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Animal Orientation

Kineses Taxes

Migration Homing

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Orientation movements

1. Simple responses to immediate surroundings = kineses and taxes and have an immediate benefit e.g. a slater moving into a damper place.

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2. Complex movements over long distances to a pre-determined location which is out of direct sensory contact e.g. migration

and homing which are internally initiated.

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Environmental StimuliA slater retreating to a daytime crevice

could be responding to the dampness, darkness or coolness.

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Choice chambers are often used to identify which stimuli influence their behaviour.

This is a fair test where all factors are kept the same except for the one factor being

investigated.

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For a humidity investigation water is placed in one chamber and a drying

agent such as silica gel is placed in the other chamber.

Left for 20 minutes, the number in each chamber is statistically analysed.

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Simple orientation mechanisms

Taxis = movement of an organism towards or away from a stimulus.

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Positive = towards

Negative = away

Negative phototaxis = movement away from light e.g. earthworms

Positive phototaxis = movement towards the light e.g. many swimming algae

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The direction of the light source is indicated by white

rectangles.

Phototaxis, Dictyostelium giganteum

(A Cellular Slime Mold )

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Positive chemotaxis = movement towards a chemical source e.g. mosquitoes towards people along CO2 gradient

When a capillary tube filled with glucose is placed in a medium

containing E. coli, the bacteria alter their locomotion so that they

congregate near the opening of the tube.

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Positive rheotaxis = movement against a current e.g. salmon

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What does an animal do when it has a specific need, such as food, a higher humidity environment, or shelter from the sun, but it has no information about the location of the needed resource? It may engage in an undirected search, or kinesis.

Kinesis = random movement due to the presence of a stimulus. The rate of activity is determined by the intensity of the stimulus – not the direction

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stim

ulus

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stim

ulus

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This simple diagram illustrates the basics of an undirected search. The animal, travelling from left to right in the diagram, moves in a more or less straight line through unsuitable habitat. When it begins to perceive better conditions (the blue area) two things can change--its rate of speed and the angle of its turns. By turning sharper angles and slowing down, it stays in the vicinity of the improved conditions. Simple changes in movement pattern, in response to better environmental conditions, amount to habitat selection. Conversely, if an animal finds itself in poor conditions, rapid, straightline movements will increase its likelihood of finding better conditions.

http://www.animalbehavioronline.com/kineses.html

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Two types:Orthokinesis = stimulus intensity

determines speed of movemente.g. slater’s rate of movement is inversely

proportional to the humidityKlinokinesis = stimulus intensity

determines rate of turning eg lice turn more often in 35° than in 30°.

Human skin temp is about 35°.lice more likely to return to, and stay

longer in, 35°.Orthokinesis and klinokinesis movies

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Migration

= an active, regularly repeated movement in a particular direction by a population of animals

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Excludes passive dispersal (carried by the wind).

Usually to a feeding and/or breeding area.

Usually a two-way trip.

Usually have regular timing.

Often over long distances.

Often at a definite life-cycle stage

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Examples

Salmon – feed at sea and migrate up rivers to spawn. Swim up same river in which they hatched – find natal stream by its

unique chemical properties.

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Eels and whitebait swim downstream to spawn. Young swim upriver to feed and mature.

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Zooplankton twice-daily migrate 1000m vertically to feed at night and gain protection of depths during the day

http://www.wellesley.edu/Biology/Faculty/Mmoore/research_zooplankton.html

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Vertical MigrationMany freshwater and marine zooplankton perform daily excursions (i.e.,

vertical migrations) up and down in the water column, with changing levels of light triggering these daily migrations. For example, the classic pattern consists of zooplankton residing deep in the water column during

the day when light levels are high. They ascend at dusk to the surface waters where they graze on phytoplankton at night. Then, at dawn, they

descend and the daily cycle of vertical migration begins again. This behaviour most likely evolved as an anti predator strategy. The major predator of zooplankton is planktivorous fish (e.g., perch, alewives, or mackerel in the ocean). Most planktivorous fish are visual feeders and require a certain light intensity for efficient feeding. So zooplankton

avoid becoming dinner for fish by remaining in deep dark waters during the day, and ascending into dark, food-rich waters at night.

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When to migrate?

Need to know time – usually daylength measured by an internal clock

Wilson’s Plover

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Homing

= the ability of an animal to find its way home over unfamiliar territory.

Not necessarily distinct from migration i.e. salmon might be homing on natal stream

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Examples

Albatrosses wander thousands of kilometres of Southern Oceans and return every two years to NZ to breed.

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Limpets return to the same spot on a rock before low tide.

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Ecological significance of migration

Migration costs energy and runs risk of getting lost

Advantages include longer feeding time, safer breeding area, reduce intra-specific competition, kill parasites

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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

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An animal must have:a sense of direction (some form of

compass)a sense of location (understand

where it is starting from)

"Well according to the Global Positioning System we are exactly in the middle of

nowhere."

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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

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Many migratory birds have a sun compassMust allow for the apparent movement of

sun during the day – i.e. needs to know ‘the time of day’

Sun compasses

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Seasons

Summer sun

Winter sun

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Birds have a highly developed sun compass.

At the time of migration, a caged bird tends to orientate itself in the direction of

migration.

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When mirrors changed the direction of the light, birds orientated themselves relative

to the reflected sun’s rays.

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10am

Direction of

migration

90°

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3pm

Direction of

migration

180°

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10am

Direction of migration

90°

mirror

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When their internal clock was delayed, the birds orientated themselves relative to their

perceived time – not to the actual time.

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Actual time 3pm

Direction of

migration

90°

‘Bird time’ 10am

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- the Sun is not always visible

So many birds and insects can see UV light which passes through clouds.

Bees, fish and whales can even detect polarised light

Disadvantage of a solar compass

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Migration movements on an overcast day.

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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.

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The key feature is the Celestial Poles.

No internal clock needed because the direction of the Celestial Pole does not

change

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Moon compass

Sandhoppers move towards the sea using the moon’s position and an internal clock

to compensate for moon’s apparent movement

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Using earth’s magnetic fieldMany 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

A chain of magnetic particles is visible inside this bacterium. This simple compass keeps

the microscopic organisms always swimming north.

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On sunny days bar magnets made no difference.

So solar compass normally takes priority.

The influence of magnetism on pigeon homing. Pigeons were released with either a

magnet or a brass bar of the same weight on their back. On sunny days, the pigeons used the sun as a

compass and homed accurately with or without

a magnet. However, on cloudy days, the magnets disorientated the birds. Each dot represents the

birds vanishing direction. (Modified from Keeton,

1971)

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On sunny days bar magnets made no difference.

So solar compass normally takes priority.

The influence of magnetism on pigeon homing. Pigeons were released with either a

magnet or a brass bar of the same weight on their back. On sunny days, the pigeons used the sun as a

compass and homed accurately with or without

a magnet. However, on cloudy days, the magnets disorientated the birds. Each dot represents the

birds vanishing direction. (Modified from Keeton,

1971)

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A primary compass

one compass = greater accuracy.

Sun and star compasses used when possible with magnetic when it is cloudy.

Pigeons with magnets navigated better on sunny days than pigeons without on cloudy days

Sun very important as a compass

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But birds unable to see the sun as they develop could not navigate by sunlight but could on cloudy days

magnetic compasses are inborn while using the sun and stars is learned.

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Besides compasses some animals use environmental cues such as chemical

characteristics (salmon) and infra-sound of surf or wind

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Experience

Plays an important part.

Migrating birds caught and shifted.

Experienced birds corrected error. Juvenile birds continue in displaced direction

some birds seem to have an innate sense of direction but the ‘map’ needed for navigation has to be learned.

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http://bio.research.ucsc.edu/~barrylab/classes/animal_behavior/DISPERSE.HTM

http://www.monarchlab.umn.edu/Research/Mig/Migback3.html

http://www.life.umd.edu/classroom/biol106h/L23/L23_migr.html