Economic Decisions (C3) & Arms Race (C4) Flashcards
1
Q
Optimization analysis?
A
= deals with what food items should an optimal foragers eat.
2
Q
How to measure adaptive value? (2)
A
• Contribution to survival & reproduction (not practical).
• Immediate nutritional energy gain (important).
3
Q
Eg of optimization analysis?
A
Shrews.
4
Q
What diet selections models do we focus on? (2)
A
• Optimal Foraging Theory.
•
5
Q
Handling time?
A
= the amount of time it takes a forager to capture, handle & chew prey.
6
Q
Profitability of each food item equation?
A
P = E/h.
7
Q
P = E/h symbols? (3)
A
• P = Profitability.
• E = Currency.
• h = handling time.
8
Q
In what instance does the optimal forager feed on the less preferred food type?
A
When the profitability of the two food types is the same.
9
Q
Why would the Profitability of the two food types be the same? (2)
A
• Due to the addition of a search time to the preferred food type.
• Increased search time for the preferred food type.
Therefore, optimal forager will eat less preferred food type on its way to most preferred food type.
10
Q
Which food will be the most preferred/the one that the forager will eat?
A
Food type with the highest Profitability.
11
Q
Eg of Profitability equation (Lay it out for me)? (5)
A
● Food 1:
E = 10.
h = 5.
Therefore, P of food 1 = 10/5 = 2.
● Food 2:
E = 5.
h = 5.
Therefore, P of food 2 = 5/5 = 1.
● Optimal forager should only eat Food 1 (preferred).
● If Food 1 becomes scarce & search time increases then:
× Food 1
E = 10; h = 5; s = 5.
Therefore, P of food 1 = E/(h+s) = 10/(5+5) = 1.
× Food 2:
E = 5: h = 5.
Therefore, P of food 2 = 5/5 =1.
● Optimal forager will eat both food types.
12
Q
Considerations regarding profitability of foods? (3)
A
• Search time.
• Handling time.
• Physical constraints.
13
Q
General equation of Profitability?
A
P = Energy of prey item/ Time take to acquire prey item.
14
Q
Egs of physical constraints? (3)
A
• Size of prey.
• Maximum size processing.
• Minimum size threshold.
15
Q
Symbols of equation? (5)
A
• E = energy provided by prey.
• h = handling time.
• s = searching time.
• T = total time taken to acquire prey item (h+s).
• P = Profitability.
16
Q
Things to note regarding Profitability? (3)
A
• High quality prey always gets eaten.
• Lower quality prey only gets eaten when gain from eating > gain from rejecting & searching for preferred food.
• Less quality food inclusion depends on the abundance of highest quality food.
17
Q
If e2/h2 > e1/ (s1 + h1) then…?
A
Forager eats both foods.
18
Q
If e2/h2 < e1/ (s1 + h1) then…?
A
Forager eats food 1 only.
19
Q
Optimal foraging theory predictions? (4)
A
• Rank order of the preferred food item depends on the amount of energy & time taken to obtain it.
• Whether a particular food is eaten or not depends only on the availability of the most preferred food types.
• Diet widens as the abundance of the preferred food type decreases.
• Food types should be accepted or rejected in an all-or-nothing basis.
20
Q
Is 1st OFT prediction supported?
A
Not always supported.
21
Q
Why is 1st OFT prediction not always supported?
A
It’s because the currency could be different to energy (i.e., it’snot always energy).
22
Q
Egs that shows 1st OFT prediction is not always supported? (2)
A
• Starlings.
• Bees.
23
Q
Is the 2nd OFT prediction supported?
A
Not always supported.
24
Q
Why is the 2nd OFT prediction not always supported?
A
It’s because the OFT only considers interspersed food & not when food types are patchy/have patchy distribution.
25
Is the 3rd OFT prediction supported?
Always supported.
26
Is the 4th OFT prediction supported?
No.
27
Why is the 4th OFT prediction not supported at all?
It's because animals generally show partial preference.
28
Egs of 4th OFT prediction not being supported? (2)
• Crows.
• Oystercatchers.
29
Eg of OFT?
Experiment with great tit (Parsus major).
30
Explain experiment of great tit (Parsus major)? (2)
• Large worms (Prey 1) and small worms (Prey 2) were placed on a moving belt.
• Varying distances between large worms = varying search time.
31
Why might the all-or-nothing OFT prediction be wrong? (5)
• Food items might vary in quality.
• Random variability in encounter rate.
• Value of food type varies over time.
• Simultaneous encounter with 2 food types.
• Other behavioural constraints (predation, competition).
32
What do you mean when you say Random variability in encounter rate?
We mean that there's uncertainty regarding when or where the next meal might come or be.
33
Optimal decision rule?
= decision that maximizes the currency under the constraints of the environment.
34
Egs of Optimal decision rules?
• Optimal size of a food item that an animal should feed on.
35
Egs of OFT? (2)
• Crows feeding on clams.
• Oystercatchers & clams.
36
Explain Crows & clams? (4)
• Search time = 4 × flight time.
• If too choosy, they wander across rejecting too many small clams.
• If not choosy enough, waste lots of time feeding on small clams that take too much time to open relative to the small content of clam.
• Probability of the clam breaking is independent of size.
37
Factors to consider when deciding how long a forager should stay in a patch? (3)
• Distance between patches.
• Food in each patch.
• How long it will to feed in each patch.
38
Scenario of Marginal Value Theorem (MVT)? (3)
• As you pick fruits from a tree, energy gain starts to decrease when apples become less on the tree.
• Take longer & longer to find more apples.
• Do you keep looking or do you move to another tree?
39
Loading curve/Gain curve?
= curve of diminishing returns.
40
Aim of loading curve?
To maximize net rate of food intake while taking into account travel time between patches.
41
What is the maximum rate of energy gain on the gain curve?
The line that hits the gain curve at a tangent (steepest slope).
42
Longer time/distance between patch =...?
More time in patch.
43
Shorter time/distance between patch = ...?
Less time in patch.
44
Shorter time/distance between patch = ...?
Less time in patch.
45
Constraints?
= factors that can limit the forager's ability to maximize the currency.
46
Egs of constraints? (3)
• Time it takes from nesting site to foraging site.
• Maximum number of food items a forager is able to carry back to its nesting site.
• Limits to learning & memory.
47
Minimum size threshold?
= the point at which consuming the prey becomes profitable.
48
If Food item > Minimize size threshold?
= food item in the environment is consumed.
49
If Food item < Minimum size threshold?
= food item in environment is rejected.
50
What does the minimum size threshold depend on? (2)
• Search time.
• Handling time.
51
Paper of Crows & clams?
52
Explain Oystercatchers & clams? (2)
• Easier to break small clams than large clams.
• Use bills to open small clams.
53
Paper on Oystercatchers & clams?
54
Why do you think there is no clearest rejection vs acceptance but always only partial preference?
55
Optimal Foraging Theory (OFT)?
= behavioural ecology model that helps predict how an animal behaves when searching for food.
56
OFT use?
Helps us predict the best strategy that an animal can use to maximize benefits over costs.
57
Marginal Value Theorem (MVT)?
= involves the decision of how long one should stay in a patch before moving to the next patch.
58
MVT attributes? (4)
• Limitation of the OFT.
• Search time for both food types becomes independent.
• Patchy food distribution.
• Summarized through the Gain curve.
59
Eg of MVT?
Foraging behaviour of Starlings.
60
Predictions of MVT? (2)
• Allows you to predict optimal time in a patch if you know the travel time & gain curve.
• More patches, less time per patch.
61
Assumptions of the MVT? (3)
• Resources are patchy at the spatial scale of forager movements.
• Maximum fitness = maximize long term rate of energy intake.
• Choosing among two patches available at once (simultaneously).
62
MVT constraints? (2)
• Travel time.
• Shape of the curve of diminishing returns.
63
MVT applications?
64
Eg of MVT & Reproductive decisions?
Dung flies.
65
Explain Dung flies?
66
Explain Dung flies in terms of Curve of diminishing returns?
67
What do differences in currency of Bees & Starlings show us? (2)
• How to use economic costs vs benefits analysis to compare alternative currencies.
• How to use economic costs & benefits analysis to understand why a certain currency is appropriate in each case.
68
Things to note regarding models? (3)
• Although they have been used to predict the currency an animal would use, it doesn't mean that animals do the same.
• Animals follow rules of thumb (maybe based from experience).
• Animals have to always assess their environment & re-evaluate their decisions at each step.
69
Egs of different currencies? (4)
• Energy net gain.
• Net intake to the young.
• Energy efficiency.
• Risk of starvation.
70
Energy net gain?
= energy content of food item.
71
Net intake to the young?
= flight distance to young.
72
Energy efficiency?
= extends their lifespan & nectar quantity.
73
Risk of starvation attributes? (5)
• Affects an animal's ability to be risk-prone & risk-averse.
• Perceived benefit (utility).
• Animal sensitivity to two things.
• Risk prone behaviour.
• Risk averse behaviour.
74
Risk prone?
= prepared to gamble.
75
Risk averse?
= rather go with the less variable reward.
76
Risk prone behaviour attributes? (2)
• Energy requirements > Average expected reward.
• More variable options.
77
Risk averse behaviour attributes? (2)
• Energy requirements < Average expected reward.
• Less variable options.
78
Egs of Risk starvation? (2)
• Yellow-eyed Juncos.
• Shrews.
79
Explain Shrews example under Risk of starvation? (3)
• High energy remand.
• Expected to be choosy about food source.
• Become risk prone when in a physiologically depleted state.
80
Egs of constraints for dynamic models? (3)
• Risk of predation.
• Hunger state of an individual.
• Nutrient requirements.
81
Impacts of constraints for dynamic models? (2)
• Change the way a forager makes a decision.
• Have a consequence on the habitat used by certain individuals & eventually affect the community.
82
Central place foraging?
=
83
Central place foraging attribute?
Deals with the economics of carrying a load.
84
Costs of central place foraging? (2)
• Energy getting to feeding area.
• Energy returning from feeding area while carrying load of food.
85
Egs of central place foragers? (2)
• Starlings.
• Bees.
86
Explain the economic decisions of Starlings?
87
Explain the economic decisions of Bees?
88
How we get the curve: Starlings? (3)
NB: isp = is proportional to
● Size of load (isp) Rate of delivery of food (isp) Survival of young (isp) Reproductive success.
● 1st prey = returned easily.
Last prey = returned less easily (prey already in beak).
● Yields "Loading curve".
89
Central place foraging spectrum?
• Left = Give up too early — spend time in
• Right = Give up too late — spend time in ineffective search.
90
Factors determining the rate that colonies gain energy? (2)
• Availability of flowers.
• Distance of flowers.
91
Starlings vs Bees? (3)
• Different currencies.
• Rate of return per unit time (short term).
• Rate of return per worker (long term) [maximize energy collected/expended].
92
Starlings vs Bees in terms of currencies?
● Starlings = net intake to the young.
● Bees = energy efficiency.
93
Egs of rules of thumb/giving up rules? (3)
• Fixed effort.
• Fixed time.
• Giving up time (GUT).
94
Giving Up Time (GUT)?
= based on the idea of how long being in a patch increases with more food in the patch.
95
Egs of GUT? (2)
• Sit & wait predator: GUT = 0.5hrs.
• Time between successive prey arrivals: 0.1, 0.4, 0.2, 0.7, 0.1hrs.
96
Adaptive value of risk-sensitivity & threat of starvation attributes? (5)
• Switch from risk prone to risk averse (when facing risk of starvation).
• Animal is risk sensitive in its foraging behaviour.
• Environment cues.
• Perceived value of the reward to the animal.
• Variability in searching time.
97
Environmental cues?
= anything that predicts future increases in energy demand.
98
Egs of Environmental cues? (2)
• Lack of rainfall.
• Low temperatures.
99
Egs of animals regarding trade-offs in foraging & danger/predation risk? (2)
• Squirrels.
• Bluegill sunfish.
100
Explain Squirrels?
101
Explain Bluegill sunfish?
102
Static optimization models vs Dynamic models? (1)
● Static optimization models
= external constraints only (little consideration for physiology of forager).
● Dynamic models
= internal & external constraints.
103
How does foraging behaviour influence population & community ecology?
104
Argue the importance of understanding foraging decisions as a driver of biodiversity?
105
How does distance between patches influence the time spent in a patch?
106
Given the same distance between patches, how does the patch food availability influence time spent per patch?
107
How can bee & starling central place foraging be described through an optimal foraging graphical model?
108
What are the currencies that optimal foragers use? Is there a single currency used by everyone?
109
How can the hunger state of an animal or predation risk constrain optimal decision rules?
110
Things to note about MVT? (3)
• High density patch = short distance, less time.
• Low density = long distance, more time.
• Same patches = one curve, not two.
111
Why is investigating foraging behaviour so important?
It's because it links to the other levels of ecological organization (trophic cascade).
112
OFT applications? (2)
• Criminology.
• Cancer research.
113
Eg of Importance/Application of understanding individuals foraging needs in conservation & management?
Research project on Sable antelope in Kgaswana Mountain Reserve through identifying the factors influencing habitat use (fires) & ecological requirements of sable populations, & using that information to manage them better.
114
High vigilance benefits vs costs? (2)
● Benefit
= higher probability of detecting predator.
● Cost
= lower food intake.
115
FitzGibbon paper summary? (4)
● Predicted that gazelles that spent less time being vigilant were more vulnerable to predation.
● When observing 2 gazelles it was discovered that the cheetah would often target the less vigilant gazelle.
● Therefore, the less vigilant you are, the slower you tend to be in fleeing quickly & less vigilant individuals may have poor physical conditions.
● Shows the importance of vigilance & the costs of lacking it.
116
Bedriekoff & Ritter 1994 summary? (3)
● Talks on benefits of bunching close together on vigilance in Nxai Pan Springbok.
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●
117
Underwood 1982 summary? (3)
● Speaks on the effect of body size & habitat type on the vigilance behaviour in grazing African antelopes.
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●
118
Owen-Smith et al 1983 summary? (3)
● Speaks on the effect of forage quality & availability on vigilance in kudus.
●
●
119
You et al 2021 summary? (3)
● Speaks on the effect of forage quality & availability in vigilance in zebras & wildebeest.
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●
120
Pros/Roles of large group size? (4)
• More eyes.
• Dilution effect.
• Bunching close together.
• Group defence.
121
Explain More eyes?
Large group size, Less time for each individual to be vigilant.
122
Explain Dilution effect? (3)
• Based on the probabilities of being targeted by the predator.
• Large group size, Low P (of being eaten).
• "Diluted" into the population😂
123
Explain Bunching close together? (2)
• Large group size, More confusion to predator as he/she can't spot who their target is.
• Individuals at edges more vigilant & more at risk than individuals in the centre.
124
Explain Group defence?
Large group sizes are able to fight off predators with much success.
125
Role of body size on vigilance? (2)
• Large body size, Less predation risk, Less vigilance.
• Works better in groups.
126
Role of habitat type on vigilance?
Tall grasslands/Closed woodlands, High predation risk, High vigilance (compared to open fields).
127
Role of forage quality & availability on vigilance? (2)
• High vigilance in wet season as feed on grass with head down.
• Low vigilance in dry season as feed on trees with head up.
128
Role of day & night on vigilance? (2)
● More feeding during day, High predation risk, High vigilance.
But because of global warming/climate change with its extremely high temperatures...
● More feeding at night even though predation exists (low).
129
Kinds of Prey responses? (3)
• Running.
• Hiding.
• Alarm signaling.
130
Why are Hiding & Running not good/optimum prey responses? (3)
• Costs energy.
• Loss of feeding time.
• Leaving behind a potential favourable area.
131
Which prey response is the best/most optimal?
Alarm signaling.
132
Why is alarm signaling the most optimum prey response? (2)
• Alerts predator that it's been spotted.
• Alerts the rest of the group that a predator is in the vicinity.
133
Is sounding an alarm call an altruistic/selfless behaviour?
No, because if the animal left quietly, it would be left all alone & insecure.
134
P = E/ (h+s) attributes in terms of evolutionary arms race? (2)
• Used to apply the arms race through increasing/decreasing the handling & search times.
• Adaptations by the prey to increase h or s to decrease its chances of the predator finding them.
135
Evolutionary arms race?
= a continuous loop of the counter-adaptations of prey & predator.
136
What cartoon does the Evolutionary arms race remind you of?
Tom & Jerry.
137
How does crypsis benefit prey? (2)
• Increases survival.
• Decreases predation risk.
138
Crypsis?
= avoiding detection by other organisms.
139
Different adaptations? (3)
• Crypsis.
• Startle predators.
• Aposematism.
140
Types of crypsis? (4)
• Background matching.
• Disruptive colouration.
• Counter-shading.
• Masquerade.
141
Background matching?
= use camouflage to blend in with the background environment & avoid detection.
142
Eg of Background matching?
Chameleons.
143
Disruptive colouration?
= body patterns that break up the body outline.
144
Disruptive colouration experiment? (4)
● Bird was placed in front of a screen with images of either a moth against a contrasting background or a moth that had Disruptive colouration.
● Next to the bird was a red buzzer for the bird to press it if it detected no moths on an image.
● When the bird detected moths against contrasting backgrounds, it pecked at the screen, but when it didn't it pressed the red buzzer.
● It was found that moths displaying disruptive colouration survived better, therefore proving this crypsis type to be beneficial.
145
Counter-shading?
= when an organism is lighter on its ventral side & darker on its dorsal side/upper part, which makes the animal appear flat & more cryptic.
146
Eg of Counter-shading?
Sharks/Aquatic animals.
147
Masquerade?
= where individuals resemble inedible objects.
148
Startling a predator attributes? (3)
• Eyes on butterfly wings.
• Increases h (benefits prey).
• With more exposure, decreases h (benefits predator).
149
Aposematism/Aposematic colouration?
= an anti-predator adaptation in which a warning signal is associated with the unprofitability of a prey item to potential predators.
150
Aposematism attributes? (2)
• Warning colouration.
• Beneficial to both predator & prey.
151
Eg of Aposematism?
Coral snakes.
152
How does an Evolutionary arms race start? (3)
• Uses P=E/(h+s) to demonstrate how arms race works.
• Anything that increases h & s (beneficial to prey).
• Anyhthing that decreases h & s (beneficial to predator).
153
Why hasn't the one (predator or prey) led the other one (prey or predator) to extinction? (3)
• Prudent predation.
• Group extinctions.
• Prey are ahead.
154
Prudent predation?
= predator makes sure to not eat all the prey & leave some for tomorrow (human-centered).
155
Group extinctions?
= unstable systems might have gone extinct.
156
Prey are ahead? (2)
• Life-dinner principle.
• Shorter generation time.
157
Explain the Life-dinner principle?
Where prey is running for its life, while a predator is running for its dinner & may live to see another day if it doesn't catch its prey however, the prey may not if its caught by the predator.
158
Explain Shorter generation time?
Speaks to the fact that prey have shorter generation times and are thus forced to adapt quicker/evolve quicker (high selection pressure on prey).
159
Eg of Shorter generation time?
Birds vs Insects.
160
Why don't predators become so efficient that they drive prey to extinction?
It's because predators are not optimum enough to specialize on one type of prey & thus feed on many prey species.
161
Why don't prey evolve such perfect counter-adaptations that the predators become extinct?
If prey had perfect counter-adaptations they would have no selective pressure that forces them to maintain & improve those counter-adaptative strategies.
162
It is the mating season for dung flies & there are two areas, each with dung piles with one female per dung piles producing eggs at a similar rate.
Area A: Average distance between dung piles is 10m.
Area B: Average distance between dung piles is 50m.
In which dung area would a male dung fly spend the more time? Draw graph & justify answer with it. (3)
• Male dung fly would spend more time in Area B.
• Graph: has one curve with 2 distances due to SIMILAR RATE.
• More time in B can also be concluded from distances between dung piles given.
163
MVT use?
To predict how much time an animal foraging for itself (as opposed to carrying loads) will spend in each patch/site before moving on.
164
Diminishing returns in each patch AKA?
Resource depression.
165
Pros of optimality models? (3)
● Allows you to test whether hypotheses that are presented in the model are right or wrong.
● Assumptions are made explicit.
● Emphasize the generality of simple decisions facing animals.
