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BS2077 - Neuro & Animal Behaviour > Barber > Flashcards

Barber Flashcards

1
Q

What does behavioural ecology focus on

A

Behavioural Ecology focuses on the function of behaviour, its adaptive nature, and its evolution under ecological constraints:

  • ‘The study of the survival value of behaviour’
  • ‘How behaviour contributes to reproductive success’
  • ‘The study of how an organism’s behaviour affects its chances of passing on genes to the next generation’
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2
Q

Describe Crook’s weaver birds

A
  • Ploceidae
  • Speciose group of sparrow-like passerines; Africa & Asia
  • Different species inhabit very diverse habitats (cover, food type, predation threat)
  • Parallel variation in species-specific patterns of behaviour (inc. nesting dispersion, feeding behaviour, mating systems)
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3
Q

Describe Crook’s comparative approach

A
  • Attempt to relate observed species variation in behaviour patterns to ecology, and then map this to phylogeny
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4
Q

Describes MacArthur’s costs and benefits model

A
  • Costs may be energetic or ‘lost opportunity’
  • Benefits may be direct or indirect
  • Trade-offs needed to balance costs and benefits
  • Natural selection favours animals that make economically-valid ‘decisions’
  • ‘Optimality models’ of behaviour can be generated
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5
Q

Describe the three components of MacArthur’s models

A
  • Assumptions about what choices are available
  • Assumptions about what is being maximised
  • Assumptions about constraints
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6
Q

Basically describe altruism and eg.

A
  • Behaviour that increases the survival of others whilst decreasing the survival of the altruist
  • Observed in natural animals populations; co-operative breeding (scrub jays), collective offspring care (lions)
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7
Q

Hamilton’s altruism and relatedness

A
  • Parents-offspring share 50% of their genes
  • Brothers/sisters share 50% of genes
  • Grandchildren / grandparents share 25% of genes
  • Cousins share 12% of genes
  • Inclusive fitness is the success of all genes you share with others being transmitted to future generations
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8
Q

Describe Tinbergen’s gulls

A
  • Eggshell removal - black-headed gulls
  • Tinbergen painted hens’eggs to resemble gulls eggs
  • Placed them in the gull colony, some next to broken shells
  • Eggs next to broken shells were more likely to be discovered and eaten
  • Removal of empty shells therefore appears to be an adaptive response to the presence of predators
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9
Q

Describe serengeti lions

A
  • Panthera leo
  • Live in prides
    3-12 adult females (related)
    1-6 adult males
    Several cubs
  • Females born in pride remain there and reproduce from age 4-18
  • Male offspring leave pride when 3 years old and become nomadic before attempting to over a pride
  • Males only remain in a pride for 2-3 years until driven out by others
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10
Q

Observation 1: All females in a pride enter oestrus at the same time – WHY?

A

Causal explanations:
- Chemical / pheromone cues synchronise oestrus cycles

Functional explanations:

  • Cubs born synchronously survive better
  • Synchronous and communal suckling
  • Greater chance of male cubs having a related, same age companion to leave pride with
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11
Q

Observation 2: Despite phenomenal rate of copulation, birth rate is low – WHY?

A

Causal explanations

  • Female infertility?
  • Concealed time of ovulation

Functional explanations

  • Advantageous to females to be receptive at times when conception is unlikely
  • 1:3000 chance that a copulation will result in a birth
  • Increases paternity uncertainty amongst males
  • Reduces competition between males
  • Incites sperm competition, possibly increasing the chance of a high quality male being the father
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12
Q

Observation 3: All young die when new males take over – WHY?

A

Causal explanations

  • Aggressive males kill cubs
  • Hormonal changes in females resulting from the takeover causes abortion of unborn young

Functional explanations

  • Females come into oestrus quicker when not nursing cubs
  • Males remove non-related offspring, which would compete with their offspring
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13
Q

Describe the way genes attribute to behaviour

A
  • Natural selection acts at the level of the individual
    (Beware ‘group selectionist’ ideas and arguments!)
  • But individuals only act as temporary vehicles for genes…
  • Individuals therefore typically act selfishly
    ~ To maximise their lifetime reproductive fitness
  • There is a genetic component to behaviour
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14
Q

Give an overview of an example of empirical evidence of selfishness

A
  • Great tits (Parus major) Wytham Woods, Oxford
  • Long-term (40-year+) study
  • Most pairs lay 8-9 eggs
  • Egg addition experiments show that more can be successfully incubated and hatched
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15
Q

Why do great tits not lay more eggs

A
  • Mean fledgling weight decreases with increasing clutch size
  • So parents cannot support larger clutches in most years
  • Food availability and parental effort is limited
  • Heavier fledglings have a greater chance of survival
    40% of fledglings >20g are recovered after 3 months cf only 5% of
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16
Q

Why was the optimal clutch size larger than thought

A
  • Experimental manipulation of clutch sizes performed
  • Clutch sizes that maximised the success of offspring peaked at 8-12
  • Expected optimal clutch size was larger than observed
  • Visser & Lessels (2001) experimentally manipulated clutch size in different ways
  • ‘Free eggs’ and ‘free chicks’ increased female fitness
  • But when they had to pay ‘full costs’ of incubation, then fitness was reduced for ‘enhanced clutch’ females
  • Restriction of clutch size is therefore optimal and selfish
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17
Q

What are the three types of evidence for genes

A
  • Genetic mutants
  • Artificial selection experiments
  • Population level genetic differences
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18
Q

Describe the genetic mutant experiements

A

Benzer (1973) used radiation and chemicals to produce reproductive mutations in Drosophila fruit flies:

  • normal copulation takes 20min
  • ♂ ‘stuck’ mutant phenotype failed to disengage after copulating with females
  • ♂ ‘coitus interruptus’ mutants disengaged after only 10mins

Learning mutants have also been isolated:

  • ‘Dunce’ mutants do not learn to avoid odours associated with a subsequent electric shock
  • ‘Dunce’ phenotyope caused by abnormality in the gene for cyclic AMP phosphodiesterase, which breaks down the intracellular messenger cyclic AMP
  • ‘Rutabaga’ mutants also do not learn
  • ‘Rutabaga’ phenotype caused by abnormality in the gene for adenyl cyclase, which converts ATP to cyclic AMP
  • All learning mutants have perturbed secondary cellular messaging systems (also called ‘learning pathways’)
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19
Q

Describe artificial selection experiments

A

Manning (1961) artificially selected for two different mating speeds in fruit flies by performing controlled crosses:
- ‘Slow’ and ‘fast’ males identified in one generation and bred with females in separate colonies
- Slowest and fastest males then selected from each new generation
- Mating speed diverged even further over generation time
Likely additive genetic effects

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20
Q

Describe studies of populations with genetic differences

A

Geographically distinct populations of a single species often differ in morphology and behaviour

  • These differences often reflect differing ecological conditions
  • Prey preferences of garter snakes (Arnold, 1981) slugs

Blackcaps
(Sylvia atricapilla)
- Populations vary in their degree of migration
- All German birds migrate
- British blackcaps are partial migrants; some migrate, others over-winter
- All Cape Verde Islands birds are non-migratory

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21
Q

Describe evidence for the genetic basis of behaviour

A
  • Berthold (1990) crossed migratory (German) x Non-migratory (Cape Verde) birds
  • Crosses gave 40/60 migratory/non-migratory offspring
  • Direction of migration of F1s was like German parents
  • Suggests >1 gene is involved
  • Selective breeding from one partial migrant population also allowed migratory and non-migratory strains to be recovered
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22
Q

Describe genetic determinism

A

Not necessarily one gene per behaviour

  • Behaviours are complex, multigenic traits
  • But differences in behaviour may be due to differences in one gene, since genes code for enzymes which affect development

Genes do not determine behaviour alone

  • Nature vs. nurture debate!
  • Environmental effects are important
  • The development of behaviour is a result of complex interactions between genes and environment
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23
Q

Describe genes as units of selection

A
  • Richard Dawkins, Oxford University.
  • Genes create phenotypes, which are then selected on by natural selection
  • The most successful genes will be those that maximise survival and reproductive success
  • Therefore we expect individuals to behave so as to promote gene survival
  • ‘Because of the way natural selection works, it is reasonable for us to picture an animal as a machine designed to preserve and propagate the genes which ride inside it…’ (Dawkins and Krebs, 1978)
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24
Q

Modern explanation of Darwin’s theory (7)

A

1) Organisms have genes which code for protein synthesis
2) These proteins regulate the development of the nervous system, muscles and structure of an organism and therefore influence behaviour
3) Many genes exist in two or more forms (alleles) which code for slightly different forms of the same protein
4) Different alleles confer slight differences in development and behaviour, generating variation in a population
5) There is competition on the chromosome between alleles of a gene for space (at a locus)
6) Any allele making more surviving copies of itself will eventually replace the alternative form in the population
7) Natural selection is the differential survival of alternative alleles

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25
Q

SUMMARY 1

A

Behavioural Ecology is the study of the function of behaviour

BE can be defined as ‘The study of how an organism’s behaviour affects its chances of passing on genes to the next generation’

BE was formed as a result of the convergence of ideas from field ecology, ethology, mathematical ecology, theoretical biology and evolutionary biology

Aspects of the behaviour of Lions in the Serengeti can be explained in both causal and functional terms

BE has an extensive, readily-accessible literature

Studies on the clutch size of great tits identified that individuals appear to act selfishly to maximise their own chances of producing ‘fit’ offspring

We examined the evidence for a genetic basis of behaviour, and the problems of ‘genetic determinism’

We then considered whether individuals or genes are the units of selection

We examined the Dawkins view of selfish genes

We examined how Darwin’s theory of Evolution by Natural Selection can be ‘modernised’ and made relevant to behaviour

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26
Q

Briefly describe optimality modelling in BE

A
  • Natural selection is iterative and competitive, producing behavioural phenotypes that represent the best achievable balance of costs and benefits
  • Individuals exhibiting sub-optimal cost-benefit balances (trade-offs) will leave fewer offspring
  • Hence, individuals are expected to evolve to behave optimally (within the bounds of ontogenetic constraints)
  • Based on cost:benefit analysis
  • Makes quantitative predictions about behaviour
  • Seeks to identify what trade-off between costs and benefits of a behaviour will maximise net fitness
  • Use models to generate testable hypotheses
27
Q

Optimality modelling key concepts

A
  • All behaviour takes time
    which cannot then be allocated to other activities
  • All behaviour costs energy
    which cannot then be allocated to other activities
  • If animals do try to carry out two types of behaviour at once, efficiency in both is typically lost
    foraging / keeping watch for predators
    multitasking in humans
  • The benefits of any behaviour are context dependent
  • Temporal variation (daily, tidal, oestral, seasonal or developmental)
28
Q

Describe welk-dropping by corvids

A
  • Crows in coastal areas feed on shellfish
  • Whelks (Nucella) dropped onto rocks from height
  • Take-off and vertical flight is very costly for birds
  • Observed dropping height supports the hypothesis that crows open whelks using the minimum energy possible
29
Q

What are the two approaches to modelling?

A

Verbal models

  • Advantages: easily understood
  • Disadvantages: ‘woolly’,

Formal mathematical models

  • Advantages: explicit; clarify exactly what is assumed and what is predicted
  • Disadvantages: requires some effort!
30
Q

Describe the optimal foraging methods

A
  • The functional approach:
    Comparing actions in terms of their contribution to future reproductive success (FRS, the ‘ultimate currency’)
  • But difficult to assess FRS
    Instead focus on simpler ‘currencies’
  • Net rate of energetic gain (, gamma)
  • Foraging efficiency (E/h, energy/handling time)
    -Others (starvation / predation avoidance, nutrient limitation)
31
Q

Describe net rate of energetic gain method

A

Maximising gamma means:

  • maximising the amount of energy gained per unit time spent foraging
  • minimising the time required to obtain a given amount of energy

gamma=b-e
gamma is net gain rate
b is energetic gain rate
e is energetic loss rate

32
Q

How can net rate of energetic gain be applied to kestrel foraging

A 
Kestrels spot prey either by flight (f) hunting or perch (p) hunting
In winter (values differ in summer):
bf  = 132 kJ/hr
bp = 13 kJ/hr
ef  = 52 kJ/hr
ep  = 7 kJ/hr
  • Flight gammaf = 132 - 52 = 80kJ/hr
  • Perching gammap = 13 - 7 = 6 kJ/hr
  • In winter, flight hunting is by far the more common form of hunting
  • BUT perch-hunting still occurs…
  • Example shows how rate-maximising models can be used, but also that other currencies may be more relevant
33
Q

Describe Mars bar model

A
  • Mars bars come in a variety of sizes
  • Cost (pence) per kJ of energy can be calculated
    giving us one currency (‘value for money’, in kJ.pence)
  • Preferred bar size should be Kingsize, assuming ‘value for money’ is the currency being maximised
  • BUT what about other constraints / currencies?
    Handling time, cost, appetite, gape limitation
  • Larger food items contain more energ but they also take longer to catch and eat
  • E/h = energy gained / handling time
34
Q

Describe prey selection in redshanks

A
  • Redshanks feed on mudflats on the polychaete Nereis
  • A range of Nereis sizes are available
  • Sometimes birds feed only on large worms, sometimes they take both large and small worms
  • Goss-Custard (1977) suggested that small worms were rejected when large worms were common, but taken when large worms were rare
  • By manipulating the encounter rate with large and small worms, and by knowing their relative e/h profitability, Goss-Custard was able to predict the point at which redshanks started taking small worms
35
Q

Give a model of choice between large and small prey

A
  • Two prey types: large prey1 and small prey2
  • Large prey have energy value E1, and handling time h1
  • Small prey have energy value E2, and handling time h2
  • Profitability of large prey is E1/h1
  • Profitability of small prey is E2/h2
  • Imagine that large prey are more profitable:
    E1/h1 > E2/h2
36
Q

Factor in search time for a small vs large prey choice

A
  • Assume a (hungry) predator has encountered a prey item. Should it eat it or not?
  • If prey is large, it should always eat it
  • Therefore the decision to eat large prey doesn’t depend on the abundance of small prey
  • What if the prey is small?
  • Small prey should be eaten provided that:
  • Gain from eating exceeds the gain from rejection and searching for a more profitable prey item:

E2/h2 > E1
S1 + h1

Where S1 is search time

37
Q

When should a preditor include smaller, less profitable prey items into its diet?

A

S1 > (E1 h2/E2) - h1

Thus, including less profitable items in the diet will depend on the abundance of the more profitable prey

38
Q

When can we work out when animals specialise solely on more profitable prey type

A

If we know:

  • the energy content of the two types of prey items
  • their associated handling times and
  • the time taken to search for the more profitable prey
39
Q

What predictions can be drawn from the small vs large prey model?

A

1) The predator should either:
- Specialise solely on prey type 1 (more profitable prey) OR
- Eat both prey type 1 and prey type 2 (less profitable prey) as the are encountered
- (should not specialise on prey type 2)

2) The decision to specialise on type 1 prey depends on S1, not on S2

3) The switch from specialising solely on prey type 1 to generalising (eating both prey sizes as encountered) should be sudden, as the commonness of the best prey decreases
- i.e. there should be no partial preferences

40
Q

How was the prey choice model tested with great tits Parus major

A
  • Great tits offered large and small mealworms on a conveyor belt system to control encounter rates
  • Large mealworms contained ~ twice the energy than small ones (E1/E2 = 2)
  • Encounter rate with large worms was changed throughout the experiment to span the predicted switch-point
  • Predicted that there would be a switch when there was no +ve or -ve extra payoff for large but actually observes % specialisation was less and showed partial preferences as extra payoff increased
41
Q

Describe Marginal Value Theorem (MVT) with 2 eg

A
  • Model used to understand a variety of topics in BE
  • Useful tool to determine how long individuals should persevere when experiencing diminishing returns for their efforts with increased time
  • e.g.1 Starlings loading up with leatherjackets (Tipula larvae)
  • e.g. 2 Dungflies guarding mates following copulations
42
Q

Describe Marginal Value Theorem in relation with starlings

A
  • Birds provisioning chicks are limited by the amount of food they can carry in their beaks
  • The rate at which they can fill up their beaks decreases as the beak fills up
  • Costs and benefits of small and large load sizes
  • Assume that starlings are efficient parents
  • ‘Diminishing returns’ curve where gain levels off as beak load and search time increases
43
Q

What is the effect of patch density on MVT curve?

A
  • Higher the density, quicker the rate of the curve, so will increase faster, have a higher max and level off sooner
44
Q

MVT starling study SUMMARY

A
  • Starlings become less efficient at adding one more prey item to the load as load size increases
  • Loading rate therefore constantly decreases during one foraging bout
  • Expecting starlings to be efficient parents, we predicted that they should maximise rate of prey transfer to offspring over time
  • The number of prey taken in a single bout should depend on travel time and patch quality
  • Experimental tests strongly supported predictions from the model
  • As round trip time increased so did mean load size
45
Q

Describe MVT and reproductive decisions in dungflies

A
  • Males compete for females on fresh cowpats
  • Males can physically dislodge competitors as they attempt to mate
  • When >1 male mates with one female, last male fertilises about 80% of the eggs (but depends on time spent copulating)
  • Males therefore try to stay ‘attached’ to females after insemination
46
Q

What are the types of ‘currencies’

A

So far looked at a number of currencies:

  • Minimising energy expenditure (Crows / Whelks)
  • Maximising net energetic gain (Kestrels)
  • Maximising ‘value for money’ (Mars Bars)
  • Maximising rate of food transfer to chicks (Starlings)
  • Maximising number of offspring sired (Dungflies)

Other, less obvious, currencies may be important:

  • Minimising risk of starvation (Juncos)
  • Limiting nutrients (Moose)
  • Avoiding predators (Sticklebacks / Zebra finches)
47
Q

Name the types of competition

A

Interference
- ‘Reduction in an individual’s rate of prey intake as a result of competition’
- Simple exploitation: resources removed by other competitors (which do not even need to meet each other)
- Scramble: competitors see each other using the same resource; interference over each resource item; fastest responder wins; no aggression
- Contest: competitors interact aggressively over resource items; winner (‘despot’) may be able to exclude access by others; can lead to…
Resource defence
- ‘economically defendable resources’

48
Q

Describe the importance of spatial distribution of resources

A
  • Interference competition more likely when resources are aggregated
  • Also increased chance with increasing density of competitors
  • Competitors forced into closer contact
  • Increased chance that >1 competitor deciding simultaneously to ‘go for’ one prey item
  • Also increases chance that:
    aggression may occur
    resources may become economically defendable
49
Q

Give an example of the importance of spatial distribution of resources

A
  • Brown hares (Lepus europaeus)
  • Normally solitary/pairs, but will form feeding aggregations to give improved vigilance
  • Fed apple pieces, either:
    in a single clump
    spaced at 1m intervals
  • Amount of aggression recorded (one hare displacing another from a food item)
    Low levels with dispersed food
    Much increased with clumped food, and increasing with group size
50
Q

Describe the importance of the temporal distribution of resources

A
  • How do resources appear in time?
  • ‘Clumped’ or ‘spaced’
  • Renewable resources: appear ‘sequentially’
  • Competitors forced to interfere over each resource item
  • cf. situation if all food introduced together (‘clumped’)
  • Feeding fish in pond, sparrows in park etc…
  • Temporal clumping of resources reduces competition, whereas spatial clumping of prey increases competition
51
Q

Describe ideal free distribution (IFD)

A
  • Fretwell and Lucas (1970)
  • Model to describe the distribution of competitors in a patchy environment
  • ‘Free’ – all animals are free to move around without constraint or restriction
  • ‘Ideal’ – each animal has complete information regarding the availability of resources, allowing movement to a location where it will maximise its returns
  • Number of competitors in each patch balances so that no individual can better its return by moving to another patch
52
Q

Give a human example of Ideal Free Distribution

A
  • Supermarket checkout queues
  • Queue joined depends on length of queue and efficiency of assistant…
  • Requires knowledge about each variable
53
Q

What are the principles behind Ideal free Distribution (IFD)

A
  • Reward per individual diminishes as number of competitors increases
  • Rich habitats fill up quickly, so payoff decreases
  • May become viable to move to less rich, but less exploited habitats
54
Q

Describe Ideal Free Distribution mathematically

A
  • N equal competitors
  • Resource items arrive at different patches at different rates - In a given time period, Q1 items arrive in patch 1, Q2 items arrive in patch 2, Q3 items in patch 3 etc
  • We want to predict the number of competitors that should use each patch
    n1 in patch 1, n2 in patch 2, n3 in patch 3 etc
    n1+n2+n3 = N
  • Define the number of items gained per competitor (Gi)
  • In IFD, all Gi’s are equal: G1 = G2 = G3 = …Gi = Constant (C)
  • Gi will depend on the number of competitors (ni) and the input rate to the patch (Qi):
                       Gi = Qi / ni
55
Q

IDF for equal competitors

A
  • Because Gi is constant in all patches -> ni=Qi/C
  • So, number of competitors in a patch should be directly proportional to the input rate
  • This is the ‘Input Matching Rule’
  • IFD for equal competitors is the simplest IFD model
56
Q

Describe IFD in sticklebacks

A
  • 6 fish in an aquarium
    Prey (Daphnia) pipetted into ends at different rates
  • One end 2x rate of other
  • ‘Continuous input’ – resources not depleted
  • Fish distributed themselves 4/2 at rich/poor ends of the tank
  • Swapping rates led to a re-distribution of 2/4
  • Fish could not better their food intake by moving to the other patch
57
Q

Is continuous input model realistic?

A
  • In some cases:
  • Drift foraging in stream-living fishes
  • Algal grazing catfish (Power, 1984)
  • Algae grew 6x quicker in sunny pools than those in the shade
  • Catfish were 6x more abundant in sunny pools than shaded ones
  • But mostly, resources become depleted over time
  • Complicates IFD predictions
58
Q

What other assumptions are made for the simplest IFD model?

A
  • Resources are all equally valuable (no size / quality variation) - unrealistic
  • Competitors are equal - untrue!
59
Q

Describe IFD for unequal competitors

A

Imagine a simple system:

  • population has just two competitive phenotypes
  • A [good] and B [poor]
  • A has a ‘competitive weight’ of 2, B has a ‘competitive weight’ of 1
    i. e. A gets twice as much food from a patch than B
  • If there are 2 A phenotypes and 4 B phenotypes in patch, total ‘competitive weight’ is 8
  • If each competitor’s share of the input to be proportional to its competitive weight:
  • A phenotype individuals should gain 2/8, and
  • B phenotype individuals should gain 1/8 per unit time
60
Q

How are unequal competitors in IFD equilibrium

A
  • A number of ways in which unequal competitors could distribute themselves to allow same rate of food intake
  • Alternative equilibrium distributions exist
61
Q

Test for IFD for unequal competitors

A
  • Gall aphids (Phylloxera)
  • Females (‘stem mothers’) settle on stems of leaves and begin reproducing
  • Stems of large leaves can support 7x the offspring production of those in small leaves
  • Large leaves occupied first; late settlers have a choice of:
    selecting a smaller leaf, or
    co-occupying a large leaf
  • For any competitor density, reproductive success increases with habitat quality (leaf size)
  • For any given leaf size, reproductive success decreases with increasing competitor density
  • Average reproductive success of aphids alone on a leaf, or sharing with one or two others, was not significantly different
  • Supports predictions of IFD
62
Q

Describe despotic distribution

A

When animals show aggressive guarding of resources; territories form in high quality habitat
As territories in high-quality habitat fills, no more competitors can enter (a)
Further competitors forced into low-quality habitat
When this fills up (b) further competitors become ‘floaters’ (non-territory holders)
Not ‘free’ to move around
Predictions of IFD may not apply

63
Q

Describe economic defendability of a resource

A
  • Despotic distributions only develop when resources can be monopolised
  • Resource defence confers benefits to the defender, by guaranteeing resources (food, mates, shelter etc)
  • Also costly – energy expenditure, risk of energy
  • Territorial behaviour should be favoured when costs are outweighed by the benefits of resource defence
  • Need to quantify the energetic costs and benefits of territory defence
64
Q

Describe defendable and non defendable resources

A
  • Brown hares (Lepus europaeus)
  • In clumped food treatments, as the number of group members increased:
  • dominant individuals spent more and more time chasing, and less time feeding
  • non-dominant individuals spent more time feeding

BS2077 - Neuro & Animal Behaviour (7 decks)

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