Transcript lecture7.html

Observational Learning
• The individual learns from others. Social
learning may occur by watching the
behaviour of another, but it may also occur
by simpler means.
Observational learning in Japanese macaques
The habit of washing
sweet potatoes in the sea
started with a young
Japanese macaque
female. It spread rapidly
to other members of the
troop.
Lecture 7. Foraging and Migration
Optimal Foraging
An optimality model for a hypothetical behaviour. According to
optimality theory an optimal alternative evolves that maximizes the
difference between the cost and benefit and, thus, maximizes fitness.
Handling of food by American
crows
• English walnuts break
easily, black walnuts do
not
• Walnuts crack more easily
on hard surfaces
• Walnuts are increasingly
likely to crack with each
successive drop
• Crows feed in large flocks
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Proximate explanation: it makes them taste better
Ultimate explanation: adding spices to food inhibits
the growth of microorganisms and thus protects us from disease.
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The migratory route of the arctic tern (Sterna paradisea)
Costs of migration
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Energy expenditure
Risk of exposure to severe weather
Predation
Competition for territories
Advantages of
migration
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Greater food supply
Special conditions for breeding
Reduction in parasitism
Reduction in competition
for resources
Migratory routes of green sea
turtles (Chelonia mydas)
Navigation
Processes that enable an animal to find its
way from one specific place to another
• Piloting
• Compass orientation
• ‘True’ navigation
Piloting
The ability to find a goal by referring to
familiar landmarks
Compass orientation
The ability to head in a geographical
direction without the use of landmarks.
Experimental relocation of an animal that is using compass orientation
causes it to miss the goal by the amount of its displacement
Compass orientation in the European starling
Navigation in the desert ant (Catahlyphis
bicolor)
Navigation by dead reckoning
The animal determines its position by using the direction and
distance of each successive leg of the outward trip.
A compass can then be used to steer a course directly toward home.
“True” navigation
• Reference to a goal is established regardless
of its location without the use of landmarks
An animal that finds its way by using true navigation can compensate
for experimental relocation and travel toward the goal. This implies
that the animal cannot directly sense its goal and that it is not using
familiar landmarks to direct its journey.
A famous homing pigeon
Two hundred fifty American soldiers in World War I owed their lives
to this homing pigeon, which carried a distress message to its handler.
Reinforcements were sent to rescue the beleaguered battalion.
Gustav Kramer’s sun-compass
orientation experiment
Birds use the sun as a navigational cue
Using mirrors, Kramer altered the apparent position
of the sun. The birds shifted their migratory direction
by the same angle
Birds compensate for the sun’s
apparent motion
Caged starlings alter the direction of their attempted
migratory movement with respect to the artificial sun,
as if assuming that the ‘sun’ is moving.
Stars as visual cues in navigation
The stars rotate around Polaris, the North Star. The center of rotation of the stars
tells birds which way is north. The positions of stars in the northern sky during
the spring are shown here. The closed circles indicate star positions during
the early evening, and the open circles indicate the positions of the same stars
six hours later.