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BLGY3155

Lecture 1 - Introduction to behavioural ecology Behavioural:

Survival: find food, compete for food avoid predators

Reproduction: find mate, compete for one, mating behaviour Why does animal do particular behaviour?

explain the ultimate survival/reproductive value or function of the behaviour ultimate functional explanation- why has particular behaviour evolved

other biological factors- causation (what causes behaviour), development (do offspring learn from parents), evolutionary history (links with adaptive value)

Why does starling sing: Territory

Mates Warning cry

Lions in Serengeti live in prides:

Different selective expresses between male and female lions

Infanticide in humans Daly and Wilson 1994

Infanticide of offspring by genetic father Highest in young children (0-2)

5 million

Homocide by stepparent per million Much higher in younger children (0-2) 600 million

introduction to behavioural ecology book-4th edition

observation casual explanation functional explanations

females are synchronous in oestrus

chemical cues better cub survival

males do better in groups when leave pride

share in care for cubs females are all related

if related males are kicked out as group they survive bettie

high rate of copulation female infertility

time of ovulation concealed males keep mating with female

cubs survive better

increased paternity uncertainty may protect cubs from males

young die when new males take over pride- infanticide

abortion (chemical?) males kill/evict young

disadvantage to female- female has used resources

advantage for male- opportunity to produce his own offspring

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BLGY3155 Behavioural ecology: Behaviour Ecology Evolution Adaptation: Variation Heritability

Competition- limited amount of resources

Natural selection - favours one carrying better gene traits Adaptation as a result of natural selection

Genes influencing behaviour

1. Genetic mutants- irrigation-stuck marker

• Dropshila- when they mate they mate for 20 mins • Genetic manipulation- knock out gene for this behaviour • Behaviour gets selected out

2. Artificial selection • Fast vs slow mating • Manning- 1961

• Separate the ones that did longest and shortest mating

• Only mated one that did longest with longest and same for short ones • Artificial selection

• Separate the 2 groups even further in mating time 3. Between population differences

Heritable food preferences in garter snakes Foraging behaviour in fruit flies

Rovers- forR • Search for food

• For codes for enzyme that is produced in brain and affects behaviour

• Good short term memory- adaptive for fast learning as they move between food patches • Exploratory behaviour- seeking out best food resources

Sitters- forS

• Remain in 1 area to feed • Good long term memory

(Negative) frequency dependent selection:

Advantage is influenced by how much food your taking in Retain polymorphism

Allele is maintained

Success of rover or sitter is negatively frequency dependent

Population is dominated by sitters- individuals who are rovers will do well

Alleles of rover wills spread into the next generation until they dominate the population Loads of fruit flies looking of food

Some will still be sitters

Find food and eat in one place- start to do better than rovers Sitters allele starts to spread again- advantageous allele Success is dependent on what the other population is doing Frequency dependent fitness

Key concept

Fitness depends on adaptions to environment

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BLGY3155 AND on fitness relative to competitors

Fitness may be frequency dependent Behaviour and natural selection ?? to ensure survival of the species?? BUT selection acts on individuals

GROUP SELECTION (Wynne Edwards 1962) Lion infanticide

Not good for species or the group Selfish individuals

Talking about adaptive behaviour

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BLGY3155 studies:

Adaptations of female lions to infanticide by incoming males Packer and Pusey (1982)

Introduction:

Infanticide- males kill infants of unfamiliar females advantageous to infanticidal male

disadvantage to females

mechanisms where some females animals reduce losses to infanticide: behaviour of females that prevents males from killing their young:

females succeed in aggressively defending their young against unfamiliar males avoid new males by leaving the group

pregnant females show psuedoestrus and mate with new male- confuses paternity ensuring survival of infant females minimises losses when death of offspring is inevitable:

‘bruce effect’- pregnancy is terminated by exposure to new males or their scent minimise time and energy invested in offspring

female lions show a period of infertility and heightened sexual activity in male takeovers to reduce frequency of offspring loss

Method:

record incidence of wounds and reproductive condition and sexual activity of females results and discussion:


immediate resposnses: defence of cubs:

mother vigarusly attacked infanticidal male (mothers wounded) cooperative defence- communal rearing of cubs

avoidance of new males:

mothers accompany older cubs (1.5-2yo) to new area (nomads) cubs (6-17mo)- remain in pride- avoid alien males

pseudo-estrus:


female lions show estrus behaviour and mate during pregnancy estrus during pregnancy is rare- only saw 2 cases of this spontaneous abortion:


pregnant females abort at takeover

impossible to determine is newly pregnant females abort at takeovers effects on female reproduction and reproductive activity:

reduced fertility:

resume sexual activity, regular estrus cycles- fertility is lower

fertility is lower when cubs are lost at takeover than loss of cubs under other circumstances lactating females that lost cubs at takeover gave birth with new male 110 days later than females that lost cubs and mated with same male who fathered their previous litter

females that lost cubs at takeover take 6-9 oestrus cycles to become pregnant

females that lost cub under other circumstances take 1-2 oestrus cycles to become pregnant bertram (1975)

no pregnancies were initiated until after 3.5mo females were infertile for 102 days after takeover they are reacting to newness of males

females become more familiar and more likely to become pregnant- females investigate male markings

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Lecture 2- Mate choice and sexual dimorphism

Dimorphism

Di- two

Morph- form/shape Examples

Stag beetles Odontolabis femoralis

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Elongated mandibles

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Fighting displaying using mandibles

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Allows access to females when in competition with other males Peacocks

Genders differ in morphology and behaviour

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Females- drab in colour

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Males- long colourful tail with eye spots Males display tail to attract mates

Tail doesn’t help with flight Mallard

Female- dull in colour Male- colourful

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Not camouflaged

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Reduction in survival potential

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Invested a lot in glossy plumages

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Lots of carotenoids and other chemicals

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Costly to maintain

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To maintain needs to be in good health Chickens

Demonstrate different displays Males:

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Shiny glossy plumage and tail

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Spurs on back of feet- cock fighting –access to females

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Cone- erectile tissues

Sexual selection

Why do the sexes differ?

Why is the male usually the more elaborate sex?

Primary sexual characteristics- essential for reproduction e.g. ovary and testes Secondary sexual characteristics- not essentials for mechanics, strongly selected for

Why such risky male displays?

Why invest in costly behaviours that attracts mates and predators Fundamental different selective pressures on males and females Why it leads to differences in behaviours?

Tungara frog

Display orally- deep croak- shows how attractive male is Bigger male = bigger chest = bigger voice box = deeper croak Risk of predation by bats due to them being attracted by the sound

Selection

NATURAL SELECTION:

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individual selected according to its ability to survive and reproduce SEXUAL SELECTION:

individual selected solely by its ability to obtain mates male/male competition

attractiveness to the opposite sex

Sexual selection depends on the advantage which certain individuals have over others of the same sex solely in respect of reproduction.

Why are females choosey?

Individuals of the sex which invests more in gametes will be choosey (females) • Selective push for females to be choosy

Individuals of the sex which invests little in gamete will compete for access to the high investing sex (males) • Selective push for males to mate as many females as possible

High investing sex- gametes are in short supply

Gamete size

Egg- large and only 1 released at a time Sperm- small and in large supply Female reproductive success:

• Limited by her ability to produce and resource the gametes • To resource eggs females use a lot of energy

Male reproductive success:

• Not constrained by number of sperm produced • Males restricted by access to rare female gametes Anisogamy

An- not Iso- the same gamy-gametes

Not the same sized gametes

Drosophila melanogaster reproductive success. Bateman 1948 Offer mating opportunities in experiment

How many offspring produced?

Mean number of offspring produced Number of mates Female Male

1 70 50

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Getting mated isn’t the thing that affects females ability to produce offspring

Her ability isn’t limited by sperm but producing and resourcing her own gametes Selection will favour male who mates with multiple females

Female only needs to mate with 1 male to ensure fertilisation

Demonstrates why males develop elaborate behaviours to attract females

Why are females choosey?

Direct benefit:

Parental care:

Giant water bug

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Males provides parental care

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Female lays eggs on back of male bug

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Males look after eggs

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Females look for large males to place eggs on back

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Allows eggs to be oxygenated in water

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Female and eggs can avoid predation

Resources:

Black tipped hanging fly

Refuse to mate with male with small gift Short mating duration if gift is small

Male collects fly instead of eating it Male hangs upside down

Exudes pheromonal cues to attract females who may come

Females will only mate with male if fly is big- they will eat then mate Duration is affected by how big the gift is

Males offer direct gift for access to female gametes Nuptial gift

Small gift = less time to mate

As gift gets bigger females offer longer opportunities for copulation Copulation can be up to 20-25 minutes then plateaus

Longer they mate = more sperm transferred from spermathecal duct No more sperm transferred across at certain point

Selective pressure on male to have big nuptial gift Female choosiness based on nuptial gift

Choosiness has a direct effect on female fecundity

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Greater egg production

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Enhanced survival

Indirect benefit:

Fisher Runaway sexual selection

Female preference Male trait

Assortative mating

3 75 120

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Peacocks Male trait:

• Increases attractiveness

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Increase reproductive success

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Reduce survival from tail Female preference:

• Sons inherit trait

• Daughters inherit preference

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Males express genes for showy tail

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Son and daughter will inherit this

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Creates a linkage between traits and preference

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Males with long showy tail get more females and females have preference for males with showy tails

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These reinforce each other

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Long tailed males do better than short tailed males- genes spread for showy tail Preliminary stage:

Having a long tail could be seen as being good for flying

Established- process – traits more exaggerated- son inherit this genes

If it is too disadvantageous in terms of survival then natural selection will balance this out Advantages:

Male:

• He will father more offspring Female:

• Her sons will inherit the trait Empirical support?

Male traits evolve under the opposing forces of natural and sexual selection This results in the correlated evolution of the female preference

Widow bird

Tail length of males manipulated

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• ¼ tail cut short

• ¼ tail artificially elongated • ¼ control

• ¼ control tail chopped off then put back on again Before:

Similar numbers After:

Longer tail increased reproductive success

Tail shorted- massive decrease- fewer nests- less attractive

Females making decision purely off tail and they we can see

Heritable variation in traits Heritable variation in preferences

Assortative mating generates an association between trait and preference Females that like males who are showy will mate with showy males Male trait:

• Increases attractiveness Female preference: • Sons inherit trait

• Daughters inherit preference

Good genes (Hamilton & Zuk 1982)

Good genes argument

Male’s attractiveness is an indication of his survivorship qualities and reproductive potential attractiveness is linked to good genes

Lekking

Lek- aggregation of males on small mating terriorireis Capercaillie- great-tailed grackles

Males provide no resources or parental care. So what do females choose? Males aggregate

Each male defends tiny territory (no resources) Males advertise elaborative displays

Skewed mating success

Females mate with most showy males

Males can’t economically defend females or the resources they require Grouse that lek are spp with biggest home range

Fallow deer lek at high pop density, but defend territory/hareems at low densities (when defending is more economic)

When does lekking occur

Males cannot defend economically the females or the resources they require

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Fallow deer:

• Lek at high densities

• Defend territory/females at low (when economically sensible)

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Grouse spp

References

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