introduction to navigation - michigan state university › course › zol › 313 › spring ›...

Definition: The process of finding the way to a goal

Questions about navigation

Feb 21: Navigation--Intro

Introduction to Navigation

• Note: this is a broader definition than some scientists use

• How do they do it? -- some "aren't animals amazing" stories

Desert antsCataglyphis sp.

• Habitat: deserts of Africa andMediterranean

• Environment unsuited for chemical trails,so ants must find their way visually

• Ant’s foraging range: 100 m• Ant’s body length: 1 cm







Monarch butterfly

Fall migration

Spring migration

Overwintering roost in Mexico







Pigeon

• Pigeons displaced from their nest will return fromrelease sites up to 500 miles away, even if theyhave never been more than 50 miles from home

• Top racing pigeons can complete 500-mile trip inabout 10 hours, which means they are flying at theirfull flight speed, hence in a straight line







Green Sea Turtle

Adults return to their birth place on Ascension Islandafter several years of feeding off coast of Brazil

• 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)


Answering the “How” question

• Bees with view of sun orient dances to it (and willalso 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






• Sky is bright because of scattering ofsunlight in atmosphere

• Scattering causes light to be polarized






• Different points in sky have different angle ofpolarization relative to horizon

• Analyzing angle of polarization in particularpatch of sky gives navigational informationequivalent to that of sun

• The basic task of finding a goal requires animalto determine both position and direction

• Direction: discriminate different bodyorientations

• Position: determine which is the correctdirection (toward goal)

Feb 21: Navigation--Organizing diversity

Organizing the Diversity of Navigational Abilities(or, why so many solutions to problem of finding way?)

• Two major factors determine how difficult thistask is, hence how complex the navigationalmechanisms need to be

• The geometry of the goal• The scale of the animal's movements

Feb 21: Navigation--Geometry of the goal

z

x

y

x

y

x

y

z

x

y

G

G

Sea LandShore(Goal)

a

b

c

d

Night

DayHow tasks of finding position and

direction vary with geometry of goal

z-axis orientationz-axis (find correct stratum in volume): Do I need to go up or down?Which way is up?

y-axis orientation

y-axis (find correct line on plane): Do I need to go toward or away from shore?Which way is shore?

x,y-orientationx,y (find point on plane):

Do I need to go W, SE, or ENE?How to steer in correct 2-D trajectory?

x,y,z-orientation

x,y,z (find point in volume): In which direction and how high is goal?How to steer in correct 3-D trajectory?


How nature of navigational task isinfluenced by scale of movements

Example: Sea turtle that needs to findher natal beach to mate and reproduce

200 m

Near a beach, the turtle’s task isy-axis orientation

200 km

Starting out far from island wherebeach is, task is x,y orientation

The task: find point on a plane

Sources of directional information• Insects: Sun compass, Landmarks• Birds: Sun compass, Landmarks, Magnetic

compass

Feb 21: Navigation--x,y case study

Case study: x,y-orientation

H

F

Noon

16:00α12

α16

Sun Compensation as Basis of Celestial Compass

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)

Determine your position relative tohome by integrating directions anddistances traveled over outward path


x,y-orientation cont’d: Path Integration

• Example of learning that cannot fit intoassociative learning framework

• Animal doesn’t merely encode experience• Instead, derives new knowledge by performing

computations on sensory input

Can ants solve Pythagorean theorem?

• 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


x,y-orientation cont’d: Using map to find position

G1

23

3

3

3

2

ZONE 1: Goal visibleZONE 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 UsingKnowledge of Sun’s Arc?

Sun Arc Hypothesis Birds work out position anddirection 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)

Map-and-Compass hypothesis• Birds determine POSITION based on some

kind of map)• Birds discriminate DIRECTIONS using an

independent compass based on sun and/ormagnetic field

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)

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 ofmy home. To fly west, go 90 deg to right of sun

• Map + Sun Compass hypothesis: my map tells me I amsouth; my clock says it is dawn, my sun compass tellsme sun is in east; to go north head 90 deg left of sun

• Map/Magnetic Compass hypothesis: my map tells me Iam south; my magnetic compass points the way north

Sun arc hypothesis Map + sun compass hypothesis

Map + magnetic compass

Sunny Days

Overcast Days

Sun (south at noon)

Home

R

BIRDS HAVE BOTH SUN COMPASSAND MAGNETIC COMPASS

• Birds know that being shifted in longitudewill cause the sun to be at “wrong” elevationin sky at a given time of day

• If my clock says noon and sun is low insky and rising, then I must have beendisplaced WEST OF HOME

Feb 21: Navigation--vertebrate bicoordinate maps

What is Nature of Map?

G1

23

3

3

3

2

L

R

xx+1x+2x+3 x-1 x-2 x-3 x-4

y+3

y+2

y+1

y

y-1

y-2

y-3

y+3

y-2.5

x-1.5

• Bicoordinate map based on geophysical gradients (trends) learned in vicinity of home• Trends learned near home are extrapolated to determine displacements far from home

Gradient y (e.g., inmagnetic inclination)

Gradient x (e.g., inmagnetic 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 magneticinclination, implying that magnetic inclination is part of map

• Olfactory maps?

Feb 21: Navigation--Sun as compass

Using The Sun As a Compass

H

F

Noon

16:00α12

α16• Using sun as true compass requirescompensating for its apparent movementsrelative to fixed features of earth’s surface

• Critical feature of sun is its AZIMUTH

Feb 21: Navigation--The dance as window on sun compensation in bees

Learning and Sun Compass Orientation

0

45

90

135

180

225

270

315

360

1440

018

000

2160

025

200

2880

032

400

3600

039

600

4320

046

800

5040

054

000

5760

061

200

6480

068

400

7200

0

Azi

mut

h

A

B

a

b

c

c

6 8 10 12 14 16 18 Local Solar Time

E

S

W

N0°

45°

90°

135°

180°

225°

270°

315°

J

J

J

JJ

JJJJJJ

J

J

J

J

Azi

mut

h (°

)

Sun’s rate of movement varies over the daySun azimuth function changes with season and latitudeSolution: Learn current local sun-azimuth function

Food

(Up)

20° 40° 75°

20°40°

75°

Dance as a window on the sun compensationmechanisms used by bees

If you know direction of flight, then dance tellsyou where the dancer determined the sun to be

Feb 21: Navigation--Vert mag compasses

Strictly speaking, this type of compass tells bird thedirections of the magnetic pole, and the magnetic equator

• In the southern hemisphere, going “poleward” will takeyou South, and going “equatorward” will take you north

Evidence for an inclination compass in birds (andturtles)

• experimentally reverse inclination angle, but nothorizontal component

• birds reverse their orientation• Note: some animals use polarity compass

Birds and sea turtles use "inclination compass,” not acompass based on polarity of field

• In northern hemisphere, North is direction in which fieldlines make small angle with vertical

• South is direction in which field lines make larger anglewith vertical

Magnetic Compasses In Birds (and Turtles)

Feb 21: Navigation--Programs

Navigational “Programs” and Ontogeny of Navigation in Birds

• Programmed changes in flight pathcorresponding to normal migratory route

• Innate migratory direction (seasonally correct,depending on changes in day-length)

• Sensory basis: magnetic compass (innate); stellarcompass (requires learning)

Apparently innate programs guiding long-distance migration

AUGUST

SEPTEMBER

OCTOBER

Feb 21: Navigation--Programs

How Turtle Hatchlings Stay on the Y-axisA succession of cues, an interplay of innateand 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

introduction to navigation - michigan state university › course › zol › 313 › spring ›...

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