09 cues Visual cues Magnetic cues Chemical cues

09 導航機制 導航能力的層級 導航與辨識方向的cues Visual(視覺) cues Magnetic(磁場) cues Chemical(化學) cues Electrical(電場) cues and electro-location 2 Ayo 教材 (動物行為學 2011 通識)

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 3 Ayo 教材 (動物行為學 2011 通識)

導航能力的層級 � Animal strategies for finding their way fall into three levels 1. Piloting (引導) 2. Compass orientation (羅盤定位) 3. True navigation (真領航) 4 Ayo 教材 (動物行為學 2011 通識)

1. Piloting(引導) �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 5 Ayo 教材 (動物行為學 2011 通識)

2. Compass orientation (羅盤定位) �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 Compass orientation is indicated �Animals can end up in if an animal is moved to a distant ecologically unsatisfactorylocation and does not compensate for the relocation places 6 Ayo 教材 (動物行為學 2011 通識)

Compass orientation Displaced birds did not reach their normal destination and ended up in ecologically unsatisfactory places 7 Ayo 教材 (動物行為學 2011 通識)

Uses for compass orientation: vector navigation �Compass orientation can be used in �Short-distance and long-distance navigation �Vector navigation: an inherited (innate) 8 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 Ayo 教材 (動物行為學 2011 通識)

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 9 blackcaps that had different migratory directions oriented in a direction intermediate between their parents Ayo 教材 (動物行為學 2011 通識) �Migratory direction is inherited by additive effects of

n ←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. →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 Ayo 教材 (動物行為學 2011 通識) 10 central and southern Africa.

Uses for compass orientation: path integration �Path integration: 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) 11 Ayo 教材 (動物行為學 2011 通識)

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 12 Ayo 教材 (動物行為學 2011 通識) 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 13 zero Ayo 教材 (動物行為學 2011 通識)

3. True navigation(真領航) �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 14 Ayo 教材 (動物行為學 2011 通識)

An animal that finds its way by using true navigation can compensate for experimental relocation and travel toward the goal. 15 Ayo 教材 (動物行為學 2011 通識)

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 16 教材 (動物行為學 2011 通識)becomes inoperative, a backup is �Ayo If one mechanism

導航與辨識方向的cues 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 17 opening �When a female wasp left the nest, she flew around the area, noting local landmarks, and then flew off in search of prey �Ayo When the ring of通識) pinecones was moved, the returning 教材 (動物行為學 2011 wasp searched the middle of the pine cone ring for the

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 18 Ayo 教材 (動物行為學 2011 通識)

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 19 almost reached the nest Ayo 教材 (動物行為學 2011 通識)

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 20 Ayo 教材 (動物行為學 2011 通識)

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 21 Ayo 教材 (動物行為學 2011 通識)

The sun follows of predictable path through the sky that 22 Ayo 教材 (動物行為學 2011 通識) 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 23 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 Ayo 教材 (動物行為學 2011 通識) 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 24 “sun” when a mirror is used to change the apparent position of the Ayo 教材 (動物行為學 2011 通識) sun Starling (歐掠鳥)

Experiments using migratory restlessness �An orientation cage has 12 25 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 Ayo 教材 (動物行為學 2011 通識) sun’s movement

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 26 Ayo 教材 (動物行為學 2011 通識)

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) 27 Ayo 教材 (動物行為學 2011 通識)

Indigo Bunting n The Indigo Bunting, Passerina cyanea, is a small seed-eating bird in the family Cardinalidae. 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. 28 Ayo 教材 (動物行為學 2011 通識)

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 29 Ayo 教材 (動物行為學 2011 通識)

The stars rotate around Polaris, the North Star. The positions of stars in the northern sky during the spring are shown here. 30 Ayo 教材 (動物行為學 2011 通識)

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 31 Ayo 教材 (動物行為學 2011 通識)

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 32 Ayo 教材 (動物行為學 2011 通識)

The orientation of indigo buntings to a stationary 33 planetarium sky after exposure to different celestial rotations. Ayo 教材 (動物行為學 2011 通識)

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 34 Ayo 教材 (動物行為學 2011 通識)

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 35 Ayo 教材 (動物行為學 2011 通識)

The sky viewed through a polarizing filter to show the pattern of skylight polarization at (a) 9 am (b) noon, and (c) 3 pm. The diagrams below show the pattern of polarization. 36 Ayo 教材 (動物行為學 2011 通識)

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 37 light beam is traveling Ayo 教材 (動物行為學 2011 通識) �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 38 Ayo 教材 (動物行為學 2011 通識)

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. n 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. 39 Ayo 教材 (動物行為學 2011 通識)

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 40 Ayo 教材 (動物行為學 2011 通識)

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 41 �Ayo Advantages to using the earth’s magnetic field as a 教材 (動物行為學 2011 通識) compass:

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 42 Ayo 教材 (動物行為學 2011 通識)

The earth’s magnetic field. 43 Ayo 教材 (動物行為學 2011 通識)

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 44 Ayo 教材 (動物行為學 2011 通識)

Birds orient using the inclination angle �In the laboratory, European robins oriented in the proper direction even without visual cues 45 Ayo 教材 (動物行為學 2011 通識)

Homing pigeons �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 n Birds that were misdirected by reversed magnetic information n 46 Ayo 教材 (動物行為學 2011 通識) 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 47 Ayo 教材 (動物行為學 2011 通識)

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 48 Ayo 教材 (動物行為學 2011 通識)

A hatchling sea turtle’s magnetic compass �Is based on the inclination of the magnetic lines of force �Similar to a bird’s compass n Hatchlings swim toward magnetic northeast in the normal geomagnetic field n 49 And continue to do so when the field is experimentally reversed Ayo 教材 (動物行為學 2011 通識)

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 50 magnetic field that they assumed while swimming into the waves Ayo 教材 (動物行為學 2011 通識) 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 51 Specific or general Ayo 教材 � (動物行為學 2011 通識)

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 52 Ayo 教材 (動物行為學 2011 通識)

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 53 Ayo 教材 (動物行為學 2011 通識)

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 54 Ayo 教材 (動物行為學 2011 通識)

Magnetic signposts in the earth’s magnetic field may direct juvenile sea turtles in the proper direction to remain within the North Atlantic gyre. 55 Ayo 教材 (動物行為學 2011 通識)

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 56 Ayo 教材 (動物行為學 2011 通識)

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. 57 Ayo 教材 (動物行為學 2011 通識)

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 58 Ayo 教材 (動物行為學 2011 通識)

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 59 Ayo 教材 (動物行為學 2011 通識)

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. 60 Ayo 教材 (動物行為學 2011 通識)

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, 61 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 教材 (動物行為學 2011 通識) �Ayo The polarity compass of bats is based on magnetite

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 lightdependent magnetoreception process, to head in the appropriate direction 62 Ayo 教材 (動物行為學 2011 通識)

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 63 Ayo 教材 (動物行為學 2011 通識)

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 64 Ayo 教材 (動物行為學 2011 通識)

A map of Hansen creek, Alaska, showing the distribution of olfactory cues in different regions of the creek area. 65 Ayo 教材 (動物行為學 2011 通識)

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 66 hatched �If they choose the wrong branch, they return to the fork Ayo 教材 (動物行為學 通識) and swim up 2011 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 67 Ayo 教材 (動物行為學 2011 通識)

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 68 the movements of bottom-feeding species (i. e. dogfish Ayoshark) 教材 (動物行為學 2011 通識)

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 69 Ayo 教材 (動物行為學 2011 通識)

小口彎頜 象鼻魚(Campylomormyrus phantasticus) 70 Ayo 教材 (動物行為學 2011 通識)

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 71 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 Ayo 教材 (動物行為學 2011 通識)

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 72 Ayo 教材 (動物行為學 2011 通識)

問題與討論 Japalura@hotmail. com n Ayo 台南 NUTN 站 http: //myweb. nutn. edu. tw/~hycheng/ 73 Ayo 教材 (動物行為學 2011 通識)