L07 Behavioural variation, personalities & polymorphisms

example: night owls & early birds

study on how night owls have less support from friends & family

personality

repeatable & consistent behavioural variation between individuals

they influence the functioning of populations, societies, ecosystems

causes of personality

• behaviours are responses to conditions and conditions vary

• some behaviours are learnt and individuals learn diff things

• behaviours have genetic components, and genes likewise vary across individuals

advantages of personalities

• distinct benefits to distinct personalities

• diff behaviours trade off and it is necessary to specialise

pros of behavioural consistency

• social aspects, better everyone do same thing (e.g. ants turning left)

• sometimes one optimum behaviour for everyone (e.g. run from a fire)

• simpler to encode genetically & to govern mechanistically

cons of behavioural consistency

• everyone’s predictable (to predators)

• novelty and innovation rare

• completely expunging variation may be impossible

5 commonly recognised aspects of human personality

• openness

• consciousness

• extraversion

• agreeableness

• neuroticism

pseudoscientific behavioural economics

unreliable (not getting the same)

says things that appeal to everyone

anthropomorphism

considering animals as if they have the same cognitive experience of the world as we do

relevance of anthropomorphism in ethology

• it stopped scientists from seriously considering personality as a topic

• individual differences = just noise, dismissive

• expected only one optimal solution to set situation

• personality in animals studied in 90s

• IMPORTANCE of anthropomorphising: humans and animals similar, same level

animal personality main traits, 5

shyness/boldness → (e.g. predator) risk taking

exploration/avoidance —> new habitat

activity level —> this changes exploration/bold/shy, so activity measured in NON-risky or NON-novel envmt

aggressiveness —> agonistic reaction tw conspecifics

sociability —> reaction to presence or absence of conspecifics, seeking or avoiding conspecifics

shyness/boldness case thingy

bold - sensation seekers

shy - inhibited behaviour

context specific

e.g. Pumpkinseed fish, cage vs seine nets (catch bold vs catch all fish)

• bolder fish => less scared of human observers

• shy fish => more parasites, foraging in diff habitat

BUT lost personality once lab envmt ==> need social/ecological cues for personality

exploration/avoidance in great t*ts

given demonstrator

explorers: did not follow demonstrator to different feeders but learned alone

non explorers: followed demonstrator

multiple aspects of behaviour were combined to make exploration

SNP830

curiosity gene

birds , exploration/avoidance

What is behavioural repeatability?

Proportion of behavioural variation attributable to differences between individuals

What does high behavioural repeatability indicate?

Individuals consistently differ in their behaviour.

What statistical measure is used to quantify repeatability?

Intraclass correlation coefficient (ICC)

aggression in bluebirds

• western bluebirds —> mountain bluebirds

• early western colonisers = highly aggressive

• those aggressive = poor parents

• non aggressive = better parents => did better

= CIRCUMSTANCES ALTER THE BENEFIT OF EACH PERSONALITY TYPE

fluctuating selection

when either strategy may be best, depending on circumstances

explains the persistence of more than one personality type

What does behavioural repeatability tell us about animal personalities?

Whether individuals maintain consistent behavioural differences across repeated observations., cf. slide 29

behavioural plasticity

Individuals can change how they behave depending on their circumstances or environment.

For example:

• On a warm day, you remove some clothes.

• Similarly, an animal might become less bold after a negative experience.

plasticity vs consistency

• Consistency: individuals maintain their relative behavioural differences.

• Plasticity: individuals can adjust their behaviour in response to changing circumstances.

For example, a naturally bold fish might become less bold after losing a fight, but still remain bolder than a naturally shy fish

example flexible personalities

rainbow trout, classified as bold or shy

demonstrators

==> possibly adaptive plasticity

• bold fish given negative xp reduce boldness

• shy fish ++boldness after positive xp of boldness ——-to novel object

polymorphism

trait that is commonly observed in multiple discrete forms in a given. animal population

e.g. hair color

PB: why?

game theory : how 2 strategies can be maintained

Hawk: always fights. Dove: displays aggression but retreats from physical fights.

What is an Evolutionarily Stable Strategy (ESS)?

A strategy or population mixture that cannot be successfully invaded by an alternative strategy.

why pure dove or pure hawk not a ESS

Hawks can invade, win all encounters and take resources.

High injury costs allow Doves to persist without fighting.

relative fitness & freq in population of Hawk-Dove

Their relative fitness depends on their frequency in the population. => coexistence.

intersection of Hawk and Dove fitness lines represents a stable population mixture where both strategies have equal fitness.

if either strat too common:

Its fitness decreases relative to the alternative strategy, pushing the population towards equilibrium.

bourgeois strategy

speckled wood butterflies on territory ownership

playing hawk when owning a territory and dove when invading

antibourgeois strategy

mexican spiders in gaps of stone walls

territory holder plays dove and attacker plays hawk

domino dynamic constant displacement

bc lots of territory and fighting is expensive = adaptive strategy

wars of attrition

competition is not 2 choices but how long to hold out

how long should individual stay depends on resource & how long rivals stay

side blotched lizards

3 morphs; orange, yellow, blue

orange => usurpers (aggro sluts)

yellow => sneakers (cheats behind usurpers)

blue => mate guarders (spot sneakers, lose fights w usurpers)

ROCK PAPER SCISSORS

orange kills blue kills yellow kills orange

2 feeding behavior, pigeons

Producers open food tubes; scroungers eat food released by producers.

Research: 16 : 2 prods-16scroungers

NOT cultural transmission, scroungers could not learn

=> diff feeding strategies can coexist

large cactus finch

males w song A => short bills

males w song B => long bills

B males punch holes in cactus fruit and eat fleshy pulp

A males tear apart cactus base and eat flesh and insect larvae

territories of A & B random but mated males alternate

BC living next to someone eating diff is best for your food availability

2 outcomes of behavioural variation

speciation

heterogeneity and disease spread

outcome 1: speciation, e.g. darwin’s

Darwin’s finches in Galapagos => diff beaks eat diff foods

diff beaks = diff song repertoires

diff => difficulty to mate w conspecifics w diff songs

===> speciation

conspecifics

from same species, peers

outcome 2: heterogeneity and disease spread

BC differing in bh —> diff contact rates per individuals

superspreaders: individuals w lots of contacts => likely responsible for majority of transmission events

EVEN complex beh….

HAVE A GENETIC COMPONENT

• fx of additive genetics, individual identity, year and residual variation.

• The point: even quite complex behaviours, such as mule-deer migration, can have a genetic component.

defaunation & habitat fragmentation

The loss of animal species from an ecosystem; it can be associated with reduced diversity of personality traits in remaining populations.

Habitat fragmentation = habitats become divided into smaller, isolated areas.

individual specialisation

Generalist populations are often comprised of specialist individuals.

Meaning:

• A species/population may collectively use several different food sources.

• But individual animals may specialise in particular food sources.

• So the population looks generalist, even though its members behave differently.

why look at multiple traits

Individual differences may become clearer when several behaviours are considered together, even if individual traits have low repeatability.

overall behavioural variation significance

It affects individual survival and reproduction, population dynamics, ecological interactions and even speciation and disease transmission