MBIO317Z Flashcards
Tinbergen’s questions
-causation (e.g.hormones) and development (e.g.learning) = proximate, how questions?
-function (e.g.fitness) and evolution (e.g.fossils) = ultimate, why questions?
function
the fitness value of a behaviour
fitness
relative number of genes contributed to the next generation
natural selection (NS)
-differential survival of alternative alleles
-responsible for how animals look (morphology) and how they work (physiology)
drosophila, genes & behaviour
-normally mate for 20 minutes
-mating time regulated by mechanoreceptors in the males penis
-add a mutation that produces different amounts of receptors
-fewer: don’t know when to stop mating
-too many: don’t mate for long enough
garter snakes, genes & behaviour
-coastal and inland snake populations feed on different prey
-coastal snakes eat slugs, inland snakes refuse them
-some differences seen in lab reared snakes
‘group selection’ : proposed mechanism
-works at group level not individual
-groups of unselfish individuals do better than groups of selfish individuals
inclusive fitness
number of genes contributed to the next generation
ecology
-normal biotic and abiotic factors
-usefullness of many traits is frequency dependant
behavioural ecology
-the study of how behavioural traits maximise fitness
-behaviour
-ecology
-evolution
heterotrophs
energy and nutrients from consuming other organisms
optimal foragers should;
-maximise energy intake
-minimise fluctuations on energy intake
-maximise energy intake during certain periods
sticklebacks
-feed them neomysis in lab
-large sticklebacks eat large neomysis
-optimal prey size half the size of the inside of predators mouth
efficient foragers must ‘make decisions’
- What type of food to eat
- Where & how long to search for food
- What type of search path to use
- How to minimise risk
equation
A model of prey selection
-profitability = E ÷ H
where E = energy gained
and H = handling time
prey selection
efficient foragers chose they prey that gives the highest ratio of ;
Profit (energy) : Effort (handling time)
Marine iguana
-different foraging strategy dependent on body size
-inter-tidal : <1.2 Kg
-small animal cools faster due to smaller surface
area
-not very good swimmers so smaller individuals
use more energy swimming
-sub-tidal : <1.8Kg
-both : 1.2-1.8Kg
what type of search pattern to use
-straight line good to cover a lot of ground quickly
-hostile environment
-might miss resources
-pattern with lots of turns may allow well known areas to be exploited better
painted turtles
-riverline catchments
-move between different streams over land
-mostly moving in straight line
-when in new river, move more randomly
minimise risks : sand goby
-prey on small crustaceans, preyed on by larger fish (cod)
-starved goby foraged more than fed one
-chemical info important, forage less when predator present
-use hinger and predator info together
-hungry animals take more risks
bee waggle dance
-transfer information to other members of the group
-location of pollen source
-duration of waggle says how far away source is
sexually selected signals
-advertise male quality to females
-selected under preferences of females
-ornaments
-zebra finch ; more orange, more attractive to female
agonistic signals
-fighting/conflict
-fiddler crab ; male has large claw, waves it to get someone away from territory
-red deer; roar to say how good the are at fighting
conventional and costly signals : fiddler crab
conventional: size, structure
costly: energy required to raise large claw
iridescent colouration in butterflies
-genus amorphous
-iridescent blue
-catch sunlight during displays, sends out flashing light
-warning their rivals
aposematic (warning) colouration
-poison arrow frogs
-colours memorable
-warning to predators (don’t eat me)
-yellow/black stripes trigger response in vertebrates to not eat them
-hoverfly, a bumblebee batsman mimic
plant to animal communication
-insects see in UV light
-plants evolved under this selection pressure
-different look under UV light to attract pollinators
signals
“information carriers”
a trait that evolved to transmit information
defining communication 1
communication occurs when…
-the behaviour of one animal influences the behaviour of another
-but not by direct action
-by supplying information
brood communication definition
-the transmission of information
-not necessarily a signal
visual signal
fast, short, can have high to low directionality
acoustic signal
medium speed, short, high to low directionality
chemical signal
slow, long, high to low directionality
multi-component signal; ladybirds
aposematic colouring, taste and smell
multi-component signal; Red Jungle Fowl
sexual displays with sound and vision
wattle around head
make a lot of noise
unintended recipients
communication networks
unintended recipients might see signal and send one back
eavesdropping in Siamese Fighting Fish
-pre-fighting signalling phase
-2 males signalling to each other
-can third male take information from that?
-agonistic signal
-swim up and down and wag tail
-open opercular
Siamese fighting fish experiment
-tank with 5 individuals
-separated by dividers that can be moved
-centre individual = eavesdropper
-see others fighting but they can’t see him
-learns to recognise each stimulus fish
-remove opaque barrier separating 2 stimulus fish so they can see each other
-one will win and take territory close to barrier
-other fish cowers away
ritualisation
assumes both sender and receiver benefit
behaviour that initially contains some information evolves into a signal
evolution of ritualised behaviour
- intention movement
- displacement activities
-birds about to fight start grooming as they don’t
know what to do - autonomic responses
-cats hair stands on end ; saying back off
sensory exploitation
-conflict of interests
-exploitation of existing ‘sensory bias’
-male spiders stimulate prey sensing receptors in females
-lure in angler fish exploits predatory behaviour in prey
-hover-flies exploit birds pre-existing bias of not eating yellow stripey things
sales resistance
less likely to be taken in by something everyone could do
deceptive signals
-i.e. in mimicry
-if evolved by sensory exploitation, might be deceptive
-limits on how much deception you can get away with
-receivers under constant selection pressure to not be taken in by deception
costly signals
-signals are costly to perform/maintain
-only high quality individuals can afford all costs
zebra finch;
-orange colour costly
-more orange beak, shows better quality
-better forager etc
Zahavi’s handicap principle
-train in male pea fowl makes it harder to fly, but advertises quality to females
-roaring in male red Der uses energy but advertises fighting ability to competitors
-stotting in Thompsons gazelle ; doesn’t get them further away from predator, but shows athletic ability
anoles lizard
sit and wait predators
costly;
-time waiting
-time it takes to capture prey
-reveals itself to predators & prey
-energy to capture prey
optimality approach
economics of prey choice;
-eat item in front of you or look for another one
-patch residence time
costs, benefits and optima graph
-start with axis, build up layers of complexity as you go
-height of line etc determined by environment
-pink are, benefits exceed costs
-digestive contraints affect linear plateau
costs benefits & optima
cost minimisation strategy ; bare minimum to stay in benefit
optimum point at which benefit-cost is maximised; net rate of energy intake
maximise benefits; biggest difference between black & red line
chosing musclces
economic of prey choice
-unlimited muscles
-range of different sizes to chose from
-ignored really large and really small
-chose intermediate size
-small muscles very low profitability
-large muscles, too much energy to crack open
brown bears
-dont always eat whole fish
-if in abundance, don’t waste time eating nutrient free muscle
-e.g. only eat roe of the females
patch residence time, green turtles
has to move from patch of sea grass to the next
how long should they stay at each patch?
patch residence time assumptions
-food depletion
-as you eat at patch, becomes les and less of it until it Is no longer viable
-diminishing returns
-to start, loads and loads, but as abundance reduces, harder to find food
-currency = net rate of energy intake
patch residence time solutions
-eat one mouthful per patch and then move
-too costly in terms of travel
-eat everything at patch and the move
-problem of diminishing returns
optimal residence time
determined by several factors ;
-travel time between patches
-diminishing returns on foraging efficiency with increased resident time
maximising energy gain over time
-energy/time
-graphically answer given by curve
-long travel time, long patch residence
-short travel time, short patch residence
MVT
=marginal value theorem
applied to numerous behavioural traits;
-duration of mating
-mate guarding
-trade-off between size and number of offspring
-diving patterns in air-breathing mammals
optimality theory criticisms
-evolution does not produce perfection
-panglosian paradigm, well adapted not perfect
-other ways to come to solution, not just maths
-foraging is only one thing animal has to do
-dugongs alter foraging behaviour when sharks are around
contest behaviour
-members of same species compete for access to resources
-exclude opponent from resource
-agonistic, aggressive, fighting behaviour
-intra-specific
giraffes
-long neck evolved as weapons for males to fight over access to females
-akull and vertebrate heavily armoured in makes
-male neck mass increases with age
-giraffes prefer to eat low level shrubbery
behavioural adaptations for aggression
-communication ; signals and displays
-fighting
-trials of strength
-injuries
-fatalities
morphological adaptations for aggression
-ornaments
-colouration
-weapons
-large body size
male characters
red deer contest
-same sex groups until rut in October
-shed antlers after rut and re-grow them
-males agonistic signal = groaning
-compete to win guard of harem of females
structure of red deer contests
- roaring, rate varies, tiring
- parallel walking, allows more accurate description of body size
- antler pushing , strength
-sometimes roaring or parallel walking is enough to settle a fight
how do red deer contests end
-2/3 start with roaring
-majority fights start with roaring, most go on to parallel walk and ~30% fight
-communication important
fighting signals
what information do they contain?
-telling opponent how much you want to win
-advertise ability, not duration
-saying how long you can fight is a bad idea as tells opponent how long they need to last
-try to persuade rival to give up
badges of status
in groups, dominants often have morphological badges that indicate status
not costly to produce
Harris’ sparrow
-making black feathers is costly
-painted subordinate individuals to make them look dominant
-wouldnt work as eventually have to back up signal
escalation in siamese fighting fish
a) lateral orientation
b) tail-beating
c) frontal orientation
d) biting
e) mouth wrestling
f) chasing
signals aren’t always enough
-fighting more prolonged and dangerous the contestants are closely matched
-cant assess opponent and make decisions based on signals alone
mule deer
don’t live as long as red deer so if don’t breed in one season, might not get chance
narwhals
tusk is canine tooth that keeps growing and pierces top lip
-only present in male
elephant seal
-proportion of fights will keep going until one dies
-so wether individual would rather die than back down?
if lose fight, don’t get to reproduce
serious fights
in contests defined by communication or wrestling, the key factor is assessment
-serious fights with injuries are rare and only occur when rewards are greater than costs
statistics
fatal fighting
-10% of male mule deer are injured in fights each year
-60%+ male narwhals have injuries from fights at one point in their life
-5-10% male musk ox die in head to head collisions
fatal fighting in polymorphic fig wasps
-all eggs hatch inside figs
-2 male morphs, wingless fighters and winged dispersers
-wingless males large mandibles to decapitate rivals: 77% dead
-remaining males will mate with females in fig
chance of winning
relative RHP
in any given fight, absolute RHP is not going to determine whether you win
-actual chance of winning varies between contests
-depends on ability relative to opponent
ownership
-male lions compete aggressively for oestrus females
-but among pride males ‘ownership’ is respected
-if equal in size and age, males already with an oestrus female will not be challenged
-following take over, chance of reproductive success is very low : 1/3000
resident advantage
- residents are better fighters
- residents have more to lose so fight harder when challenged
- the winner is decided arbitrarily e.g. mechanical advantage
- experiments with greta tits support 2
- experiments with fiddler crabs support 3
sexual selection and contest
many male sexually selected traits are characters that enhance an individuals ability in male-male competition;
a. large body size
b. elaborate plumage
c. complex song
- not all fights over access to mates
frequency dependence
benefit of a strategy depends on opponent strategy
strategies
-contestants chose from defined set of strategies
-overall ‘plan of action’
-deer fights, strategy is to roar, parallel walk then antler wrestle
-different from tactics
tactic
how to implement game plan in contest
evolutionary games theory
-what should natural selection chose over evolutionary time
-ESS
steps to analysing fighting games
- specify the alternative strategy
- specify the average pay-off for each alternative
- find the expected solution
-> ESS
the hawk dove game ; the strategy
-1975
-not actual hawks and doves
-doves; always display but never fight
-hawks; only withdraw when injured, always fight
-dove v dove, always use displays
hawk dove game: pay-off
- E= pay-off (varies according to what opponent does
- V = (+), value of resource
- C = (-), cost on injury (injury will reduce fitness)
hawk-dove game : E
-H v H = 50% chance of winning, but 50% risk of injury
-H v D = H always wins
-D v H = no injury, no win
-D v D = no injury, 50% chance of winning
H D games
‘pay-off matrix’
-H v H = 1/2 (V+C)
-H v D = V
-D v H = 0
-D v D = 1/2(V)
hawk dove game ; solution
-the ESS
when adopted by all members, population cannot be invade by mutant alternative
all individuals playing hawk, mutant dove would not do well
ancestral population of doves
-average pay-off = 25
-hawk mutation would invade because h v d= 50
-dove is not ess
ancestral population of hawks
-average pay-off = 12.5
-dove mutation cannot invade because when d meets h, pay-off = 0
-hawk = ESS when V>C
C>V: mixed ESS
-proportion of individuals play hawk, the rest play dove
-(or) all individuals play hawk sometimes, dove the rest of the time
-ratio depends on difference between V and C
ESS is not the optimal strategy
-at ESS average pay-off to hawks and doves is 12.5/contest
-optimal strategy would be all doves
-but, not ESS as can be invaded by hawks
H - D fight asymmetries
-hawk-dove game assumes symmetric contests
-opponents place same value of resource
-opponents equal RHP
-but, not usually the case
-there is differences in fighting ability between opponents
RHP
Resource Holding Potential
assessor strategy
assess opponents RHP
play hawk if stronger, dove if weaker
how often assesor wins
assessor winning ability
-assessor strategy, chose to play hawk or dove dependant on strength
-A= assessor
-assessors win 3/4 of resources all together
-assessors can invade populations of both doves and hawks
-pure ESS of assessor strategy
E(A,A) = 1/2V
-E= pay-off
when an assessor meets an assessor they have a 50% chance of winning and no chance of injury
E(H,A) = 1/2(V+C)
hawk will always fight and the assessor will fight or run away
so hawks have 50% chance of winning and 50% chance of injury
E(D,A) = 1/4 V
-half the time, dove has better RHP
-both play dove, dove wins half of these
-half the time, dove has lower RHP
-assessor plays hawk, dove always loses but receives no injury
-overall dove wins 1/2 contests when stronger, none when weaker
E(A,H) = 1/2V
-assessor will have higher RHP half the time, and win those fights
when lower RHP, assessor plays dove and loses without injury
E(A,D) = 3/4V
-half the time, assessor has better RHP
-assessor wins all of these playing hawk
-half the time, assessor has lower RHP
-wins half of these playing dove
-assessor wins half contests when weaker, all when stronger
H-D-A games ‘pure ESS’
-in a population of assessors the average pay-off is 25
-assessor is stable against invasion of doves and hawks
-playing assessor all the time is the ESS
Hawk-dove-bourgeois game
bourgeois strategy is to respect ownership
similar results to H-D-A
bourgeois is the ESS when C>V
real hawks and doves
an over simplification
assumes displays are free
makes some predictions that are upheld by observation of nature
anisogamy
-different sized gametes
-used to define ‘male’ and ‘female’
-‘macrogametic’ : female egg, seeds etc
-large, expensive, fewer in number
-‘microgametic’ : male, small, cheap, millions produced
Batemans principle
1948
-consequences if disparity in gamete size
-darwinian ideas in context of genetics
egg limited
drosophila mating
-in tubes
-isolated male = 0 offspring
-male + 1 female = 30 to 40 offspring
-male + 2 females = double
-male + 3 females = triple (double again)
-female mating with multiple males sees no difference in offspring produced
-egg limited
male tactics
mate with as many females as possible to fertilise maximum number of ova
sperm is cheap and seldom a limiting factor in reproduction, so males often less choosy with mates
sexual dimorphism in primates
-differences in size between males and females
-Lemurs, Indri etc
-1 male per female, relatively same size as each other
-baboons etc
-2-3 females per male, so strong selection for bigger size in male
-higher number of potential mates, higher selection for sexual dimorphism
elephant seals chance of mating
-highly skewed distribution of males fitness due to competition
-highest ranked seal produces a lot of offspring
-2nd ranked, not even a fraction
-some never get to mate, as when rank goes down, so does mating success
male tactics: when to be choosy
-if they have high parental investment
-female quality important for rearing offspring
-pair bonds constrain number of mates and EPCs per male
precedence etc
types of sperm competition
-sperm precedence
-benefit of being first or last
-typically first in mammals
-raffle
-more sperm, more likely to fertilise
-displacement
-remove sperm of other individuals
sperm removal example dunnock
male dunnoqcks peck females cloaca to stimulate ejection of sperm
sperm competition in damselflies
-females mate with several and actively promote male-male competition
-males have sperm scoops on their penis
-removes over 90% previous males sperm before releasing own gametes
-last male fertilises most eggs
mate guarding white fronted beeeaters
-males increase frequency of mating with partner prior to egg laying ; sperm competition
-males spend more time near partner prior to egg laying ; reduces EPCs ten-fold
-after egg-laying, males pursue EPCs; females too busy incubating
nuptial gifts
-‘gifts to the bride’
-used to attract mates and convince them to copulate -honest signals, need to be costly
-low quality males can’t do it
-females katydids often eat the spermatophore
-healthy females incorporate protein into eggs, weak ones use it to increase health
spiders
the ultimate nuptial gift
-redback male spiders jump into females mouth to induce feeding
-well fed females less likely to re-mate
-male soma increases size of egg mass
-soma=body
-finding another female is difficult to low population density
-so males have nothing to lose
female tactics
-eggs costly and in limited supply
-females should be choosy and only mate with high quality males
-female reproductive success is limited by quality of offspring
-sometimes by parental care
-hoping high quality male will produce high quality offspring
criteria of females choice
-large body size, bright colouration, elaborate ornaments
-signals of male quality
-female peacocks that mate with better males lay more eggs, larger eggs and have offspring with higher growth rates
widow birds
-males have long tails
-females prefer males with longer tails
-elongated tails, double to reproductive success
gametes
problems for Bateman
-males can be sperm limited
-can’t explain everything
-female ECP
-monogamy
-polyandry
-male mate choice
-sex role reversal
-anisogamy not reason for everything
epc
female collard lizard
-females have higher hatching success if they mate with multiple males
-higher fitness
why should females seek ECPs
-fertility insurance
-acquisition of nutrients
-parental care
-avoidance of harassment
-change of partner
-genetic diversity
-good genes
-sexy sons
-avoid male harassment
-check out available talent
monogamy
stable social pair bond between one male and one female
polygyny
‘many wives/husbands’
stable social systems with ‘pair’ bonds between multiple individuals
monogamous systems
-male/female together for period of time
-can go off to other individuals, but come back together
-sometimes pays partners to mate monogamously
-pair bonds correlate with reproductive success
-longer together more reproductive success
female distribution theory
potential for polygyny depends on female distribution -dispersed females cannot be defended
female defence polygyny
-male defends group of females
-male size very important
-selected for large body size to aid in defence
-common mating system in males e.g. gorillas, red deer etc
-in coriphidae, males much larger than females so that they can carry them around
male behaviours
coriphidae
-siphohoecetive amphipods
-live in cases made of sand and shell fragments
-males collect females and glue their shells to their own
nesting
montoezyma oropendolas
-nest colonially
-anti-predator strategy
-domiant males defend colony excluding all other males
-gets 80% of copulations
-dominant male shifts if females move the colony
resource defence polygyny
-Males defend clumped resource that attracts several females
-food, territories, breeding sites etc
-polygyny in birds typically due to resource defence polygyny
-can defend any females in its territory
shells
cichlid
-małe cichlid collects snail shells
-tiny females lay eggs in shells
-males huge; 12 times larger than females
-male size correlated with reproductive success
-large males have up to 100 shells and 30 females
-sexual dimorphism
benefits and skews in sex ratio
polygyny and female choice
-benefit of polygyny differs between sexes
-some males benefit greatly, but not all
-look at skew in male mating success
-females have little to gain and may lose resources or parental care
-unmated males difficult to lose
male care, resource abundance
no cost to polygyny
if males provide no parental care there may be no sexual-conflict over polygyny
cost of polygyny to females may be zero if resources are super abundant
what are others doing
polygyny threshold model
best possible strategy depends on what others are doing
when resources are limited females should mate monogamously on high quality territories
mating options for females wiith restricted mates
limited resources ; remaining options
1) mate polygynously on high quality territories
-females accept polygyny because benefit more from being polygynous on high quality territory than monogamous on low quality
2) mate monogamously on poor territory
payment?
problems with PTM
-ideal free assumptions invalid in some cases
-if ideal, at equilibrium all individuals should have the same pay-off
-not free
-resident female doesn’t want additional females as they will have reduced fitness
sexy son hypothesis
-good genes argument
-provide high offspring survival
-females can still benefit from polygyny
-mate with high quality male with hope son will have some characteristics
-sons with greater ability to be polygynous
-little evidence, low heritability
deception
female may not know male is already mated
but once she has laid clutch and male has deserted, its too late to remate
polygyny is the best of the bad job
deception hypothesis
pied flycatchers
females support deception hypothesis
males sneak off to mate with other female, then goes back to primary female
secondary female has to rear alone
many males
social polyandry
-polygyny more common due to anisogamy
-not just mating with many males, but socially bonding with them
-male, some chance of being father of offspring
-sex ratio normally 50/50
electus parrots
-up to 7 males form stable pair bond with one female and help raise 1 or 2 offspring
-typically one male father of chicks in one year
-operational sex ratio skewed by female mortality and scarcity of next holes
males in female role
sex-role reversal polyandry
-males provide all parental care
-males are choosy
-females are larger and have elaborate secondary sexual characteristics
-females have higher fitness than males
sex reversal
sequential polyandry; spotted sandpipers
-females arrive on breeding grounds before males and fight for territories
-small males incubate clutch while female defends territory and courts second male
sperm competition
why do males accept polyandry
-low cost to parental care
-male bias in sex ratio
-first male paternity in 2nd brood
-females store sperm
-secondary male might father offspring that aren’t his -polyandry is best of a bad job for 2nd male
coutship calls
tungara frogs
variable courtship call
if lots of competition, male can scale up call to make it more attractive with ‘chucks’
but, more attractive call makes male more vulnerable
bat more early localise frog when it gives whine and chuck
predation environments
guppies in trinidad
-guppies live in streams that differ in predators they have to contend with
-some stream sections are high predator environments (HP) other low predation (LP)
predation effects guppies
predation affects appearance and behaviour
HP males smaller and more drab than LP
HP males invest less in courtship
HP guppies shoal more
experience
innate recognition
-learning requires experience, but experience can be fatal
-‘know your enemy’
-visual cues in birds and fish
-chemical cues in fish and amphibians
-auditory cues in brush turkeys
crickets warning eggs
maternal effects
-female field crickets exposed to the predators cues warn eggs before laying
-when offspring tested, exposed offspring were more wary than controls
-survivorship greater in exposed group
learning
cues
-learn socially by learning others responses to visual or chemical cues
-relies on classical conditioning - response to conspecific alarm is hardwired
-chemical cues often used - allows long range learning
risk averse behaviours
balance response to risk
-risk averse behaviour can be costly, so can risk prone behaviour
-need to identify and respond
-don’t run, not a predator = true negative
-run, not predator = false positive
- don’t run, predator = false negative
- run, predator = true positive
predator inspection
approach a threatening organism in their habitat and gather information about;
~ level of satiety
~its prey preference
prey animal can assess level of risk
(and examples)
crypsis
-camouflage
-match background, not just visual can be auditory
-moths fuzzy to protect against echolocation
-only works effectively if animals move at the same speed as background
-stick insect, blow on it and it will sway like breeze to blend in with environment
masquerade
camouflage without crypts
looks like something you don’t eat to eat
resembling inedible object
refugia
-coexisting
-going to part of habitat predator can’t follow
-clownfish: anemones
-shrimp cleaning goby’s home
-frilled lizard, eye spots
non-visual (auditory)
dietetic displays
-can be non-visual e.g. auditory
-some animals produce distress calls, but these are not recruitment calls
-peacock butterflies produce hissing sounds and high-intensity ultrasonic clicks and cause predatory rodents to flee
chemical defences
deterent used by small, delicious animals
not many mammals, but skunks impressive
some smells make animals easier to find
aposematism
signalling poisonousness
widespread - nudibranchs, sea snakes, caterpillars and many others
important to be conspicuous
mullein mimicry
two or more unpalatable species converge to look similar, gain great benefit
batesian mimicry
edible or palatable species resemble an inedible species. success is frequency dependant
rapid locomotion
-prey animals adopted to move fast
-lepidopterans ; fast flying species more likely to survive attack
-trade-off; fast flying insects may have to devote up to half of body mass for flight muscle
lizard+insect
misdirect predators attack
lizard: sheds tail, tail wriggles to misdirect predator
insects: false heads, 180º after landing to confuse birds
what do they release?
sea hares
-when attacked, release 2 chemicals
1. a purple ink
2. sticky substance called opaline
-ink contains amino acids and is highly attractive
-opaline deactivates chemical senses of the attacker
dead
thanatosis
-be less appealing, play dead
-many species engage in this including; lizards, moulting spiders etc
-virginia opossum backs up its signal
*heart rate drops, body goes floppy, starts drooling and urinates
ambush
-stealth, crypisis and limited movement
-not just visual crypts, also scent
*dog rolling in faeces
-assassin bugs
*disguised visually and chemically
*use prey debris and plant resin
spiderwebs
trap builders
-ant lions dig pits
-spider webs; use glue & electric charge
*web has negative charge
*insects (flying) pick up positive charge
~stick to web
tentacled snakes
-use feint attacks to manipulate escape responses of fish prey
-gets into position and initiates fake attack with middle of their body
-fish elicits escape response in wrong direction - directly into snakes mouth
pursuit
-relies on speed and endurance
-sometimes referred to as persistence hunting
-effective, but aerobic muscle is not good for hunting
-wild dogs have higher capture rate, but often lose prey to larger carnivores
-chase in high heats until predator passes out
predator adaptations specifics
-orcas different colours/patterns/types dependant on prey type
-great tits eat parts of sleeping bats
-grasshopper mice howl to attract prey, then jump on back of spraying beetle to prevent being sprayed
mantis shrimp
-punch through shells
-heavily modified 2nd leg
birds+mammals+fish
patterns of parental care and mating systems
birds: typically male and female parental care with majority being monogamous
mammals: female parental care and typical polygynous mating
fish: male parental care, polygynous, polyandrous, polygynandrous
dunnock mating systems
variable mating system
monogamy: biparental care
polygyny: male helps 2 females in proportion to mating
polyandry: 2 males care at 1 nest, in proportion to mating
parental care - mammals
polygyny common
female uniparental care in 95% species
*prolonged gestation, mammary glands
males could protect and feed females
*but they spend most time mating with additional females
parental care - fish
most show no parental care
male care common with external fetilisation
female care common with internal fertilisation
sexual conflict and parental care
*in many cases, benefits either parent to desert
*4 possible outcomes;
-no parental care
-female only care
-male only care
-biparental care
how fertilisation happens
certainty of paternity hypothesis
-with internal fertilisation, male is unsure of paternity
*less willing to invest parental care
-with external fertilisation, male more confidence in paternity
*but cuckoldry is still possible
paternity rrelated ??
bluegill sunfish
males perform less egg defence if another male was present when eggs were fertilised
in terms of parental care
association hypothesis
-association with eggs or young pre-adapt parent to provide parental care
*to an extent parental care is an exaptation
-males are associated with externally fertilised eggs layed in their territory
*defend eggs and young while defending territory
-females are associated with young when there is internal fertilisation
ESS parental options
Po = probability of egg survival with no care
P1= probability of egg survival with 1 parent
P2 = probability of egg survival with 2 parents
P2> P1> Po
ESS other ratios
p = chance for a deserting male of mating again
W = number of eggs of female deserter
w = number eggs for care giving female
W>w
female and male dessert if:
WP>wP1 (or female will care)
Po (1+p) > P1 (or male will care)
parental desertion favoured if:
W»w
p is large
P0 ≈ P1
female cares and male deserts if
wP1 > Who (or female will desert)
P1 (1+P) > P2 (or male will care)
female only care favoured if:
p is large
W≈w
P1» Po and P2≈P1
female deserts and males care if:
WP1 > wP2 (or female will care)
P1>Po (1+p) (or male will dessert)
male only care if:
W»w
p is small
P1»Po and P2 ≈ P1
female and male care if:
wP2>WP1 (or female will desert)
P2>P1 (1+P) (or male will desert)
biparental care if:
P2»P1
p is small
brood parasite - host coevolution
-evolutionary arms race
-brood parasites evolve adaptations to maximise success e.g. egg mimicry
-hosts evolve tactics to avoid parasitism e.g. egg recognition, aggression towards parasites
intra-specific brood parasitism
-same species acts as host
-over 200 species of birds
-brood parasitism in coots
*females which lack territories parasite territory
holders
*territorial females prioritise neighbours nests
common cuckoo
-inter-specific brood parasite: other species acts as host
-lay eggs in nests of over 100 other species
-only 11 hosts frequently parasitise
-hosts smaller than cuckoo
-females lay mimetic eggs
-individual females are host specialists
what do they do?
European cuckoo
-female cuckoos stake out host nests
-wait until host clutch initiated
-wait near nest before laying
-removes one host egg and lays one egg
-at nest for only 10 seconds
how are they detected?
European cuckoo tactics
-laying tactics prevent detection
-josts aggressive to adult cuckoo near nest
-rejection of cuckoo egg more likely if female cuckoo detected
-reed warblers use social information (alarm calls of neighbours) to detect female cuckoos
young cuckoo
European cuckoo adaptations
adaptations of cuckoo eggs and young;
* shorter incubation times, usually hatch before host eggs
* young cuckoo ejects all other eggs and hatchlings from the nest
* begging calls of cuckoo mimic entire host brood
egg mimicry
cuckoo eggs usually slightly larger than host, but much smaller than would be expected given the size of the cuckoo
discrimination
cuckoo - host coevolution
-most hosts show discrimination of eggs
-degree of mimicry is related to host species’ ability to discriminate
* less discriminate hosts –> lower similarity of parasitic and hosts eggs
* dunnock-cuckoo lays non-mimetic eggs and dunnoqcks don’t reject
why accept parasitic eggs?
-acceptance behaviour may be due to costs of rejection
* accidental damage and ejection
–e.g. reed warblers occasionally throw out or
damage their own eggs
* learning involved in egg recognition
imprinting on eggs
-naive hosts must imprint on their own eggs to distinguish and reject foreign eggs
-experienced birds have a recognition template for their own eggs
* can’t reject parasitic egg without seeing their own eggs
obligate siblicide
-siblicide always occurs e.g Black eagles
-2 egg clutches
-highly asynchronous hatching
-death of junior chick usually 1-2 days after hatching
facultative siblicide
-siblicide sometimes occurs
-galapagos fur seals
*up to 23% females give birth whilst still feeding an older pup
* youngest pup may starve or be killed by older sibling during unfavourable environmental conditions
- also found in egrets, herons, owls, kittiwakes etc
non-lethal sibling aggression requirements
-resources which are limited and monopolizable
-asymmetry in offspring
-non-lethal, but still violent. can lead to death of smallest offspring
piglet non-lethal aggression
-fight for access to treats
-precocial development of canine teeth
-establish hierarchy within hours of birth
P-O conflict
scramble competition
-young compete for position close to parent
-position in nest is an important determinant of who gets fed
-offspring size important determinant of ability to monopolise primary location
begging
offspring use vocal and visual displays to compete for food
– resources allocated to chicks that beg at the highest intensity
non-aggressive brood reduction
-hatching asynchrony leads to size hierarchies in the brood
-asymetries in food allocation
* differences in growth rate & fledgling weight
* mortality of youngest/smallest offspring
p-o conflict parents perspective
offspring alpha and beta are equally related to the parent (r=0.5) and therefore have equal value
p-o conflict offspring alpha perspective
values itself (r=1) twice as much as it values sibling or parent (r=0.5)
Hamiltons rule
-alturism favoured when r B>C
-conflict among kin will arise when demand outstrips supply
p-o conflict numerical example
-mother with 2 dependant young
-mother has 2 indivisible prey items
-eating 1 prey item would increase other offsprings fitness by 4 units
-eating 2 prey items wild increase either offsprings fitness by 7 units
-parental optimum is to share food equally between alpha and beta
optimistic clutch sizes
resource tracking hypothesis
-parents lay optimistic clutch size to capitalise on unpredictably favourable environmental conditions
-in bad years, brood size must be reduced
-hatching asynchrony facilitates brood reduction
replacement offspring hypothesis
-core set of offspring which parents can support and marginal offspring which are expendable
-marginal offspring are a form of insurance incase of egg infertility, mortality etc
-explains obligate siblicide in Nazca Booby
parental favouritism
-baby American coots have orange-tipped feathers on their backs and throats
-orange-tipped chicks fed preferentially
* higher growth rates and survival
* parents use feather colour as a signal
sex ratio
-proportion of individuals that are male
-equal males and females seen in many taxa (0.5)
number of males ÷ number of males + number of females
why 0.5?
-half genes from each sex
-if less of one sex, they will contribute more offspring per capita
-individuals investing in the rare sex will be fitter
-if investing in rare sex is hereditary, alleles for rare offspring will increase in frequency
-eventually ratio will be 0.5 and offspring of both sexes will be equally beneficial
fishers theory of equal investment
-think of theory as a pendulum
-behaving in particular way dependant on how many individuals are also behaving that way
-male biased: fitness of female>male
* selection favours parents who produce females
-female biased: fitness male >female
*selection favours parent that produces males
sex ratio in humans
-1.05 male: 1 female
-unbalance, slightly in favour of males
-males cheaper to make
* less base pairs, one X, one Y
* males more reckless; higher mortality
-overall investment in each sex is equal
assumptions of equal investment
-males and females contribute equally to the gene-pool
-panmaxis: random mating
-equal investment returns (benefit/cost) from offspring of each sex
-theory of equal investment is a non-fisherman model
non-fisherman sex ratios
-get the same back from male and female offspring (equal investment returns)
-if fisher correct, deviation from returns should lead to deviation from 0.5 in investment
-if males and females cost the same, this is equivalent to deviation from 0.5 in sex ratio
local mate competition (LMC)
-if males don’t disperse far, brothers will have to compete for access to females
-‘unsuccessful’ sons are a waste
-when sons compete, average value to mother is reduced
-> mother should favour daughters
theory of LMC acariform mite
-complete isolation of brood, all reproduction occurs inside the mother
-inbreeding, sons fertilise their sisters
-viviparous: live young
-sons die, only females produced
LMC parasitoid wasps
-degree of sex ratio determined by strength of LMC
-females lay eggs in fly pupae, multiple broods can be laid in one pupae
-degree of isolation depends on how many broods played in one host
* more broods, closer sex ratio gets to 0.5
LMC parasitoid wasps : clutch sizes
-only mated females disperse, sons compete to fertilise sisters
-small clutches, male biased
-large clutches, female biased
-number of mothers in pupae increases, clutches get smaller
number of females, number of mothers?
strength of LMC
-variable
-more than 1 female can lay eggs in host
-increasing mothers, strength of LMC declines
-female bias in sex ratio should diminish with increasing number of mothers
-successive mothers produce increasing number of males
ephemeral
don’t stay in same place after mating occurs (or, short-lived)
LMC assumes
- offspring mature in discrete ephemeral groups
- mating only within these groups
- only mated females disperse
Local resource competition (LCR)
-resources other than mates e.g. food, shelter
*females compete for access to this
-non-dispersing females subject to LCR
-limited number of females can survive, so no point producing excess females
LCR example
-females compete for food in Galago crassicaudatus
-thick tailed bushbaby : male biased sex ratio due to LCR
maternal condition
-fitness of one sec affected by unit of investment
-good maternal condition = more milk
- more milk = bigger offspring
-big males wins more fights
-so male size more beneficial for survival
fitness of males tied to maternal condition more than fitness of females
maternal condition: female quality
-males not fussy about who they mate with
-so poor condition females produce more females, because males don’t care what they look like
-subordinate females also produce more females
host quality
-bigger host = more food and therefore bigger offspring
- in parasites females disperse, big females disperse further
-fitness of females tied to host quality more than fitness of males
host quality: females and mothers
-manipulate quality of host?
-mothers can tell condition of host and adjust sex ratio in response to environment
sex roles
the strategies for mate choice and competition over access to mates that males and females adopt
sex role reversal definition
reversal in the usual mate choice and competitive strategies for access to mates adopted by males and females
sex role reversal can occur if:
reproductive success of females is limited by the rate at which they can access males/male gametes
sex role reversal possible when:
- males invest heavily in parental care
- sex ratio skewed in favour of females
- there is sperm competition
1) males invest heavily in parental care
-costs of reproduction normally higher in females
* gamete production has a greater cost
-total cost of reproduction = gamete production + parental care
Jacanas
-partial sex role reversal
-high rates of egg predation
-females compensate by laying multiple clutches by mating with multiple males
-males incubate
-females hold territories and compete for males
parental care definition
any investment by the parent in an individual offspring that increases the offsprings chance of surviving at the cost of the parents ability to invest in other offspring
pipe fish
-brood pouch in male
-male carries out pregnancy
-male pregnancy is not sex role reversal, it is a cause of it
-males choosy, prefer females with larger skin fold
-females display and are larger
fecundity
ability to produce an abundance of offspring or new growth: fertility
female ornaments and fecundity
pipe fish, positive relationship between amount of blue colouration and number of eggs produced by females
complete sex role reversal in pipe fish
-choosy males, assess female ornaments
-competitive females, inhibition of female ornament development
-polyandry to greatest extent in any animal taxon
Jacanas male paternity costs
-males provide all parental care
-can lose eggs to crocs
-females store sperm
-no guarantee of clutch paternity
-males waste time and energy incubating other males offspring
* up to 70% in highly polyandrous
skewed sex ratio in favour of females
-expected operational sex ratio is 1:1 (=0.5)
-if sex ratio is skewed
*limit on rate most abundant sex can access mates
*could be greater than constraints due to costs of parenthood
*in female biased populations, could lead to sex-role reversal
disproportionally high male mortality due to;
- intra-sexual selection
- increased risk of predation
- sex-ratio distorters
sex ratio distorter
selfish genes transfered exclusively via one sex and fatal to the other sex
wolbachia bacterium
-present in Acrea encedon (butterfly)
infects 80% of females, kills all male embryos
population up to 95% female
do females compete?
-male lekking swarms common in insects
-In female biased populations, females form swarms
-mated females more likely to leave swarm than virgins
-female lekking swarms = female competition
- sperm limitation
-female fertilisation success constrained by supply of sperm
-female reproductive success is limited by rate of access to male gametes
spermatophores
-size increases with male body size
-repeated copulations deplete the supply
-size/number matches female quality
-control over how much sperm you give to the female
-present in crustaceans
sperm limitation in spiny lobsters
-spermatophore provided by male increases with size of female mate
-clutch size increases with spermatophore size
-large females Mae earlier in breeding season
limiting sex
-supplies gametes/mating opportunities at a low rate
-reproductive success determined by quality of mates
-choosy– sexual selection is weak
-usulay females; male in sex-role reversed system
limited sex
-supplies gametes/mating opportunities at a higher rate
-reproductive success determined by rate of accessing mates
-competetive– sexual selection is strong
-usulay males; females in sex role reversed sysystem
male fitness
depends on number of mates and is maximised through promiscuity
females fitness
depends on quality of mates and is maximised through choosiness
sexual conflict over
1) mate guarding by males
2) copulation attempts by unfavored males
3) duration of copulation
4) parental care duties
5) damage to females during fights between males
6) damage to females during mating
7) survival of previous young
8) survival of the male
fight
two individuals adopting different roles; owner of resource and intruder
-conflict normally driven by anisogamy
anisogamy: basis of sexual conflict
in terms of reproduction, behaviour is not cooperative - there is conflict
individuals have evolved to only think of maximising their own fitness
amplexus
mate guarding in amphibians
mating embrace, male positions on back of females and grasps tightly with front legs
1) mate guarding by males
-males only have to subdue females in order to mate
-males maximise fitness by preventing other males from accessing female gametes
-male ownership removes female choice of mate
-females should resist
water striders
-post copulatory mate guarding
-songle female slightly larger than the male
-male stays on top of female after gamete transfer preventing another copulation
-can last a few minutes to several weeks
-in this species, there is always a male ‘riding’ the female
female water striders
-mating is expensive for females
-carrying male elevates metabolic rate
*live male cheaper than dead male
-struggling is also expensive
*more so than carrying male
*leads to 200% increase in metabolic rate
*sustained for 16s before needing rest
water striders grab rates
-on average, single females subjected to 20 grab attempts per hour
-energetic cost of struggling increases with grab attempts per hour
-female decision should depend on guarding and duration of struggle
crustaceans
-pre-copulatory mate guarding
-females can only mate after moulting
-males guard females during pre-moult phase to ensure access to copulation
-mates have capacity to tell when females about to moult
* chemical released
-males fight over ownership of guarded females
costs and benefits male T. thermophilium
-costs
*energy for locomotion
*increased risk of predation
*restricted access to food
-benefits
*access to mates
costs and benefits females T. thermophillium
-costs
*restricted choice of mates
*increased risk of predation
*restricted access to food
-benefits
*none? would get to mate anyway
*males that resist shaking might be high quality
are pre-copular pairs in sexual conflict?
-driven by male-male competition over females
-large males guard females for longer
-is females shaking just a test?
*less time struggling, guarded for longer
*shows female really trying to remove male
*females interest to decrease time being guarded
2) unfavored males
female preference for certain males
unfavored males still want to copulate
physically coerce females
-e.g. in species with sexual size dimorphism
female coping mechanisms
-females solicitate mating with dominant males
-subordinate males try to mate with her
*emit distress call
*dominant male arrives and harms subordinate
-cloaca in birds
*fowl can evert cloaca to eject sperm
manipulating social status
-high ranking male put in group where they become low ranking
*sperm ejection increases
-elevated in rank, sperm less likely to be ejected
-females retain sperm of best quality males
3) duration of copulation
prolonging duration of copulation so more sperm is transferred
does not benefit females
male spermatophore
-6% of body weight
-2 components
*ampula : contains sperm
*spermatophylax : water & amino acids
-amino acid prolongs copulation after male leaves
-females feed on amino acid, makes her sleepy, nampula attached longer
4) parental care duties
-in species with bi-parental care, one parent could benefit by deserting
-offspring receive some care from remaining parent
-extra mating outbalances loss of care to first brood
-deserted parent loses fitness
-plenty females, male deserts
Kentish plovers
female desertion
more males than females so females desert
males lose fitness
females stay if its late in the breeding season or the clutch is very large
North American garter snakes
-end of hibernation, males want to copulate with as many females as possible, even immature ones
-females killed in communal dens
-small females most at risk
-vary hibernation time to avoid males
South American fur seals
-males sexually mature at 4-5 but mating is dominated by 7-9 year olds
-younger males cooperate by dragging female out to sea
-cooperation stops when out at sea, males start fighting over female
-female can accidentally die
6) intentional damage to female during mating
-if mating is dangerous, females avoid remating: reduces risk of sperm displacement
-may reduce female survival: she might release more eggs increasing male paternity
chemical warfare in drosophila
-chemical in male seminal induces hyper-ovulation in females
males get more offspring
females get shortened life
evolution of female resistance to chemicals
bean beetle
-intentional damage
-damages females reproductive tract
releas all gametes they have left?
flatworms
hermaphrodites
shoot sperm at each other to erode epithelium and allow sperm in
can get ripped in half but don’t die
7) survival of previous young
lions:
*males in pride don’t often have conflict
*new pride males can’t take over pride
*kill previous young to bring female into oestrus
*female tries to hide young
lactational amenhoria
in mammals
females can’t come back into oestrus when lactating
orcas: survival of young
male wants to kill neonate to bring mother back into oestrus
females will try t band together to attack male
males mother helps male kill baby orca
8) survival of the male
-sexual canabalism in praying mantis and orb web spiders
-likely when females are larger than male
-when females are predatory
non-metal parasitism
the parasite benefits from relationship, while host pays cost
classic parasites
can be divided into Endo and ectoparasites
isopods attach to tongue of fish and eats it
* fish can use isopod as tongue
* isopod continues to feed on fish
fluke worms
parasitoids
spends portion of development inside host, typically consumes and/or kills host before emerging
free-living life stage
parasites overview
approx 20% all species are parasites
all of us have some kind of parasite at any given time
-living organisms are a landscape or canvas where parasites cab act
-virulence of parasite depends on needs of parasite
black spot disease
when get loads of black spots, other fish don’t want to skool with it
indirect parasitism
* host more likely to be eaten
sacculina and shore crabs
parasitic barnacles
attaches to crab & enters through leg joint
* crab doesn’t know
once crab infected, doesn’t moult again or regenerate lost limbs
crab can’t reproduce
sacculina
-energy diverted from crab reproduction to sacculina
-crab reproductive behaviour co-opted for dispersing sacculina eggs
-egg bearing females groom and clean the egg pouch and fan water over it
* both males and females do this
caterpillars and parasitic wasps
females oviposits into caterpillar
caterpillar continues to develop and feed until larvae emerge
some larvae stay behind
control caterpillar so it will protect larval eggs from predators
emerald cockroach wasp
-delivers 2 stings to cockroach brain
-1st sting causes paralysis
-2nd sting, more precise location, sub-oesophageal ganglia, disables escape reflex
-leads cockroach to hole and lays egg on it
-grun hatches and eats cockroach alive, but in very specific order
malaria
-plasmodium manipulate mosquito in 3 ways
*reduces risky feeding
*interferes with blood drinking
*tinkers with chemosensory system of mosquito
-mosquitos attracted to particular smells
cordyceps
fungus: ant brain jacker
infects ant brain
fungus erupts from ants head
makes ant climb up high, so when fungus erupts, spread is maximised
trophic transmission
animal needs to be eaten for transmission to happen
parasitic flatworm
-adult stage release eggs, excreted by bird
-eggs eaten by snail, hatch into larvae: miracida
-miracidia travel to gut, develop into sporocysts
-brood sacs highly conspicuous to birds, which eat them
parasite conspicuousness
e.g. orange spot causes infected animals to be eaten more frequently
may exploit sensitivity of fish = receiver bias
toxoplasmosis
most successful parasite on earth
starts life in cats
carried by rats and mice
toxoplasma convinces host to be eaten by cat
human behavioural changes:
*slower reaction times
*schizoprhenia
*reckless behaviour
host countermeasure : allo-grooming
many animals allogroom
social functions
*affiliation reinforcement
*reconciliation
*courtship
*bond reinforcement
economic function, traded for food or sex
anting
birds allow ants to move over their feathers removing parasites
some species also crush ants and anoint themselves with formic acid
cleaner fish
smaller fish remove parasites from larger fish, including predators
mutualism : both parasites benefit from coopearating
cleaner wrasse
-client fish held in cages with and without cleaners
-fewer parasites on clients held with cleaners
-wrasse occasionally cheat but overall benefit clients
oxpeckers
-remove echo-parasites from various ungulates
-also drink blood and prevent wounds healing
-excluding/allowing oxpeckers had no effect on parasite levels
-clients wounds took longer to heal when oxpeckers were present
zoopharmacognosy
-ingestion or application of substances to kill parasites or discourage them from setting
-olive baboons eat leaves to kill blood flukes
-brown bears apply osha roots to fur to repel blood feeding insects
birds and nicotine
in Mexico City, birds incorporate cigarette butts into nests
nicotine kills ecto-parasites
number of butts negatively correlated with parasite density
cooperation
a behaviour which provides a benefit to another individual (recipient) and which is selected for because of its beneficial effect on the recipient
many animals appear to act cooperative
-animals e.g. lions, sailfish, hunt in groups
-meerkats act as sentinels allowing others to forage
-social Hymenoptera have non-reproductive individuals which work “for the benefit of the colony?”
prisoners dilema
-2 robbers arrested and held separately. insufficient evidence so each offered a choice;
1. testify against each other and be set free
2. stay silent and serve a short sentence
-don’t know what the other will do
prisoners dilemma pay-off matrix
-prisoner A + B cooperate = 6 months
-A cooperates, B defects = A gets 10 years
-both defect = 5 years
prisoner dilemma as an ESS
cooperation is not an ess
it is the optimal solution overall but rational choice is defection
kin selection
-characteristics favoured due to their beneficial effects on the survival of close relatives
-benefit for offspring and non-descendant kin
*parental care
*feeding siblings
*defence of family territory
*sterile workers
direct fitness
reproduction
indirect fitness
aiding survival and reproduction of non-descendant kin
inclusive fitness
direct + indurent fitness (Hamilton 1964)
coefficient of relatedness (r)
a measure of genetic similarity
descendant kin
*offspring: r=0.5
*grandchildren: r=0.25
*great-grandchildren: r=0.125
non descendant kin
*full sibling: r=0.5
*half sibling, niece/nephew: r=0.25
*cousins: r=0.125
Hamiltons rule
central theorem of inclusive fitness (kin selection)
* predicts social behaviour evolves under specific combinations of relatedness, benefit and cost
* NS favours genetic success
Hamiltons rule : predictions
-predicts when an altruistic gene will be favoured by selection
-if cost to donor is C and benefit to recipient is B, gene will inrease in frequency if :
rB>C
-r= relatedness of recipient to donor
genetic success
passing on of specific genes
reproductive success
=fitness
Hamiltons rule rB>C
-B = 10, C= 2
* offspring: r=1/2, 1/2(10)= 5 5>2 (benefit)
* grandkids: r=1/4 1/4(10)= 2.5 2.5>2 (benefit)
*great grandkids: r=1/8 1/8(10)=1.25 1.25<2 (cost)
cooperation as a by-product
-can arise as byproduct of a selfish act
-cooperation is best option from selfish POV, but also provides benefit to others
-mutualisms in foraging, territory defence, predator detection
cooperative hunting game
-two players share food equally
-solo hunter will be mildly successful (4 units of energy) so each gets 2 units
*hunting costs 1 unit, so pay-off to hunter is 2-1 = 1 unit
-mutual hunting generates higher pay-off (10 units)
*both individuals get 5-1 = 4 units
reciprocity
-humans and primates
-problem of cheating
-can be an ESS under certain conditions
-cooperate for as long as others do
* always copy move of other individuals, but start cooperatively
*optimal strategy
iterate prisoners dilema
best strategy = tit for tat
*cooperate on first iteration; after that do what opponent did on previous move
successful strategies were nice, retaliating, foraging and non-envious
*punish defection, cooperate if opponent cooperates, don’t try to outscore opponent
sharing of blood in vampires
-feed close relatives and unrelated roost mates that fail to find a meal
-donors recognise cheats
-close association in roosts is important
-benefit to the recipient greatly outweighs cost to donor
enforcement on cleaner wrasse
-client fish punish cleaners who feed on them, rather than their parasites, by chasing them or fleeing away
-cleaners are more likely to feed on parasites after being punished
manipulation
-what looks like cooperation on part of the donor may have evolved through the manipulation by the recipient
-inter and intra specific brood parasitism
-some pollination systems e.g. bee orchids
-some seed dispersal systems e.g. burdock fruits
cooperative breeding definition
a system of breeding characterised by the normal presence of helpers at some or all nests
any type of parental behaviour e.g. nest maintenance
helper definiton
an individual that performs parent like behaviour toward young that are not its own offspring
singular breeding
one breeding female per group
plural breeding
two or more breeding females per group, with either seperate or joint nests
social system diversity in CB
-solitary to colonial breeders
-helpers of either sex, related or unrelated to breeders
-monogamous, polyandrous, polygynous, polygynandrous
-mammals often see female helpers, birds often see males
florida scrub jay characteristics
-extremely limited, oak scrub habitat
-critically endangered
-singular breeding
-non-migratory, year round all purpose territory
-relatively long lived
-monogamous
-completely extirpated in southern florida
-great numbers only in state parks
florida scrub jay - cooperative breeding
-offspring delay dispersal for at least 1 year (up to 3 years females, 6 years males)
-offspring are helpers to parents
*e.g. vigilance
*not a lot of habitat for them to disperse to, so stay behind in hope of inheriting territory
cooperative breeding black backed jackal
monogamous pairs
1-3 helpers from previous litters
helpers feed pups and breeding female
helpers increase fitness of breeders
a lot of food, not many places to go, so form big groups
facultative cooperative breeders
capable of breeding as lone pairs and forming extended family groups when conditions (abundant food, limited vacant territories) favour philopatry over dispersal
cooperative breeding dwarf mongoose
-helpers prevented from breeding for 3-4 years by alpha male and female
-stress other females out so much, cause a shift in hormones so they physically can’t breed
-unrelated helpers: waiting to take over breeding territory
-breeding helpers: older helper females may be allowed to breed
pseudopregnant helpers
young females may mate and lactate, but do not give birth
cooperative breeding in anemone fish
clown fish
-pairs defend territories (anemones) and may allow unrelated helpers to assist
-helpers are investing in the long-term take over of the territory
-protandrous hermaphrodites
-either one of breeding pair dies, smaller helper can assume the male role
habitat saturation model
all suitable breeding habitat filled
*individuals forced to delay dispersal
experimentally tested in superb fairy wrens by removal of breeding adults
marginal habitat model
additional constraint is the lack of habitats of marginal quality
* eliminates potential for non-breeding floaters
CB= best of bad job when breeding is limited
benefits of philopatry model
-intra-population variation in breeding territory quality
-individuals born in high quality natal territories have intrinsic reasons to remain home
life history hypothesis
emphasises role of life history in evolution of cooperative breeding
cooperative breeders viewed as being on the K end of the r-K continuum
K end of continuum
delayed maturity, high adult survival, small clutch size, low reproductive rate, low dispersal rate
kin selection and CB
helping may increase production on non-descendant kin
helpers must be closely related to breeders
explain 55% of CB in birds
enhanced survivorship
-helping may increase survivorship until breeding is possible
*large group for defending territory, finding food, detecting predators
-heloing may be form of rent payment to avoid expulsion from territory
territorial inheritance
helpers may inherit territory from breeders or may be able to bud-off a section of territory
coalition formation
larger groups able to retain territory, increasing fitness of all group members
future mate acquisition
if males are in short supply, secondary males may be waiting to become primary males
CB- pied kingfisher
-primary helper is related to breeding pair
-secondary helper is unrelated
*ties to form bond with breeding female s
*48% of secndary males mate this way
theories of lek evolution
6 THEORIES:
-hotshot
-hotspot
-female preference
-reduced predation
-black hole
-kin selection
promiscuity
-mating systems without pair bond formation
-brief encounters between individuals
-single or multiple matings
-males often indiscriminate
-females should still be choosy
*good genes
scramble competition promiscuity
-when females are widely scattered, males compete to find and mate first with females
-horseshoe crabs mate in extreme breeding assemblages a few nights a year
*males in good condition arrive attached to females
*males in bad condition act as satellites
promiscuity and male influence
-male benefits if female doesn’t mate with other males
-nuptial gifts can influence female behaviour
-sperm competition very important with multiple matings
Leks definition
-aggregations where males defend small display territories
-displays typically energetically expensive and elaborate
promiscuous mating system
no pair bonds
males provide no parental care
females only gain sperm
lek example
-mammals around 12 species: ungulates, pinnipeds, bats
-birds around 150: waders, grouse, hummingbirds, cotingas, manakins, birds of paradise, kakapo
-marine iguana
-similar systems in fish, amphins & insects; only recently refered to as leks
white-bearded manakin leks
-males each defend a sapling and bare patch of ground they have cleared
*70 display areas in 150m2
*display: rapid perch change, snapping wings
-female choses male, mates and leaves
-alpha male, number 1 male on lek has way over 70% of matings
-quite long lived, so alpha one year likely to be alpha again next year
hotspot hypothesis
-males aggregate where they are most likely to encounter females
-where there are large numbers of females, find large numbers of males
-driven by female distribution
-males are conforming to an IFD driven by female distribution
IFD
=ideal free distribution
hotspot hypothesis examples
-walruses wait near feeding areas
-male New Zealand lesser short-tailed bats form singing roosts close to communal roosts
-females have very large foraging ranges, but always return to the communal day roosts
hotshot hypothesis
leks from around alpha male
subordinate males are making the best of a bad job
cluster around hotshot male hoping to get an occasional copulation
best place to be is right next to the most attractive male
female preference hypothesis
-males form a group to stimulate females
-fmelaes may not breed until they have ‘shopped around’
-if female sees couple of attractive males displaying, unlikely to mate with them as can’t compare across range of males
-males forded to aggregate to allow females to ‘check out the talent’
-really large leks should be the most successful
black hole model
also called female harassment model
-females go to leks, because when on them they encounter older more experienced males that won’t harass them
-use leks as shelter
-no preference for lek position or male quality
kin selection and leks
-the evolution of characteristics which favour the survival and reproduction of close relatives
-individuals displaying on shared leks or leks in close proximity to one another, are sometimes related
-but on most leks, males are unrelated
uganda kob
perfectly linear relationship between lek size and females visiting
-contradicts female preference hypothesis
-if correct, we would expect small leks to have almost no visits
topi
are females harassed less on leks?
oestrus female topi chased most when on leks
contradicts black hole hypothesis
ruffs
-leks located near pools where females go to feed
*supposts hotspot hypothesis
-within leks, spatially structured
*subordinates close to alpha male have higher fitness
*supports hotshot hypothesis
behaviour
everything an animal does
horses and dogs can read human facial expressions
innate behaviour
that which the animal in born to perform, sometimes refered to as instinctive
learned behaviour
that which develops as the animal grows and gathers experience
-caveat: pften no hard and fast distinction between learned and innate
paedomorphisis
retaining juvenile characteristics in adulthoodh
behaviours: why them happen
-often have a trigger e.g. fixed action patterns occur in response to a sign stimulus
*sign stimulus -> releasing mechanism ->FAP
-releasing mechanism isa neural pathway
-fixed action pattern (FAP) is behavioural response
-sometimes in the wild mother who lost cubs adopt other baby animals (nurture response)
example - sexual attraction in sticklebacks
-tinbergen experiment
-different male shape and colour configurations to determine what females were responding to
-females respond to red underside, not whole male -so males red belly is the sign stimulus
geese egg retrieval
-sight of displaced egg triggers retrieval behaviour
-this behaviour can be triggered by a vairiety of objects
-anything ‘egg like’ gooses will take to nest
Human Induced Rapid Environmental Change (HIREC)
habitat: change/loss/fragmentation
invasive/exotic species: predators, pathogens, competitiors
human harvesting/disturbance: eco-tourism, fisheries
pollution: noise, vsiual, chemical
climate change
HIREC ecological traps
turtles going into road
tree frog eating fairlylight because it looks like prey item; beetle
flies laying eggs on glass thinking its water
HIREC pests?
-lionfihs invasive in Atlantic Ocean
*impossibl to contain without natural predator
cane toads
introduced to australia, but eat everything
anything that eats them dies
toad flavoured sausage with nausea inducing chemical introduced to environment so animals eat them and develop aversion to toads
signal detection theory
ability to differentiate between important stimuli and random noise
individual heterogeneity
personality
undertand better if we compare animals to how humans feel
on a continuum
personality is related to
a. group living
b. dispersal and migration
c. reproducitve succes
d. response to environmental pertubation
e. risk of predation/parasitism
f. interspecific interactions
g. competition
h. habitat use
and so on (ubiquitous)
temperament
traits affect survival and evolution
behavioural syndromes
different traits of particular behaviours
water striders
-hyper-aggressive male try to mate with everything; male, female, split couples, dead insects they should be eating etc
-aggressive females: prey capture, web building, colony defence
-docile females; parental care
behavioural syndromes
-suites of correlated behaviours expressed either within a given behavioural context or between different contexts
-e.g. bold indivuals, more aggressive, solitary, active, show less parental care, live short lives and have low immunity
sociality
-to some, refers specifically to animals which form societies
-to others, everything is in some sense social
-in this instance, social animals are those that live in groups
-can call any group of animals, including humans, a swarm
social aggregations
-true social aggregations usually invlve social attraction
-animals in social aggregations must be able to communicate - need to be in sensory proximity
-not the same as resource-based aggregations
*where, if gven resource is clumped in space and time, animals that require that resource are as well
different social aggregations
-things occur on a continuum
-facultative sociality : associate socially when needed e.g. cheetahs, sometimes brothers work together even though they are typically solitary
-obligate sociality: associate socially throughout life
-many species move along this continuum at different stages of life
other social continuum
free entry : restricted entry
-decision on whether to accept new member to group
*may be due to relatedness etc
-starlings and sparrows
*in some cases, newcomers have to join at bottom of pecking order
hering
spend entire life in close proximity
if isolated, die
changers
- many species change their degree of sociality as they age, or across different seasons
-e.g. many fish highly social as juveniles, but become increasingly solitary with age
*also seen in crustaceans
-others, social as adult except in breeding season when sexes, typically, seggregate
locusts
-dramatic shift from being almost entirely solitary to being gregarious
-transition caused by tickling?
*hormonal cascade
*massive physiological changes
*brain size increases
*start producing pheromone
advantages of group living
-protection against predations
-increased foraginf efficiency
-reproductive success
-energy/resource conservation
finding food in groups
1.with more individuals, groups can search an area more efficiently
2. the group acts as an ‘information centre’ and comprises the collective info of group members
producers and scroungers
an example of game theory
should you go out to look for food, or let someone else do it?
sailfish
surround sardines
injure them by slashing group
sailfish groups mainatin high attack frequency
left/right handedness dependent on worn-ness of bill
co-operative foraging orcas
-biggest species of dolphin
-hint seals together
-seal makes raft to protect themselves from waves
-orcas push raft so seal is no longer protected
-orca blows bubbles to disorientate seal
cooperative hunting
ability to catch larger prey
hyenas, high catch rate but loose prey to bigger predators
army ants band together to break pupae of pupating insect
wild dogs
-optimum group size for catching largest prey
-1-2 individuals = fawn thompsons gazelle
-4 individuals = adult thompsons gazelle
-6 individuals can take down an adult wildebeest
antipredation benefits of group living
-mnay eyes hypothesis
-reduced encounter rate
*simple clumping of prey distribution
*selfish herd
-reduce predator success
*vigilance
*dilution effect
*confusion
*predator-predator interference
*mobbing, cooperative defence
selfish herd theory
each individual tries to reduce its own domain of danger
put another individual in the way to protect yourself
group structure
-different positions bring different pay-offs
-safest place is centre of group
*but central individuals get less food
-so if hungry, move to front to get food, if not, fall back to be protected
many eyes hypothesis
as group size increases, members can decrease their own vigilance without increasing risk of attack
-falcon can get 1 pigeon when by themselves, but as group size increase, can’t get close
predator confusion
-encountering large group of animals can cause sensory overload
-predator success rate drops as prey group size increases
-when encountering large group, predators appear to be indecisive, hesitation allows prey to escape
-only works if all prey look the same
costs of group living
competition
increased risk of parasitism and disease
increased opportunity of reproductive interference/suppression
conspicuousness
collective behaviours
-phenomena that result from social interactions among individuals
-governed by principle of self organisation
-behaviour of small components linked to functioning of dynamic group level properties
starling collective behaviours
-swarm for protection against predators
-individuals in group seem to act in unison
-turn togehter, move as one
-each agent adopts simple rules
-created by watching neighbour
ant trail following
-after finding food, ant migrates to nest leaving pheromones behind
-migrates betwee nest and food, each time building up more pheromone
-other ants pick up trail to food source
lane formation
-humans walking on same side they drive on
-ants pick a side to walk on and stick to it
-don’t bump into each other
zonal rules of interaction
-local focus: interact with a few near neighbours
1. zone of repiulsion (too close)
2. zone of orientation: move in same direction to stay with them
3. zone of attraction: too far away, so move closer (speed up to catch up)
zone sizes
-state and species dependant
-highily social species, more tolerant to high packing density
*sardines, herring, smaller zone of repulsion, largr zone of attraction
-hungry animal may enact large zone of repulsion and small (or no) zone of allignement
-fearful animals may enact a large zone of allignment and small zone of repulsion
examples of animals using zones
-individual animals respond to nearest neighbours
-wave of information spreads through group
-information speed typically > individuals
self-organised groups
-have to make collective decisions
bases of this :
a. interacting individuals
b. variation
c. amplification
d. positive and negative feedback
-more leaders, more individuals will follw what leaders do
*rely on decision of multiple individuals
quorum
only follow when a threshold number of leaders has been exceeded
leadership
-in caribou etc, experienced animals lead others through habitat
-don’t ‘shoot the leader’ as other individuals will become displaced
consensus building
timing & direction
if group spilts, all may lose benefits of group membership
increase in activity prior to move = active recruitment
swarm intelligence SI
- individuals independently acquire information
- info combined and processed through social interaction
- cognitive problem solved in way that cannot be implemented by isolated individuals
- wisdom of the crowd
-differential experience of individuals across groups
-animals at edge detect change and info spread through group
