3 3 R y-3 y-2 y-1 y-2.5 3 L 1 G 2 3 y y+1 y+2 Gradient y (e.g., in magnetic inclination) y+3 x+3 x+2 x+1 x x-1 x-2 x-3 x-4 y+3 x-1.5 Gradient x (e.g., in magnetic intensity)

Feb 21: Navigation--sensory basis of vertebrate maps Sensory Basis of Map? Pigeons: biases in homing direction near magnetic anomalies, even on sunny days Sea Turtles: Dramatic shift in response to compass cues depending on magnetic inclination, implying that magnetic inclination is part of map Olfactory maps?

Feb 21: Navigation--Sun as compass Using The Sun As a Compass H Using sun as true compass requires compensating for its apparent movements relative to fixed features of earth s surface Critical feature of sun is its AZIMUTH 16:00 α 16 α 12 F Noon

A W Feb 21: Navigation--The dance as window on sun compensation in bees Learning and Sun Compass Orientation 270 315 N 0 45 90 E Sun s rate of movement varies over the day Sun azimuth function changes with season and latitude Solution: Learn current local sun-azimuth function Dance as a window on the sun compensation mechanisms used by bees If you know direction of flight, then dance tells you where the dancer determined the sun to be 225 135 B 360 180 S Azimuth ( ) Azimuth 315 270 225 180 135 90 45 0 a c c 14400 18000 21600 25200 28800 32400 36000 39600 43200 46800 50400 54000 b 6 8 10 12 14 16 18 Local Solar Time 57600 61200 64800 68400 72000 Food (Up) 20 20 40 75 40 75

Feb 21: Navigation--Vert mag compasses Magnetic Compasses In Birds (and Turtles) Birds and sea turtles use "inclination compass, not a compass based on polarity of field In northern hemisphere, North is direction in which field lines make small angle with vertical South is direction in which field lines make larger angle with vertical Strictly speaking, this type of compass tells bird the directions of the magnetic pole, and the magnetic equator In the southern hemisphere, going poleward will take you South, and going equatorward will take you north Evidence for an inclination compass in birds (and turtles) experimentally reverse inclination angle, but not horizontal component birds reverse their orientation Note: some animals use polarity compass

Feb 21: Navigation--Programs Navigational Programs and Ontogeny of Navigation in Birds Apparently innate programs guiding long-distance migration Innate migratory direction (seasonally correct, depending on changes in day-length) Sensory basis: magnetic compass (innate); stellar AUGUST compass (requires learning) Programmed changes in flight path SEPTEMBER corresponding to normal migratory route OCTOBER

Feb 21: Navigation--Programs How Turtle Hatchlings Stay on the Y-axis A succession of cues, an interplay of innate and individually acquired information Visual cues: brighter toward ocean Wave orientation: detect orbital accelerations (has been tested experimentally Magnetic orientation: turtles learn magnetic direction while orienting to waves