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 HeritabilityCompetition- 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
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 dimorphismDimorphism
Di- twoMorph- form/shape Examples
Stag beetles Odontolabis femoralis
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Elongated mandibles-
Fighting displaying using mandibles-
Allows access to females when in competition with other males PeacocksGenders differ in morphology and behaviour
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Females- drab in colour-
Males- long colourful tail with eye spots Males display tail to attract matesTail doesn’t help with flight Mallard
Female- dull in colour Male- colourful
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Not camouflaged-
Reduction in survival potential-
Invested a lot in glossy plumages-
Lots of carotenoids and other chemicals-
Costly to maintain-
To maintain needs to be in good health ChickensDemonstrate different displays Males:
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Shiny glossy plumage and tail-
Spurs on back of feet- cock fighting –access to females-
Cone- erectile tissuesSexual 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:
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 offspringHer 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-
Female lays eggs on back of male bug-
Males look after eggs-
Females look for large males to place eggs on back-
Allows eggs to be oxygenated in water-
Female and eggs can avoid predationResources:
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-
Enhanced survivalIndirect benefit:
Fisher Runaway sexual selection
Female preference Male trait
Assortative mating
3 75 120
Peacocks Male trait:
• Increases attractiveness
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Increase reproductive success-
Reduce survival from tail Female preference:• Sons inherit trait
• Daughters inherit preference
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Males express genes for showy tail-
Son and daughter will inherit this-
Creates a linkage between traits and preference-
Males with long showy tail get more females and females have preference for males with showy tails-
These reinforce each other-
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)