導航機制 (Mechanisms of Orientation and Navigation ─ 動物行為學 (Ethology) 鄭先祐...

導航機制 (Mechanisms of Orientation and

Navigation

─ 動物行為學 (Ethology)

鄭先祐 (Ayo)

國立臺南大學環境與生態學院生態科學與技術學系教授

Ayo NUTN Web: http://myweb.nutn.edu.tw/~hycheng/

大學部生態學與保育生物學學程 ( 必選 ) 2010 年秋冬

Ayo 教材 (動物行為學 2010) 2

Part 2. 存活 ( 與環境的互動關係 )

生物時鐘 (Biological Clocks) 導航機制 (Mechanisms of Orientation and

Navigation) 空間分佈的生態學與演化學 (The Ecology and

Evolution of Spatial Distribution) 覓食行為 (Foraging Behavior) 抗掠食行為 (Antipredator Behavior)


09 導航機制 (Mechanisms of Orientation

and Navigation) Levels of Navigational ability Multiplicity of orientation cues

Visual cues Magnetic cues Chemical cues Electrical cues and electrolocation


Animals depend on oriented movements

Both within and between habitats Animals respond to a complex and changing

environment by positioning themselves correctly in it And by moving from one part of it to another

Animals depend on proper orientation to key aspects of the environment For migration, seeking a suitable habitat, looking for

food returning home, searching for a mate, or identifying offspring


Levels of navigational ability

Many animals travel between home and a goal But they do not all do this in the same manner

Animal strategies for finding their way fall into three levels1. Piloting ( 引導 )

2. Compass orientation ( 羅盤定位 )

3. True navigation ( 真領航 )


1. Piloting

The ability to find a goal by referring to familiar landmarks The animal may search randomly or systematically for

landmarks The guidepost may be any sensory modality

Magnetic cues guide sea turtles during their oceanic travels

Olfactory cues guide salmon during their upstream migration


2. Compass orientation

Animals head in a geographical direction without using landmarks Use the sun, stars, and

earth’s magnetic field as compasses

If they are displaced before beginning migration Animals can end up in

ecologically unsatisfactory places

Compass orientation is indicated if an animal is moved to a distant location and does not compensate for the relocation


Compass orientation

Displaced birds did not reach their normal destination and ended up in ecologically unsatisfactory places


Uses for compass orientation: vector navigation

Compass orientation can be used in Short-distance and long-distance navigation

Vector navigation: an inherited (innate) program that tells juveniles in which direction to fly and how long to fly Birds in the laboratory flutter in the direction in which

they would be flying if they were free Captive birds cease their activity at the same time as

free-living birds have completed their migratory journey


Animals can change compass bearing

Many species (i.e. that fly from central Europe to Africa) change compass bearing during their flight

Garden warblers and blackcaps in the laboratory change the direction in which they flutter in their cages At the same time free-flying members change direction

Migratory direction is inherited Offspring of crossbreeding two populations of blackcaps

that had different migratory directions oriented in a direction intermediate between their parents

Migratory direction is inherited by additive effects of genes


→The Garden Warbler, Sylvia borin, is a common and widespread typical warbler which breeds throughout northern and temperate Europe into western Asia. This small passerine bird is strongly migratory, and winters in central and southern Africa.

←The Blackcap, Sylvia atricapilla, is a common and widespread sylviid warbler which breeds throughout northern and temperate Europe. the Blackcap's closest living relative is the Garden Warbler which looks different but has very similar vocalizations.


Uses for compass orientation: path integration

Path integration (dead reckoning): the animal integrates information on the sequence of direction and distance traveled during each leg of the outward journey Then, knowing its location relative to home, the animal

can head directly there, using its compass(es)


Path integration

Information from the outward journey is used to calculate the homeward direction (vector) Path integration may be a type of vector navigation

Estimates of distance and direction are adjusted For displacement due to current or wind

Close to home, landmarks pinpoint the exact location of home

Desert ant


Many animals use path integration

While foraging, a desert ant wanders far from its nest After locating prey, the ant heads directly toward home

The ant knows its position relative to its nest Each turn and the distance traveled on its outward trip

To determine the direction and distance of its outward route Direction is determined using the pattern of polarization of

skylight, which is caused by the sun’s position Distance integrates the number of strides and stride length

(a “pedometer”) At home, cues in the nest reset the path integrator to zero

It is set again by the next outward journey


3. True navigation

The ability to maintain or establish reference to a goal, regardless of its location, without use of landmarks

The animal cannot directly sense its goal If displaced while en route, it changes direction to head

again toward its goal Only a few species (i.e. homing pigeons) have true

navigational ability Oceanic seabirds and swallows ( 燕子 ) Sea turtles and the spiny lobster


An animal that finds its way by using true navigation can compensate for experimental relocation and travel toward the goal.


Astounding feats( 令人驚奇的事蹟 ) of migration

Different species use different navigational mechanisms An arctic tern circumnavigates the globe A monarch butterfly flutters thousands of miles to

Mexico A salmon returns to the stream in which it hatched

Orientation systems include: multiple cues, a hierarchy of systems, transfer of information among various systems

A species can use several navigational mechanisms If one mechanism becomes inoperative, a backup is used Navigational systems may use multiple sensory systems


Visual cues: landmarks

An easily recognizable cue along a route that can be quickly stored in memory to guide a later journey Based on any sensory modality, but is most commonly visual

The digger wasp relies on landmarks to relocate its nest after a foraging flight A ring of 20 pine cones was placed around the nest’s opening When a female wasp left the nest, she flew around the area,

noting local landmarks, and then flew off in search of prey When the ring of pinecones was moved, the returning wasp

searched the middle of the pine cone ring for the nest opening


Orienting with landmarks

Homing pigeons wearing frosted contact lenses did not see well Their flight paths were still oriented toward home

Pigeons do not need landmarks to guide their journey home But they may use landmarks when they are available


Models of landmark use

Species use landmarks in different ways One model of landmark use: the animal stores the image

of a group of landmarks in its memory, almost like a photograph Then it moves around until its view of nearby objects

matches the remembered “snapshot A series of memory snapshots might be filed in the order

in which they are encountered Desert ants use path integration to return to the nest

They also use landmarks, especially when they have almost reached the nest


Desert ants use memory snapshots of landmarks

Close to the nest entrance, they search systematically to find the nest’s opening The search strategy varies with the species and number of

landmarks If available, ants use landmarks

If the direct path is unfamiliar At a clearing, it uses path integration


Visual cues: sun compass

Many animals use the sun as a celestial compass Determining compass direction from the position of the

sun The specific course that the sun takes varies with the

latitude of the observer and the season of the year But it is predictable


The sun follows of predictable path through the sky that varies with latitude and season.


The sun can be used as a compass

If the sun’s path and the time of day are known The sun appears to move at about 15° an hour

Species that take short trips do not adjust their course An animal traveling for long periods compensates for the

sun’s movement It measures the passage of time and adjusts its angle with

the position of the sun After 6 hours of travel, an animal switches from having the

sun 45° to its left to a 45° angle, with the sun on its right Time is measured by using a biological clock


Daytime migrants navigate by the sun

Orientation (directionality) of migratory restlessness is lost when the sun is blocked from view

Caged starlings are daytime migrants They lose their directional ability

under an overcast sky When the sun reappears, they orient

correctly again Birds orient to a new direction of the

“sun” when a mirror is used to change the apparent position of the sun

Starling ( 歐掠鳥 )


Experiments using migratory restlessness

An orientation cage has 12 food boxes encircling a birdcage Birds were trained to expect food

in a box in a certain compass direction

As long as the birds could see the sun, they approached the proper food box

They compensate for the sun’s movement


Compensation for the sun’s movement

Is through the biological clock Which can be reset by artificially altering the light-dark

regime Exposing a bird to a light-dark cycle that is shifted so that

the lights come on at noon instead of 6 am Sets animal’s body time six hours later than real time Orientation is shifted 90° (6 x 15°) clockwise, west instead

of south


A clock-shift experiment demonstrates time-compensated sun compass orientation.


Visual cues: star compass

Many species of bird migrants travel at night Steering their course using stars

Caged warblers housed in a planetarium oriented themselves in the proper migratory direction for that time of year When the star pattern of the sky was rotated, the birds

oriented according to the sky’s new direction When the dome was diffusely lit ( 光線擴散 ), the birds

were disoriented


Star compass orientation in indigo buntings In planetarium( 天象儀 ) studies, these birds rely on

the region of the sky within 35° of Polaris ( 北極星 )


Indigo Bunting

It is migratory, ranging from southern Canada to northern Florida during the breeding season, and from southern Florida to northern South America during the winter.

It often migrates by night, using the stars to navigate.

The Indigo Bunting, Passerina cyanea, is a small seed-eating bird in the family Cardinalidae.


Stars rotate around Polaris ( 北極星 )

Polaris provides the most stationary reference point in the northern sky Other constellations rotate around it

Birds learn that the center of rotation of the stars is in the north Which guides their migration northward or southward

It is not necessary for all constellations to be visible at once


The stars rotate around Polaris, the North Star. The positions of stars in the northern sky during the spring are shown here.


The axis of rotation gives directional meaning

Once their star compass has been set, birds do not need to see the constellations rotate Simply viewing certain constellations is enough

The star compass has been studied in only a few species Garden warblers and pied flycatchers also learn that

the center of celestial rotation indicates north


Young birds were oriented to Betelgeuse( 參宿四，位於獵戶座 )

Birds that had experienced Betelgeuse, not Polaris, as the center of rotation interpreted the position of that star as north And headed away from it for their southern migration


The orientation of indigo buntings to a stationary planetarium sky after exposure to different celestial rotations.


Visual cues: polarized light

Many animals orient correctly even when their view of the sky is blocked

Another celestial orientation cue is available in patches of blue sky

Light consists of many electromagnetic waves vibrating perpendicularly to the direction of propagation


The nature of polarized light

Unpolarized light: light waves vibrate in all possible planes perpendicular to the direction in which the wave is traveling

In polarized light: all waves vibrate in only one plane Sunlight passing through the atmosphere becomes

polarized by air molecules and particles The degree and direction depend on the position of the

sun


The sky viewed through a polarizing filter to show the pattern of skylight polarization at (a) 9am (b) noon, and (c) 3pm. The diagrams below show the pattern of polarization.


The pattern of polarized light

Is related to the sun’s position One aspect of this pattern is the degree of polarization

The light at the poles is unpolarized Becoming more strongly polarized away from the poles

The e-vector: the direction of the plane of polarization also varies according to the position of the sun It is always perpendicular to the direction in which the

light beam is traveling The pattern moves westward as the sun moves


Uses of polarized light in orientation

Polarized light reflected from shiny surfaces (i.e. water or a moist substrate) Attracts some aquatic insects to suitable habitat

Horizontally polarized light reflected from the surface of a pond helps the backswimmer locate a new body of water


Backswimmers

Backswimmers get their common name from their characteristic habit of swimming on their backs. Although they must surface for air, they often swim around below the surface of the water.

Backswimmers or Back-swimmers (Family Notonectidae) are common in ponds and other still waters here in southeastern Arizona and throughout most of the rest of North America.


The plane of polarization is an orientation cue

Polarized light is used as an axis for orientation Salamanders living near a shoreline use the plane of

polarization to direct their movements toward land or water

It can determine the sun’s position when blocked from view And provide orientation cues at dawn and dusk, when the

sun is below the horizon


Magnetic cues

Magnetic sense helps an organism locate a preferred direction i.e. when bacteria swim toward the muddy bottom

The earth’s magnetic field may also orient nest building In the Ansell’s mole rat, or roosting place of bats

A magnetic compass evolved in non-migratory birds first Optimized paths to and from nest, feeding, and drinking sites

Advantages to using the earth’s magnetic field as a compass: Used where visual cues are limited or absent Unlike celestial cues, it is constant year round, night and day


Cues from the earth’s magnetic field

The magnetic poles are shifted slightly from the geographic, or rotational, poles

The earth’s magnetic declination: the difference between the magnetic pole and the geographic pole Small in most places (< than 20°) Magnetic north is usually a good indicator of

geographic north Polarity, inclination, and intensity of the earth’s

magnetic field vary with latitude to provide three potential orientation cues


The earth’s magnetic field.


The magnetic field provides orientation cues

Spiny lobster and certain fish and birds, rats and bats respond to polarity

Most birds and sea turtles use the angle of inclination They distinguish between “poleward” (steep lines of

force) and “equatorward” (lines of force parallel to the earth)

The horizontal component of the earth’s field (the polarity) indicates the north-south axis

The vertical component (the inclination of the field) tells whether it is going toward the pole or equator


Ansell’s mole rats orient using polarity

They build nests in the southeastern part of their enclosure

When the horizontal component (the polarity) was reversed The rats built nests in the northwest sector of the arena

When the vertical component (the angle of inclination) was inverted They continued nesting in the southeast sector


The earth’s magnetic field can serve as a compass (a) mole rats respond to the polarity (horizontal component) of the ambient magnetic field.


Birds orient using the inclination angle

In the laboratory, European robins oriented in the proper direction even without visual cues


Birds use the inclination of the lines of force (vertical component of the earth’s magnetic field) as a compass. The lines of force are steepest at the poles and horizontal at the equator.

Birds orient using the inclination angle


Homing pigeons use the angle of inclination

On cloudy days, pigeons rely on magnetic cues instead of their sun compass Orienting as if north is the direction where the magnetic

lines of force dip into the earth

Birds that were misdirected by reversed magnetic information Headed away from home


The Earth’s magnetic field serve as a magnetic compass

Animals respond to the intensity of the geomagnetic field Bees Homing pigeons Sea turtles American alligator

If changes in magnetic intensity can be sensed The gradual increase in strength between

the equator and the poles could also serve as a crude compass


An inherited migratory program

Migratory birds inherit a program telling them to travel in a geographical direction based on magnetic cues for a certain amount of time They fly toward the equator (horizontal lines of force) in the

fall and toward the pole (vertical lines of force) in the spring

Some birds cross the equator during migration and keep going They reverse their migratory direction with respect to the

inclination compass They now fly “poleward” instead of “equatorward” Experience: the switch that causes the birds to fly

“poleward”


The sensitivity of the magnetic compass

Corresponds to the strength of the earth’s magnetic field

A bird does not respond to magnetic fields that are stronger or weaker than typical in the area where it has been living

Sensitivity may be adjusted by exposure to a field of a new strength for a period of time Responsiveness is fine-tuned during migration


The magnetic compass of sea turtles

Sea turtles travel tens of thousands of kilometers during their lifetimes Continuously swimming for

weeks With no land in sight

Loggerhead sea turtles are guided by the earth’s magnetic field


A hatchling sea turtle’s magnetic compass

Is based on the inclination of the magnetic lines of force Similar to a bird’s compass

Hatchlings swim toward magnetic northeast in the normal geomagnetic field And continue to do so when the field is experimentally

reversed


A sea turtle’s journey begins after hatching

Using local cues to head toward the ocean When they first enter the ocean, they swim into the

waves To maintain an offshore heading, taking them out to sea

In the open ocean, waves are not a navigational cue They can come from any direction

Sea turtles maintain the same angle with the magnetic field that they assumed while swimming into the waves to stay on course


Is there a magnetic map ( 磁場地圖 )?

True navigation requires not only a compass but also a map The map is used to know one’s position relative to the

goal A compass guides the journey in a homeward direction

An animal has a magnetic map if it can obtain positional information from the Earth’s magnetic field Relative to a target or goal

The map may be inherited or learned Specific or general


Magnetic signposts ( 磁場路標 )

Magnetic maps consist of inherited responses to landmarks Signposts ( 路標 ) trigger changes in direction

Signposts occur along the migratory pathways of the pied flycatcher Key geographical locations have characteristic magnetic

fields These fields act as signposts telling them to shift flight

direction Birds avoid the Alps, Mediterranean Sea, and central

Sahara


Magnetic signposts affect sea turtles

Triggering changes in swimming direction during the open-sea navigation of sea turtles

Hatchling loggerhead sea turtles first swim toward magnetic northeast using the earth’s magnetic field as a compass Bringing them to the Gulf Stream Then to the North Atlantic gyre ( 北大西洋流 ), a

circular current that flows clockwise around the Sargasso Sea ( 藻海 )

Where they remain for 5 to 10 years


Young sea turtles are programmed to swim

Hatchling loggerheads that had never been in the ocean swam in a direction that would keep them in the gyre if they had been migrating

Regional differences in the earth’s magnetic field serve as navigational beacons ( 導航的燈塔 ) Guiding the open-sea migration of young loggerheads They have no conception of their geographic position or

goal


Magnetic signposts in the earth’s magnetic field may direct juvenile sea turtles in the proper direction to remain within the North Atlantic gyre.


The magnetic field is a map

Animals use the earth’s magnetic field as a map to locate their position relative to a goal Using inclination and the intensity of the earth’s magnetic

field The geomagnetic field may be more than a compass

Birds released at magnetic anomalies prefer magnetic valleys They detect and respond to spatial variability of the

geomagnetic field


The flight paths of pigeons in magnetic anomalies. The paths of these pigeons seem to follow the magnetic valleys, where the field strength is closer to the value at the home loft.


Sea turtle migration

As a sea turtle matures, it learns the geomagnetic topography of specific areas This is part of the map it uses to locate an isolated target

(i.e. a nesting beach) After spending years in the North Atlantic gyre

Sea turtles migrate between summer feeding grounds and winter feeding grounds in the south

Adults return to nest on the same beaches where they hatched


Sea turtles migrate with extraordinary precision

The earth’s magnetic field provides a global positioning system that tells them their position relative to a goal

Juveniles and adults use the geomagnetic field as navigational map A more complex use than hatchlings

The magnetic field tells the turtle whether it is north or south of its goal It moves in the appropriate direction until it encounters

other cues that identify the feeding grounds


As sea turtles mature, they use the earth’s magnetic field to determine their location relative to home. Sea turtles return to the same feeding grounds every year.

The turtle swam in a direction that would return them to their feeding grounds (the test site) if they actually had been displaced.


Light-dependent magnetoreception

Animals sense the earth’s magnetic field through at least two types of magnetoreceptors: light-dependent and magnetite

Light-dependent magnetoreception: involves specialized photoreceptors Is light dependent

Certain animals may “see” the earth’s magnetic field Photoreceptor molecules absorb light better under

certain magnetic conditions The amount of light absorption provides information

about the local magnetic field


Seeing the earth’s magnetic field. The visual field of a bird flying.


Light dependent magnetoreception in birds

The magnetoreceptor is located in the right eye Birds cannot remain oriented to a magnetic field in darkness

Light must of specific wavelengths Blue light is needed to remain oriented to a magnetic field Birds may orient to red light if they are given time to adjust

Cryptochrome: a photopigment involved in magnetoreception Stimulates photoreceptors differently depending on the

orientation of the magnetic field Migratory birds sense the magnetic field as a visual pattern


Cryptochromes

Cryptochromes are a class of blue light photoreceptors of plants and animals. They form a family of flavoproteins that regulate germination, elongation, photoperiodism, and other responses in higher plants. Cryptochromes are involved in the circadian rhythm of plants and animals, and in the sensing of magnetic fields in a number of species.

Cryptochrome 是一種藍光 / 紫外光受體，與果蠅生物鐘的控制有關。

Cryptochrome 可用作磁場的一種傳感器。


Cryptochrome

Cryptochrome absorbs blue-green light Wavelengths important for magnetic orientation In night-migratory birds, cryptochromes are produced at

night Nonmigratory birds produce cryptochromes during the day

Cryptochrome-containing cells of the retina connect to neurons in a brain region called Cluster N Neurons are active when night-flying migrants orient to a

magnetic field The retina and cluster N are connected through the

thalamus, a brain region important for vision


Magnetite ( 磁鐵礦 )

Magnetite: a magnetic mineral in animals It orients to the geomagnetic field Found in bees, trout, salmon, birds, and sea turtles In vertebrates, these deposits are found in the head or skull

It can twist to align with the earth’s magnetic field, stimulating a stretch receptor

In the rainbow trout, nerves contain fibers that respond to magnetic fields

Along with their light-dependent inclination compass, birds have magnetite deposits in their upper beak

The polarity compass of bats is based on magnetite


Two magnetoreceptor systems

Animals might have one or both types of magnetic sensitivity Light-dependent and magnetite Each serving a different purpose

Eastern red-spotted newts Use a light-dependent magnetic compass based on the

inclination of the magnetic lines of force when orienting toward the shore

Their homing ability is sensitive to polarity changes


Magnetoreception in migratory birds

The two mechanisms of magnetoreception serve different functions The light-dependent mechanism: a magnetic compass The magnetite based mechanism: detects minute

variations in earth’s magnetic field and is part of the magnetic “map” receptor

To use the geomagnetic field as a map, an animal compares the local intensity of the field with that at the goal


Juvenile vs. adult silvereye receptor systems

Adult, not juvenile, migrants have a navigational map Juvenile silvereyes remained oriented in the appropriate

migratory direction after a magnetic pulse They have not yet formed a magnetic map Their orientation is based on an innate migratory program They use their magnetic compass, based on the light-

dependent magnetoreception process, to head in the appropriate direction


Chemical cues

Some species use olfactory cues for orientation during homing

Olfaction and salmon homing Salmon hatch in the cold, clear fresh water of rivers or

lakes and then swim to sea After several years, they reach their breeding condition

and return to the very river from which they came Swimming upstream, they return to the specific location

of the natal stream in which they were born


Salmon return to their incubation site

Researchers buried salmon embryos at the bottom of a pond The embryos emerged and migrated to the sea And then migrated back to the creek

The marked salmon returned to the site of their incubation The pond


A map of Hansen creek, Alaska, showing the distribution of olfactory cues in different regions of the creek area.


Salmon migration depends on olfactory cues

Navigation in the open seas depends on several sensory cues Magnetism, sun compass, polarized light, and odors

The olfactory hypothesis of salmon homing: young salmon learn the odors of the home stream The odor is a mixture of amino acids in the water

Salmon use olfactory cues to locate the mouth of the river in which they hatched Following a chemical trail to the tributary where they hatched If they choose the wrong branch, they return to the fork and

swim up another branch


Mosaic model of avian olfactory navigation

Pigeons form a mosaic map of environmental odors within a radius of 70–100 kilometers of their home loft Some of this map takes shape as young birds experience

odors at specific locations during flight More distant features of the map are filled in as wind

carries faraway odors to the loft The bird associates each odor with the direction of the

wind carrying it


Gradient model of olfactory navigation

Assumes that there are stable gradients in the intensity of one or more environmental odors

Wherever it was, the bird determines the strength of the odor and compares it to the remembered intensity at the home loft

The gradient model demands that the bird make both qualitative and quantitative discriminations The mosaic model requires only that the bird make

qualitative discriminations among odors


Distorting the olfactory map

Manipulating olfactory information distorts the bird’s olfactory map Deflecting wind by wooden baffles makes it seem that

odors come from another direction A pigeon forms a shifted olfactory map But, the shift in orientation might be due to something other

than a distorted olfactory map The baffles also deflect sunlight, and change the sun

compass


The results of an experiment that manipulated a pigeon’s olfactory information.

(a) the experimental pigeons were kept in a loft that was exposed to natural odors, as well as to a breeze carrying the odor of benzaldehyde from a source northwest of the loft.


Depriving birds of their sense of smell

Olfaction plays an important role in pigeon homing Anosmic pigeons (birds deprived of their sense of

smell) are less accurate in their initial orientation And fewer return home from an unfamiliar, but not

from a familiar, release site The procedures do not affect the birds’ motivation to

return home Anosmic pigeons home as well as control pigeons

when they are released from familiar sites


Electrical cues and electrolocation

Electrical cues have many uses for those organisms that can sense them Predators use electrical cues from organisms to detect prey Electrical fields generated by nonliving sources (i.e. ocean

currents, waves, tides and rivers) provide cues for navigation

There is no evidence that migrating fish such as salmon, shad, herring, or tuna are electroreceptive But electrical features of the ocean floor may help guide the

movements of bottom-feeding species (i.e. dogfish shark)


Some aquatic species have electric organs

That generate pulses, creating electrical fields used in communication and orientation

The electric organs located near the tail of weak electric fish generate brief electrical pulses Creating an electrical field around the fish - the head acts

as the positive pole and the tail as the negative pole Nearby objects distort the field These distortions are detected by electroreceptors in the

lateral lines on the sides of the fish


小口彎頜象鼻魚 (Campylomormyrus phantasticus)


Electrolocation is useful

In muddy water or in fish that are active at night

In distinguishing between living and nonliving objects in the environment An object with greater conductivity

than that of water (i.e. another animal) directs current toward itself

Objects that are less conductive (i.e. a rock) deflect the current away


Fish use electrical fields to explain their environment

Distortions in the electrical field create an electrical image of objects Telling a fish a great deal about its environment Varies according to the location of the object The location of the image on its skin tells the fish where

the object is located The fish performs a series of movements close to the

object under investigation To provide sensory input that helps the fish determine

the object’s size or shape


Summary

Navigational strategies are grouped into three levels Piloting, compass orientation, true navigation

Vector navigation: an inherited program that tells a bird to fly in a given direction for a certain length of time

Path integration: memorizing direction and distance on the outward journey and use of a compass to travel directly home

True navigation requires a map and a compass Visual cues are: landmarks, the sun, stars, moon and

polarization Animals must learn to use the sun as a compass


Summary

Birds learn that the center of celestial rotation is north The earth’s magnetic field provides cues for

orientation: polarity, inclination, and intensity Animals develop a detailed magnetic map with

experience Two types of magnetoreceptors: light dependent and

deposits of magnetite Some species use olfactory cues for orientation during

homing Some aquatic species can use electrical fields or

organs for navigation and communication


問題與討論

[email protected]

Ayo 台南 NUTN 站 http://myweb.nutn.edu.tw/~hycheng/

導航機制 (Mechanisms of Orientation and Navigation ─ 動物行為學 (Ethology) 鄭先祐...

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