Summary behavioural ecology

Project: 40%

Presentation: pass/fail

Exam: 60%



L1: hypotheses testing & economic decisions
p1-60



Behavioural ecology => study of evolutionary basis for animal behaviour due to
ecological pressures



Natural selection  adaptation & fitness

 Nat selection favours individuals who adopt life-history strategies that
maximise their gene contribution to future generations
- Behaviour of advantage to individuals may be disadvantageous to
group
 Behaviour  fit in environment  resources, survival & reproduction
- Competitive advantage over others  gene transfer
- Behaviour can be heritable or plastic
- Behaviour depends on ecological conditions



Natural selection theory Darwin

 Individuals within species differ in morphology, physiology & behaviour
(variation)
 Some variation heritable
 Competition between individuals for scarce resources
 Competition  some variants more offspring
- Offspring inherits characteristics: natural selection  adaptation
 Environment changes  evolutionary change



Natural selection: modern genetic terms

 Selection  changes in gene freq



When variants do better when they are rare  maintain behavioural
polymorphism



Most common clutch size often a bit lower than optimum

,  Increase lifetime breeding success
 Costs of egg production & incubation
 Trade offs



Behavioural trade offs: hypothesis testing

 Behaviour involves decision making: costs & benefits
- Trade off between c & b  variation
 Choice of how many eggs to lay  highly variable
- Current vs future reproduction
- Reproduction vs survival
- Costs: adult mortality
- Benefits: #surviving young
 Trade offs can be based on many traits & effects
 Marginal value theorem => balancing costs vs benefits
- Optimal decisions depend on c & b



Phenotypic plasticity => 1 genotype can alter its phenotype in response to
environmental conditions

 Continuous P variation  relationship between P & E for each G = reaction
norm
 Genetic change OR P plasticity



Economic decision making

 Economic analysis of costs & benefits  understand behaviour
 Diminishing returns => investment in patch increases  profit from patch
cannot continue to increase
- Resource depression
 Optimality theory
- Trade off between cost & benefit will give max net benefit
- Optimality model: assumptions about currencies & constraints
- Appropriate currencies can differ per case (e.g. efficiency or rate)
- E.g. optimal load size, optimal prey choice



Ultimate vs proximate

 Stages of scientific approach to understand function of behaviour:
1. Observations
2. Hypotheses (questions)
3. Predictions
4. Tests
 Niko Tinbergen: 4 questions (exam)
- Proximate: mechanism

, 1. Causation/mechanism: what is the trigger?
2. Development/ontogeny: what is the genetic & developmental
mechanism?
- Ultimate: adaptation
3. Function: what is adaptive advantage?
4. Evolutionary history: how did the trait evolve?
 Theoretical models useful to make hypotheses & predictions
 Tests
- Correlation ≠ causation  need experiments
- Systematically vary variable of interest
- Variable must be manipulated by experimenter (do not let animal
choose)
- Test against control group
- Random assignment of individuals to conditions
- Avoid confounding vars
- Suitable sample size
 Hypothesis testing
- Natural exp: compare individuals within species
- Manipulation experiment (costs & benefits)
- Comparative: compare between species



Comparative studies: limitations & solutions

 Data non independent: use phylogeny
 Cause-effect difficult (it is still a correlation): infer transitions
 Allows making broad inferences & predictions about adaptation &
evolutionary change




L2: mating systems
p254-281



Optimal mating system: varies between & within species



Mating systems

 Huge variation
 Understanding systems
- Individual aims to maximise reproductive success
 Types of systems
- Monogamy: 1 male + 1 female  often bi-parental care, animals can
cheat
- Polygyny: 1 male + multiple f  often only maternal care