Habitat Choice & Migration Part 1

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Ultimate causation question of habitat choice & migration?
What determines the range of species in which a species occurs?
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Proximate causation question of habitat choice & migration?
How does each individual determine when it's an appropriate habitat?
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What is Ideal Free Distribution?
Describes how individuals should distribute themselves in an ideal world.
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What violations of the assumptions are there?
Dominant individual can monopolise access to high quality patch.
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When should animals invest in territorial defence?
When they cannot distribute themselves evenly, due to territorial behaviour.
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Costs of territoral defence?
Time, energy, risk of aggression.
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Benefits of territoral defence?
Can use resources without interference. Food resources.
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In what circumstances would free movement be discouraged by territoral behaviour?
When individuals are trying to monopolise high quality sites.
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At what point does territoral expansion occur?
When fitness costs outweigh risks.
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What is the role of testosterone in territoral behaviour?
Makes animals wanting to engage in territoral expansion more. Makes males hyperterritoral.
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What are the disadvantages of high testosterone but no food?
More mortalities. Spend more time fighting, not feeding = more deaths. Can be counteracted by being given food.
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Example of study that showed this?
Lizards given implant.
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When does peaceful coexistence occur?
When benefits of exclusive ownership of resource do not outweigh costs.
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Can males coexist?
Yes, but in many cases, this is only outside of breeding season. E.g. Spiny Lizards.
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What is facultive aggression?
Ability to adjust aggression up and down. Depends on situation and time.
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What happens when individuals vary in their territory-holding abilities?
Strongest competitors should be found in best territories.
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What happens when a dominant male gains net benefit from investment in territoral aggression?
Should be apparent in survival/reproductive advantages.
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Example of this happening?
Birds - 2 different forests. One high quality, the other low quality. More energy reserves = leave for mating grounds sooner. Do not produce as many offspring in low quality forests.
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Why do animals give up quickly when fighting for a territory?
Evolutionary Stable Strategy - avoid injury. Rule - resident always wins and intruder gives up. Mutant strategy = lead to injury from tough fights.
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Evidence for 'resident always wins' rule?
Butterflies. White = resident male. Black tries to intrude, white always wins.
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Limitations of that study?
Capture could cause stress/exhaustion.
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Limitations of that study?
Capture could cause stress/exhaustion. When repeated = original resident wins.
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What are nonarbitrary rules of who wins contests?
Winners normally have an 'edge' e.g. strength, size.
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Being larger does not always mean winning contests, what's a species that this does not apply to?
Birds - epaulette signals intrinsic feature.
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Being larger does not always mean winning contests, what's a species that this does not apply to?
Damselflies - more fat reserves. More energy reserves to outfly rival.
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What are the factors which affect success in contests?
Size/strength, intrinsic features, energy reserves, motivation (older residents - more persistent), resource value.
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What is the 'Dear Enemy' Effect?
Over time, disputes with neighbours get settled. Little energy expendature once disputes settled. Intruder has to engage in fights = resident has more to lose than intruder to gain.
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What is disperal?
One time event. Species grow up in location, disperse when mature.
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What is migration?
Form of disperal, involving animals leaving territory then returning in cyclic fashion.
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You can use cost-benefit approach to understand why....happens?
Dispersal and migration.
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Limitations of disperal and migration?
Energetic costs and risk of predation.
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Advantages of dispersal?
Reduces inbreeding. Carry recessive alleles, inbreeding increases chances of offspring carrying 2 recessive alleles = bad consequences.
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Example of recessive alleles having bad outcomes in humans?
HFE Gene. Regulates absorption of iron into blood. 2 copies = homochromatosis (iron overload).
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Benefits of migration?
Food, survival and breeding opportunities.
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Why do animals migrate for food?
Away from the equator = longer days, food more abundant, more rich prey/plants. More food opportunities.
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What types of animals does this happen in?
Insects, mammals, fish and sea turtles.
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Example of an animal that migrates to breed?
Monarch butterfly. Not same generation returns, but do migrate back.
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How did extreme migrations start?
Tropical bird species - short trips.
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Costs of migration?
Extra weight needed (energy reserves to make journey), risk of death (over water), physiological and metabolic changes.
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What does some migration in birds sometimes depend on?
Long journeys = finding food on the way. Impaired by factors e.g. humans fishing = less horse shoe crab eggs.
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Do birds make decisions about the risk of mortality when deciding whether to migrate?
Yes. Those with low fat reserves are less likely to embark on long journeys. Or choose different flight path.
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What studies can you conduct to look into which way birds want to fly?
Funnel with ink on inside - see which direction birds fly out of funnel.
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What have findings shown?
Low fat reserves fly west (across water) - shorter journey.
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Example of an animal that migrates for survival?
Butterflies - would freeze to death if they stayed put.
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What are conditional migration strategies?
Animals that can switch from being migratory or non-migratory = a CONDITIONAL STRATEGY
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Example of a study that showed this?
Blackbirds - can choose.
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What are conditional strategies based on (deciding whether to migrate or not)?
Status - social dominant individuals decide for the species whether to migrate or not. Force subordinates to follow instruction.
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What are predictions made my conditional migration strategies?
Blackbirds should be able to switch tactics. Dominant individuals should decide best tactic with biggest pay off. When choosing freely, birds should adopt best tactic with biggest pay off.
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Other cards in this set

Card 2

Front

Proximate causation question of habitat choice & migration?

Back

How does each individual determine when it's an appropriate habitat?

Card 3

Front

What is Ideal Free Distribution?

Back

Preview of the front of card 3

Card 4

Front

What violations of the assumptions are there?

Back

Preview of the front of card 4

Card 5

Front

When should animals invest in territorial defence?

Back

Preview of the front of card 5
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