Podcast
Questions and Answers
In animal competition, what distinguishes 'scramble competition' from 'contests'?
In animal competition, what distinguishes 'scramble competition' from 'contests'?
- Scramble competition is about acquiring resources quickly, while contests involve agonistic encounters. (correct)
- Scramble competition involves direct physical fights, while contests are based on displays.
- Scramble competition is for mates, while contests are for territories and food.
- Scramble competition is cooperative, whereas contests are always aggressive.
In escalated animal contests, the costs for participants are typically lower compared to contests involving only displays.
In escalated animal contests, the costs for participants are typically lower compared to contests involving only displays.
False (B)
Explain how an animal's tactic in a contest can influence the outcome and its fitness.
Explain how an animal's tactic in a contest can influence the outcome and its fitness.
The tactic an animal employs in a contest, such as aggression or display, can determine whether it wins the resource. Winning increases access to resources, thereby enhancing fitness and reproductive success.
The study of strategies in competitive situations, initially developed to understand human decision-making, is known as __________.
The study of strategies in competitive situations, initially developed to understand human decision-making, is known as __________.
Match the game theory concepts with their descriptions:
Match the game theory concepts with their descriptions:
What is 'frequency dependent selection' in the context of evolutionary strategies?
What is 'frequency dependent selection' in the context of evolutionary strategies?
John Maynard Smith applied game theory to animal contests, suggesting that it's always beneficial for animals to use lethal weapons in fights to ensure victory.
John Maynard Smith applied game theory to animal contests, suggesting that it's always beneficial for animals to use lethal weapons in fights to ensure victory.
Define 'Evolutionarily Stable Strategy' (ESS) and explain its significance in animal behavior.
Define 'Evolutionarily Stable Strategy' (ESS) and explain its significance in animal behavior.
In the Hawk-Dove game, a 'Hawk' strategy is characterized by always __________ and potentially injuring opponents.
In the Hawk-Dove game, a 'Hawk' strategy is characterized by always __________ and potentially injuring opponents.
According to the Hawk-Dove game, what is the primary behavior of a 'Dove' strategy?
According to the Hawk-Dove game, what is the primary behavior of a 'Dove' strategy?
In a population consisting only of 'Dove' strategists, the introduction of a 'Hawk' strategist will always be detrimental to the Hawk's fitness.
In a population consisting only of 'Dove' strategists, the introduction of a 'Hawk' strategist will always be detrimental to the Hawk's fitness.
Explain the significance of 'V' and 'C' in the context of the Hawk-Dove game.
Explain the significance of 'V' and 'C' in the context of the Hawk-Dove game.
If the value of a resource (V) is 10 and the cost of a wound (C) is 20, the fitness gain for a Hawk meeting another Hawk is calculated as $1/2V - 1/2C = $__________.
If the value of a resource (V) is 10 and the cost of a wound (C) is 20, the fitness gain for a Hawk meeting another Hawk is calculated as $1/2V - 1/2C = $__________.
According to the Hawk-Dove game with V=10 and C=20, what is the fitness gain for a Dove when it encounters a Hawk?
According to the Hawk-Dove game with V=10 and C=20, what is the fitness gain for a Dove when it encounters a Hawk?
In the Hawk-Dove game scenario where V=10 and C=20, Hawks always achieve a higher fitness gain than Doves.
In the Hawk-Dove game scenario where V=10 and C=20, Hawks always achieve a higher fitness gain than Doves.
Explain why a mixed population of Hawks and Doves can be an Evolutionarily Stable Strategy.
Explain why a mixed population of Hawks and Doves can be an Evolutionarily Stable Strategy.
For the Hawk-Dove game, the probability of playing Hawk at ESS is given by the formula $h = $__________, where V is the value of the resource and C is the cost of a wound.
For the Hawk-Dove game, the probability of playing Hawk at ESS is given by the formula $h = $__________, where V is the value of the resource and C is the cost of a wound.
If the value of the resource (V) increases while the cost of a wound (C) remains constant, what is the predicted effect on the ESS in the Hawk-Dove game?
If the value of the resource (V) increases while the cost of a wound (C) remains constant, what is the predicted effect on the ESS in the Hawk-Dove game?
If all individuals in a population adopted a 'Dove' strategy, the average payoff per contest would be lower than in a mixed Hawk-Dove ESS population.
If all individuals in a population adopted a 'Dove' strategy, the average payoff per contest would be lower than in a mixed Hawk-Dove ESS population.
Explain how the concept of ESS in the Hawk-Dove game provides evidence against 'group selection'.
Explain how the concept of ESS in the Hawk-Dove game provides evidence against 'group selection'.
Strategies where individuals are consistently either Hawks or Doves are known as __________ strategies.
Strategies where individuals are consistently either Hawks or Doves are known as __________ strategies.
What is a 'mixed strategy' in the context of the Hawk-Dove game?
What is a 'mixed strategy' in the context of the Hawk-Dove game?
In a 'pure self-assessment' model of animal contests, contestants assess both their own and their opponent's Resource Holding Potential (RHP).
In a 'pure self-assessment' model of animal contests, contestants assess both their own and their opponent's Resource Holding Potential (RHP).
Describe the 'pure self-assessment' model in animal contests and explain how it differs from the Hawk-Dove model.
Describe the 'pure self-assessment' model in animal contests and explain how it differs from the Hawk-Dove model.
In the pure self-assessment model, the 'giving up threshold' is primarily determined by the __________ of the resource.
In the pure self-assessment model, the 'giving up threshold' is primarily determined by the __________ of the resource.
Which of the following is a key characteristic of the 'mutual assessment' model in animal contests?
Which of the following is a key characteristic of the 'mutual assessment' model in animal contests?
The 'mutual assessment' model assumes a lower cognitive ability in animals compared to the 'pure self-assessment' model.
The 'mutual assessment' model assumes a lower cognitive ability in animals compared to the 'pure self-assessment' model.
Explain why 'mutual assessment' is considered a 'superior strategy' in animal contests.
Explain why 'mutual assessment' is considered a 'superior strategy' in animal contests.
Resource Holding Potential (RHP) refers to an animal's __________ ability in a contest.
Resource Holding Potential (RHP) refers to an animal's __________ ability in a contest.
According to research, what is typically a key factor determining Resource Holding Potential (RHP) in animal contests?
According to research, what is typically a key factor determining Resource Holding Potential (RHP) in animal contests?
Prior ownership of a resource is never a factor in determining the winner of an animal contest.
Prior ownership of a resource is never a factor in determining the winner of an animal contest.
Besides fighting ability, what are two other factors that can determine the winner of an animal contest?
Besides fighting ability, what are two other factors that can determine the winner of an animal contest?
The value that a contestant places on a resource is referred to as __________ Value.
The value that a contestant places on a resource is referred to as __________ Value.
Which of the following is NOT considered one of the main models of animal contests discussed?
Which of the following is NOT considered one of the main models of animal contests discussed?
In the Hawk/Dove model, assessment of the opponent's strength is a crucial component of the strategy.
In the Hawk/Dove model, assessment of the opponent's strength is a crucial component of the strategy.
Contrast the role of 'assessment' in the Hawk/Dove model versus the Mutual Assessment model.
Contrast the role of 'assessment' in the Hawk/Dove model versus the Mutual Assessment model.
Fights between two 'Hawk' strategists in the Hawk-Dove model are likely to end due to __________ or death rather than a decision to withdraw.
Fights between two 'Hawk' strategists in the Hawk-Dove model are likely to end due to __________ or death rather than a decision to withdraw.
In which model of animal contests do rivals persist in accordance with their own RHP, leading weaker rivals to give up first?
In which model of animal contests do rivals persist in accordance with their own RHP, leading weaker rivals to give up first?
The Mutual Assessment model implies a threshold for giving up that is primarily determined by the value of the resource.
The Mutual Assessment model implies a threshold for giving up that is primarily determined by the value of the resource.
Briefly explain why mutual assessment is thought to be the 'most common strategy' in animal contests by many researchers.
Briefly explain why mutual assessment is thought to be the 'most common strategy' in animal contests by many researchers.
Game theory is useful in analyzing animal contests because it helps understand how strategies are shaped by __________ selection.
Game theory is useful in analyzing animal contests because it helps understand how strategies are shaped by __________ selection.
Which of the following scenarios best illustrates scramble competition among animals?
Which of the following scenarios best illustrates scramble competition among animals?
In contests involving escalated fights compared to displays without contact, the potential costs for the participants are generally lower.
In contests involving escalated fights compared to displays without contact, the potential costs for the participants are generally lower.
Explain how the understanding of animal contests contributes to the broader comprehension of natural selection.
Explain how the understanding of animal contests contributes to the broader comprehension of natural selection.
The Prisoner's Dilemma in game theory demonstrates that under specific payoff conditions, the most rational choice for an individual, known as the ______, is to confess, even if mutual cooperation would yield a better outcome for both parties.
The Prisoner's Dilemma in game theory demonstrates that under specific payoff conditions, the most rational choice for an individual, known as the ______, is to confess, even if mutual cooperation would yield a better outcome for both parties.
Match the following terms related to animal contests and game theory with their descriptions:
Match the following terms related to animal contests and game theory with their descriptions:
In the Hawk-Dove game, if the cost of a wound (C) increases significantly while the value of the resource (V) remains constant, what is the most likely effect on the Evolutionarily Stable Strategy (ESS)?
In the Hawk-Dove game, if the cost of a wound (C) increases significantly while the value of the resource (V) remains constant, what is the most likely effect on the Evolutionarily Stable Strategy (ESS)?
According to the Hawk-Dove model, fights between two 'hawk' strategists typically conclude with a decision based on mutual assessment rather than potential injury.
According to the Hawk-Dove model, fights between two 'hawk' strategists typically conclude with a decision based on mutual assessment rather than potential injury.
Distinguish between a 'pure strategy' and a 'mixed strategy' in the context of game theory as applied to animal contests.
Distinguish between a 'pure strategy' and a 'mixed strategy' in the context of game theory as applied to animal contests.
In the context of animal contests, Resource Holding Potential (RHP) is best defined as an animal's inherent ______ ability, which often determines its likelihood of winning a physical confrontation.
In the context of animal contests, Resource Holding Potential (RHP) is best defined as an animal's inherent ______ ability, which often determines its likelihood of winning a physical confrontation.
Which of the following factors is NOT typically considered a primary determinant of the winner in animal contests, as highlighted in the context of game theory and contest models?
Which of the following factors is NOT typically considered a primary determinant of the winner in animal contests, as highlighted in the context of game theory and contest models?
Flashcards
Animal competition resources
Animal competition resources
Limited resources animals compete for include food, territories, nest sites and mates.
Scramble competition
Scramble competition
Competition where the first to get the resource takes it.
Contests
Contests
A form of competition that takes the form of agonistic encounters.
Tactics in contests
Tactics in contests
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Importance of contests in natural selection
Importance of contests in natural selection
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Game theory
Game theory
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Prisoner's dilemma
Prisoner's dilemma
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Frequency dependent selection
Frequency dependent selection
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Evolutionarily stable strategy (ESS)
Evolutionarily stable strategy (ESS)
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Hawk strategy
Hawk strategy
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Dove strategy
Dove strategy
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Hawk and Dove: Encounters
Hawk and Dove: Encounters
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V
V
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C
C
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Mutual assessment
Mutual assessment
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Outcome of mutual assessment
Outcome of mutual assessment
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Game theory
Game theory
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Costs of the fight
Costs of the fight
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Another factor in winning a contest
Another factor in winning a contest
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Pure self assessment
Pure self assessment
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Hawk Dove Model: assessment?
Hawk Dove Model: assessment?
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Study Notes
- Animal contests relate to the key concept of evolutionarily stable strategies
Competition
- Animals compete for limited resources like food, territories, nest sites, and mates
- Scramble competition is when the first to get the resource takes it
- Contests take the form of agonistic encounters
Contests
- Displays may occur without contact, but can also involve escalated fights, or both
- Both displays and escalated fights have costs
- Escalated fights are likely to be more costly
- Animals use different tactics in contests which can influence the outcome of which contestant wins
- Understanding contests is important because they determine fitness and drive natural selection
Game Theory
- Game theory studies strategies
- Economists initially developed game theory
- Game theory was to study rational human decision-making
- The prisoner's dilemma is the most studied game in game theory
- The best choice in payoff conditions is to confess, also known as the Nash Equilibrium
- In frequency dependent selection, the best strategy depends on what others in the population are doing
Applying Game Theory
- John Maynard Smith applied game theory to animal contests
- Contests often occur in a restrained fashion, where lethal weapons are not always used such as poisonous snakes
- Fitness gain from different strategies for individuals can be analyzed by applying frequency dependent selection and game theory
Definitions
- Frequency dependent selection is where the direction of selection depends on which options are used in the rest of the population
- Evolutionarily Stable Strategy (ESS) is a strategy that, if all members of a population adopt it, cannot be bettered by an alternative strategy
- A strategy is a mode or option that is genetically determined
The Hawk-Dove Game
- It explains two strategies used in animal contests
- Hawk: Always fights and may injure opponents
- Dove: Only displays and never engages in fights; will run away immediately if attacked to avoid injury
- The better option depends on the context of the contest
Hawks and Doves
- Imagine a population of doves in which a mutant hawk is produced
- Hawks will win all encounters because their attacks cause the dove to run away
- If the mutant allele spreads (hawks get the resources), hawks will start to encounter other hawks
- The encounters between hawks can lead to injuries
Considering Value and Cost
- Value of the resource is V
- Cost of a wound is C
Fitness Gain
- Fitness gain depends on the opponent type
- Hawk vs Hawk: 1/2v-1/2c
- Hawk vs Dove: V
- Dove vs Hawk =0
- Dove vs Dove = 1/2v
Arbitrary Values
- An example uses arbitrary values for fitness units
- V = 10
- C = 20
- Hawks do well when they meet doves (+10) but fare poorly when they meet other hawks (-5)
- Doves achieve a higher fitness gain when they meet a hawk (0) compared to a hawk meeting another hawk (-5)
- Doves meeting other doves perform better (+5) than when they encounter hawks (0)
- A population mix should occur when the two strategies perform equally well
Calculating the ESS in the Hawk-Dove Game
- At ESS fitness payoff of playing Hawk = fitness payoff of playing dove
- Play hawk with probability h, therefore play dove with probability 1-h
- (1/2v – 1/2c)h + v(1-h) = 0h + (1/2v)(1-h)
- 1/2vh – 1/2ch +v – vh = 1/2v – 1/2vh
- vh – ch + 2v – 2vh = v – vh
- v = ch
- v/c=h
- h=v/c
- 1-h = 1 – (v / c)
- Play Hawk with probability V / C = 10 / 20 = 1 / 2 = 50%
- Play Dove with probability 1-(V / C) = 1 / 2 = 50%
- Average payoff per contest at ESS is 2.5
- If all had been Doves, payoff would have been 5
- This is evidence against group selection
Variation in Costs and Benefits
- The ESS is for an arbitrary set of values
- This allows to see the changes when the values are altered
- If V is increased from 10 to 15, keeping other values the same, ESS is now for 75% hawks
- If V is increased further to 20, ESS is for the whole population to comprise hawks
- With high value resources, doves may be eliminated from the population
- If C is increased from 20 to 30, keeping other original values the same, ESS shifts to 33% hawks
- As C increases, the utility of fighting decreases
Mixed Strategies
- Pure strategies include individuals being either hawks or doves
- Mixed strategy: Play Hawk with probability x and Dove with probability 1-x
- These probabilities will have the same frequencies as set by the ESS calculation for particular costs and benefits
Information Gathering
- If the values change, they act upon the ESS in the Hawk-Dove game by natural selection
- There is no information gathering prior to a contest in this game
- Contestants should gather information whenever it is likely to favorably influence the pay-off from the fight
- Important information includes potential or actual costs of the fight (opponent) and potential gain (resource value)
Winner Determination
- Differences in fighting ability, termed Resource Holding Potential (RHP), typically favor the larger animal
- Prior ownership of the resource sways the outcome
- Resource value influences the determination
Main Models
- Hawk/Dove Model
- Pure Self Assessment Model
- Mutual Assessment Model
Hawk / Dove Model Explained
- There is no assessment in the Hawk / Dove Model
- The ESS of hawks / doves in the population is determined by natural selection
- Fights between two hawks end as a result of injury or death rather than a decision
Pure Self Assessment Model Explained
- Each contestant has information about its own abilities or state
- No assessment of the opponent occurs, and costs are not influenced by the opponent
- Costs increase as the fight progresses, and when a threshold is reached, the animal gives up
- Rivals persist in accord with their own RHP such that the weaker rival will reach their limit and give up first
- The giving up threshold is determined by the value of the resource
Mutual Assesment Model Explained
- This assumes that animals know their own condition / abilities and animals gather information about the opponent
- Each contestant compares its perception of its own ability with that gathered about the opponent
- The weaker animal gives up when it has sufficient information to make this decision
- No threshold is implied in this model
- A much higher cognitive ability is assumed
- Mutual assessment may occur prior to escalation and may be a superior strategy because potential losers can avoid the cost of fighting in contests they would eventually lose
- This is assumed by many authors to be the most common strategy
Learning Objectives
- Understand the role of game theory in furthering our understanding of animal contests
- Understand the concept of an Evolutionarily Stable Strategy (ESS)
- Understand the Hawk-Dove model
- Know about contest asymmetries and assessment strategies
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