post-midterms

- Annelid worms have bombs of fluorescent light that they use to distract predators and startle them for long enough to escape
- Bioluminescent sacs are homologous with other anatomical features of these annelid worms so this can help researchers figure out their derivation
Hymenopetra larvae secrete a deadly compound from their cuticle cavities when they encounter a predator

- Some mice have colouration that matches the beaches they live on
A single mutation of melanocortin is responsible for this

- They change colour quickly to avoid being seen by predators
Have sharp night vision and mostly change colours at night because that is when they are most preyed upon

- Noninsave light source that relied on red light to see nocturnal behaviour
- Found that they camouflaged in 71/83 times which could have been an underestimate as the camera may have missed them
- They could match their background through a form of crypsis in which they take on a singular skin colour that matches their background - rarer form of crypsis and mostly mimicked rocks around them
- The second kind of crypsis is more common (making up half of camouflage incidences) in which they make their skin splotchy which mimics their background
The third form of crypsis is the disruptive camouflage in which they take on large and dark strupes so it does not look like a cuttlefish

- Preyed on by bottlenose dolphins
- Dolphins follow their boat-whistling sound during breeding season
- Remage Healy and colleagues captured toadfish during the breeding season and they kept individual males in tanks, when the males began to boat-whistle to attract females they played one of three sounds: dolphin foraging pops, dolphin communication whistles, and shrimp snapping as a control sound
- Males reduced their calling due to pop sound by 50% and were unaffected by the other sounds
Males that were exposed to popping sound had higher cortisol levels than males exposed to shrimp sounds

- Obtained phylogenies of 6 parrot species
- Collected data on nesting behaviour and then mapped the phylogenies
- Predicted that competition that tree cavity nests is high so species prefer nesting in cavities and are favoured and predation is high on eggs during breeding so making tree nests is more favourable
- No evidence for increased clutch size in OC nesters
- Lack hypothesized an inverse correlation between nest predation rate and length of nesting period
- Brightsmith hypothesized that if the shift away from tree cavities was due to predation pressure then OC nesters should have longer nesting periods
- Data shows for amazonian and austrailian parrot species, those that nest in cavities other than tree cavities have longer nesting periods
- Amazonian parrots, estimates by Brightsmith include that almost all species that rely on cavities other than trees arose 20-30 million years
Nest predators ay have been responsible for the Amazonian parrots evolutionary shift away from tree cavity nesting as mammals were undergoing a large change at that time

- Co-evolution occurs when changes to traits in species 1 leads to changes in species 2 which in turn effect species 1
- Prey evolves behaviour that keeps itself safe, predator evolves greater detection abilities and so forth
Translocation introduces species to new areas to which they have no adapted

- Studied antipredator behaviour
- Rabbits are preyed on by foxes, cats, ferrets and other Australian natives like the qoll
Introduced rabbits to scent of forces, cats and ferrets and then found that rabbits reduced their use of the area but didn't react to scent of the quolls because they had not encountered them - but they are vulnerable now because they got moved to an area with quoll

- Front cortex of brain regulates effects of stressors on behaviours in humans rodents
- Smith and his team exposed mice to two different stressors, an odour of a predator or a physical stress
○ Then they were immobilized
Found that predator presence and immobilizer UMR increased the presence of acetylcholine, serotonin and dopamine in prefrontal cortex

- Most common prey response for safety
Can include running away or heading for cover

- Discovered that animals farther from a refuge began to flee sooner than animals closer to a refuge
- Animals involved in foraging, mating or fighting fled slower than animals that were not involved in such behaviours
- Predator size and speed also affects prey's perception of risk
○ Spines and shells reduced flight initiation distance
○ Armored animals were not as likely to flee vs animals without armoured
○ Ability to camouflage also plays a role and quality of habitat along with physical condition of prey
○ Other factors: age, size pregnancy, defending offpsring
- Experience and learning also play a role in whether they initiated flight
Greater the experience, the greater distance of fleeing

- Tend to flee predators en masse
- Marine sticklebacks encounter more predators and school more tightly than other sticklebacks
They also position themselves at a particular angle in reference to other schools

- Found that variation in schooling and variation in body armour of sticklebacks are linked to a region of chromosome 4
- Modified Eda gene in benthic fish and mated them to natural benthic fish and their genetically modified offspring schooled more like those from pelagic populations (who naturally have the Eda expression)
Eda gene explains stickleback schooling behaviour

- Attach their eggs to the vegetation that hangs over water
- Tadpoles drop down but have predators
- If predation is weak, eggs hatch in the later season which allows embryos to grow to a size that lowers fish predation
- Warkentin predicted treefrog eggs would hatch sooner if predation in the terrestrial environment increased because natural selection should favour embryos that can avoid predation
○ Less than 1/2 of the eggs she kept track of hatched
○ Eggs in clutches that were undisturbed hatched in 6 days
Snake predation and wasp predation either damaged the eggs or caused them to hatch earlier
When she released a snake into the cage, the vibrations of the snake resulted in eggs hatching earlier

If natural selection has shaped conditioned fear responses (meditated by the amydala) then this suite of behaviours should be heritable

- Gazelles are preyed on by lions, cheetahs, spotted hyenas and wild dogs
- Approach behaviour could possibly decrease current risk of predation, allow gazelles to gather info about a threat, serve to warn other group members of the potential danger associated with predators
- Fitzgibbon found evidence for decrease in risk of predation
- Cheetahs respond to the gazelle behaviour when gazelles are in large groups which could cause cheetahs to leave an area sooner than normal leading to rates of decreased mortality
- Costenefit
Gazelles spent 4% of waking hours involved in approach behaviour which could be used for other things like foraging

- Beetle on a branch and predator approaches, they can either fly away or feign death but not both
- For behavioural assay of feigning death
○ Dropped beetle through hole into cube shaped apparatus that had a grip on its bottom and tested whether th ebeetle dropped straight down (poor flyer) or whether it flew as it was falling and how far it flew
- Two genetic lines were established in a death-feigning treatment - in the "long duration" line the seven males and seven females who displayed the longest duration of death feigning were selected and allowed to breed with another
- In the "short duration line" the 7 males and 7 females with the shortest duration of death feigning bred with one another
- Eight generations of artificial selectin on death feigning produced dramatic differences between selected lines
- Individuals in the long duration line showed death feigning times that were about 40x as long as those in the short duration
Negative genetic correlation between death feigning and flying abilities

- Created lines with best fliers and worst fliers
- Same negative correlation was found
- After 8 generations of the best fliers, displayed very short death feigning times
- Beetles in WF line displayed long death feigning times

Beetles in populations selected for long bouts of death feigning had higher brain concentrations of dopamine than beetles from populations selected for short bouts of death feigning
Sometimes prey signal the dangers of encounters to predators - like tiger moths producing warning sounds to bats so bats can avoid them because this sound signals a noxious taste

- In caterpillar stage, monarch butterflies ingest milkweed which makes them resistance to infection but can be dangerous to birds
- Chemicals (cardiac glycosides) in milkweed are stored in butterfly tissue
- If a bird eats this butterfly, it can become very sick
- Colour patterns on the monarch butterfly indicate to bird that it will get sick
Even touching the monarch may be good enough for the bird to realize it will get sick

- Individuals flag their tails when they see a predator
- Occurs when predator is safe distance from potential prey
Flagging warns kin/nonkin about predatos, tightens group cohesion and benefits, signals to predator it has been seen and shouls stop, causes other group members to engage in antipredator activities, and serves as a sign for appeasing dominant group members

- White tailed deer that run fast flag their tails and communicate to predator that an attack is unlikely to succeed
Ungulates also snort to indicate health and vigor to predators

- Bombardier beetles use chemical weapons
○ Blast predators with a highly noxious spray
Beetle can discharge acidic spray 20x before depleting its supply

- 2 compartments
- Large compartment is reservoir and it has hydroquanines and hydrogen peroxide
- Small compartment is reaction compartment which has catalases and perxidases,
- When beetles are threatened, they mix contents of both compartments and release it (p-benzoquinones)
- Release causes audbile pop at 100 C
Propsed to have evolved from Metrius contractus who had same compartments

- Produces froth secretion when attacking rear area
- Forces secretion forward when attacked by front
Discharge lowers chemicals from 100 deg to 55 deg C

Once they spot danger, they fly toward it and aggressively chase it away

- Had a model and naïve bird each in its own aviary and each could see a noisy friarbird (they have never encountered friarbirds before)
- Next to friarbird the model saw little owls, a known predator
- From naïve birds viewpoint, the model seemed to be attacking the friarbird when it was attacking the owl
- The naïve birds became much more likely to attack the friarbird
Chain of information across birds can be passed along until broke - about friarbird being dangerous

- Alter foraging choice based on predation pressure from redtailed hawks
- Squirrels that could carry their food items where they found them or carry the food to cover were more likely to carry items to a safe cover, particularly as the distance to safe cover decreased
- The closer the refuge, the more likely the squirrels would use it
When it was a quick run to home, they'd often make that run

- Presented squirrel with cookie (longer handling time) or a small cookie (smaller handling time)
- Combo of large and small chunks were placed either close to an area of cover or farther from safety
- Profitability of small food items is greater than profitability of large food items
In absence of predation, it was predicted that squirrels would take small food, and total handling time associated with larger food items was great enough that optimal foraging models predicted that larger items should be brought to cover, particularly when the distance to cover was not great (not the case for smaller items)

Anthropomorphism – the
attribution of human traits
to non-human animals
- Most early reports on imitation in non-
human species were incorrect

An observer learns a new behaviour
by watching a demonstrator
• (Neither the presence of a
demonstrator nor some outcome of
the behaviour are sufficient (e.g.
odour, open cones, wounded prey)

The majority of animals just do not do it
• We can easily do it
• How does the observer’s motor system
‘know’ which muscle activation will lead
to the observed model’s movement?
• Mirror neurons in the pre-motor cortex
are active both when an obser

Critical data indicating that an observer
learns a new behaviour by watching a
demonstrator exist for very few species
• Local enhancement is prevalent &
almost certainly explains milk bottle
opening in blue tits

5 observers watched a demonstrator
pushing the screen to the left with its
beak to gain access to food
• 5 observers watched a demonstrator
pushing the screen to the right with its
beak to gain access to food
10
11
12

5 observers watched the screen move
to the left in the presence of a (non-
pushing) demonstrator who then had
access to food
• 5 observers watched the screen move
to the right in the presence of a (non-
pushing) demonstrator who then had
access to food
Hidden experimenter operating the screen
Predictions
• Focals that see demonstrators moving
the screen would move the screen in
the same direction as the demonstrators
• Focals that see the screen move would
either not move it or move it at either
direction

Focals that see demonstrators moving
the screen would move the screen in
the same direction as the demonstrators
• Focals that see the screen move would
either not move it or move it at either
direction

higher mean screen pushes by matched ones in imitation
higher mean screen pushes by nonmatched ones in control treatment

Task: open a Plexiglas box to get fruit
• Demonstration: half the subjects
observed a demonstrator poking 2
plastic rods & then lifting the lid
• The other half observed the
demonstrator twisting clockwise and
pulling the plastic rods & then lifting the
lid

• To control for non-imitative alternatives
– local enhancement – the observers
play with the box because the
demonstrator does so
• Prediction: observers would employ the
technique they have observed to open
the box
25
26
27

Chimps approach
termite mounds with
proper tools:
• The first stick is thick
to break into a tunnel
• The second stick is
thin, with a “brush tip”
to extract termites
• The set is unique to
that group
Experiment with 3 groups each exposed
to pan-pipe

Control: no expert present
• Poke: expert trained on the poke method
• Lift: expert trained on the lift method
(expert was a high-ranking adult female)

For 7 days, only the expert was allowed
to operate the pan-pipe
• Other group members closely observed
the expert
• Then all group members had access to
the pan-pipe

• The six control chimps failed to gain food
• 15/16 chimps in each of the expert
groups gained food within one minute
• Almost no adoption of the lift technique in
the poke group vs. mixed adoption of
techniques in the lift group
- found that a considerable portion used poke and after a 2 month break, almost all individuals used poke

Very limited culture in other great apes
(chimpanzees & orangutans)
• No known culture in other species
• Other species may have one tradition
(e.g. distinct songs in song birds)

Chimps use only simple tools. Ancient
humans used complex tools (e.g. traps
made of complementary parts)
• Ancient humans used weapons for
hunting
• Humans have developed complex
cumulative culture, which relies on
language & technology

Birds and mammals have the highest body weight and brain weight correlation??
There is a positive linear association
between brain and body weights (on a
log-log scale)
• The intercept varies among classes
Y = a X ^b
log(Y) = log(a) + b log(X)

- Opossums have a smaller brain size for animals that are 1 kilo in weight, falls below average (regression line)
- Same with blue whale
- Apes are above average
Biggest exception is modern human, very large brain for body

Within mammals, humans have a larger
brain size than expected for their body
size (= large positive residual)

Innovation – novel solutions to
environmental or social problems.
Examples: use of a club to attack a
snake; use of tin cans to make noisy
dominance display

Social learning

Executive brain (neocortex + striatum)
the brain structures involved in social
learning and innovation

Relative volume of brain region = ratio of
the brain region to either another part of
the brain or whole body
Executive brain ratio = Executive brain /
brain stem
Some primate data suggested a positive
correlation between innovation / social
learning and brain size
New studies with much greater power
indicate no association between social
learning / group size and brain size

Sweet - simple carbs (brain runs on simple carbs)
Bitter - possibly poisonous or spoiled food
Salty - Sodium (Na) is an essential nutrient
Sour - ripeness of food

Single origin in
vertebrates
• Some dislike it, some
like it
• Adaptive significance
unknown

Umami – the taste of free glutamate, a
common amino acid indicating the
presence of protein
• Glutamate rich foods: meat, fish, milk,
some vegetables (e.g. tomatoes), some
mushrooms and algae
Glutamate rich foods serve as natural
taste enhancers (cheese, tomato sauce)
• Monosodium glutamate (MSG) is an
artificial taste enhancer

It forages close to shelter because of
predators (eagles)
• It spends much of its time feeding and
storing food for the winter
• The food is low in calories and contains
poisonous plant compounds
- Send warning calls to tell others that patch is taken
- Eat all parts of plant
- Prey to eagles
- Stacks food in special ladder that will last it during winter when food is minimal
- Pica collects poisonous plants because the poison works as a preservative
- Make several trips a day to store food

• Energy content
• Nutritional content
• Cost

The majority of modern people face the
novel problem of higher energy intake
than energy expenditure

Animals are adapted to maximize
consumption of food rich in energy and
specific nutrients, which are typically in
short supply (fat, protein,
carbohydrates, salt)
• Animals are also adapted to minimize
energy expenditure and exposure to
danger (predators, injuries, dehydration,
hypothermia etc.).

Animals typically attempt to maximize
food consumption while minimizing
energy expenditure
– Food is limited
– Foraging exposes foragers to danger

Many of the nutrients that were in short
supply over evolutionary time are now
abundant and relatively cheap
• The majority of people can live
nowadays with minimal energy
expenditure

- 1500% increase in vegetable oil over past 110 years
- 25% increase in human energy consumption over past 50 years
- 30 min reduction in daily physical activity
- 25% decline in metabolic MET which is the ratio of physical activity in metabolic rate over resting metabolic rate
- inadequate deit or exercise caused 63% of premature deaths in canada

Obese people had more covid hospitalizations

Maintaining energy balance
• Cardiovascular health
• Physical and mental health (lower rates
of some cancers, depression, anxiety)
• Increased neurogenesis & survival of
new neurons
• Enhanced cognitive performan

Cardiovascular health – improved blood
flow to the brain
• No micro-strokes
• Increased neural survival & growth, and
synaptic plasticity
• Anti-inflammatory effects
• Lower rates of neurodegenerative
diseases (e.g. Alzheimer's)
Effects of exercise:
• In rodents, exercise more than doubles
the production of new neurons in the
young and aged brain
• In humans, exercise increases new
blood vessel formation, cerebral blood
flow and cognitive function

In rodents, exercise more than doubles
the production of new neurons in the
young and aged brain
• In humans, exercise increases new
blood vessel formation, cerebral blood
flow and cognitive function

An evolutionary analysis of animal
feeding behaviour helps us understand
a major modern human dilemma
associated with disease and premature
death

Animals must maintain short-term and
long-term fat reserves
• Fat reserves have benefits and costs
• Benefits: insurance, insulation
• Costs: weight: increased energy
expenditure, reduced mobility 
increased predation risk

10-20% in men 
• ~ 10.5 kg (~95,000 cal) for a 70 kg man
• 15-25% in women 
• ~ 12 kg (~110,000) for a 60 kg woman
• Sufficient energy for over 50 days!
Fat has other key roles
• >60% of the brain
• In all cell membranes
- Myelin is 35% fat
Animals show adaptive fat storage
• Winter in higher latitudes: longer nights,
lower temperature, higher variance &
uncertainty

- Control received food throughout
- Then food was removed for each group for either breakfast, afternoon or breakfast or afternoon
Not having food in afternoon led to higher amounts of fat storage

Focus on:
• Encounter rate (# of items encountered
per unit time)
• Energy content (calories)
• handling time (time from capture to
complete ingestion)
• (We will discuss Predation risk later

If the encounter rate with the most
profitable prey (prey 1) is above a
threshold level, only this prey should be
eaten
• The encounter rate with prey 2 should
not affect the decision whether to feed
on prey 2

- Model predicted low density
Great tits were supposed to ignore prey 2
At low prey densities, both types should
be eaten
• At high prey densities, even when the
large prey is less common than the
small prey (0.3:0.7), only the large prey
should be eaten

The results mostly agreed with the
predictions, but the great tits took a
small proportion of small prey even
when the model predicted that they
should not.
• The latter is a typical result in such
experiments.

The problem: even a good patch may
be depleted quickly, meaning that there
is a negative correlation between patch
residency and the rate of food intake

It’s 3 times more common than prey 1,
but only half as profitable as prey 1
- Sometimes it makes sense to bypass prey 2 and only focus on prey 1
- If encounter rate is high, it makes sense for bear to eat brain and eggs of fish
We can assume that the encounter rate of brain and body is the same so the bear can ignore the fish body

R=E(T)/(tau + T) - The gradient of T is maximzed when it is tangent to the nergy gain curve

A forager should stay in the current
patch until its rate of intake is equal to
the average rate of intake in other
patches

Energy rich, sodium poor terresentrial plants and sodium rich energy poor aquatic plants

Balancing (i) energy-rich, sodium-poor
terrestrial plants and (ii) sodium-rich,
energy-poor aquatic plants
• A simple model is insufficient
• We require a model that allows for the
maximization of the rate of energy
intake while meeting the required rate of
sodium intake

Such a model predicts that moose
should spend ~18% of its foraging time
on the sodium-rich, energy-poor aquatic
plants, approximately what moose do

- Male bowerbirds adorn their nests to attract mates
- It is hypothesized that male great bowerbirds use optical illusions as the males arrange things like shells, bones and stone in the "gesso" area and females watch them
- The optical illusion makes the trinkets seem larger than they are
Increases mating opportunities for males - if researchers move objects around, they move them back

- Intrasexual selection: When members of sex compete with each other for access to the other sex
Intersexual selection: Individuals of one sex choose which individuals of the other sex to take as mates

- Females produce fewer but larger gametes so each egg is valuable because of its size and scarcity
Sperm takes less effort to produce and are found in larger quantities

- Females should be choosier about sex because eggs are more expensive to produce, and female's reproductive success is limited
- Females greater choosiness in mate selection should translate to greater variance in the reproductive success of males

- In cichlid fish ( A burtoni gravid) - the females select between males and prefer, more dominant and aggressive males as mates
- Wanted to see if fighting between males triggers actions in certain areas of a female's brain
- Female was placed in an aquarium with two males on each end (males were paired by dominance and size rank)
- If a male was moved from side to another, he was likely to lose because males are territorial, so females saw the preferred male either win or lose
- Measured c-fos and egr-1 gene expression in females
Found that when preferred male wins, gene expressions increase in areas linked to reproductive success and when preferred male loses, gene expression increases in areas linked to anxiety-like behaviour which could reduce mating and reproduction

Traits such as plumage, bright colours and courtship displays

- Interval between pulses impacts females choice of mates
Genes and loci of genes impact the variance in courtship songs

Sexual selection tends to be stronger in polygamous and polyandrous systems because they have lots of mating opportunies or not many

Human disturbances can impact female mate choice

- Pollution due to human activity
- Pollution in Lake Victoria causes Cichlid fish to mate with other species of fish because they cannot determine which fish is a Cichlid by the colouring of their skin
Causes hybridization of cichlid fish with other specie

When closely related endangered species live together, individuals may imprint on adults from the wrong species which could lead to maladaptive behaviour

Females may become more vigilant to human behaviour and disturbances rather than spending time mating

- When male number in a population is low, females mate with males that they'd never normally mate with
- Rippling effect to next generation
- Females may invest fewer resources in their offspring than they do when they mate with high quality males
Offspring may be less healthy

- The direct benefits model of mate choice hypothesizes that selection favours females that have a genetic predisposition to prefer mates that provide them with tangible resources
Females that choose males that provide them with important resources like food and shelter will do better than females who are less choosy

- Female scorpionflies choose their mate based on the size of the prey they bring to them (nuptial gifts) - consumed during courtship
- No gift = will be met with rejection
- Females also look at how long they'll mate with the male based on the size of the gift and how much of a benefit they'll get from that gift
- When the gift is between 3-19 mm, there is a positive relationship between prey size and copulation time - the female pulls her abdominal tip away from the male to end copulation
- A copulation time of less than 7 minutes often involves no sperm transform
- A female that chooses a male that brings her a large gift produces more eggs and lives longer
- Males often sample and discard prey that are too small for long copulation times
- Males also steal prey from other males by mimicking the behaviour of females and then stealing the prey

- Good gene models propose that selection favours that females choose the males with genes best suited to their particular environment
- for example, genes associated with superior foraging skills or the ability to fend off predators. In doing so, the females receive indirect benefits, in the sense that their offspring receive some of the good genes that led their mother to choose a particular male as a mate in the first place
- . Good genes models are sometimes called “indirect benefit models” of sexual selection.
- Males do not coerce females, female pronghorns travel long and spend a lot of energy by visiting males that have a harem of females
- Predicted that females looked to see how well males are protecting their harem so a larger harem would mean greater reproductive success for the male
Found that offspring from attractive males had higher survival rates

- The costlier a trait, the harder it is to fake
- Females choose males with strong resistance to parasites, which is had to fake
- Endoparasites are parasites that live in their hosts and can't be seen
- Females can see if males are parasite resistant by using another trait T
○ If males possessing trait T also means tat males are good at fighting endoparasites, then females use it a proxy
- Healthy males tend to be more colourful than parasitized males

- Proteins produced by the MHC genes gyide the body in identifying self versus foreign body cells
Biologists predict that animals prefer mating with those that have a dissimilar MHC to have offspring with stronger immune systems

- Men were told to wear a cotton shirt for 2 nights, and blood samples for males and females were taken and females were given T shirts for males with either similar or dissimilar MHCs
- Women not on oral contraceptives found the smells of the dissimilar shirts more attractive
Females may also use perfume that enhance their own MHC scent

- Sticklebacks in interconnected lakes have varying MHC profiles, ranging from a difference of 2-8 alleles
Females always preferred male with greater difference

- Exposed females to two different water columns - one that had male swimming in it and another had a male + supplied MHC ligands
- Found that when a pair had a less than optimal # of MHC, the synthetic ligand water was more attractive
If pair had optimal #, other water column was more attractive

- Female sticklebacks tend to begin foraging after giving birth and eat the eggs of other sticklebacks
- Predicted that females would be repelled by male MHC peptide that she was attracted to prior to mating because that would reduce the chance she eats her own eggs
Found evidence for this to be true

- Models of runaway sexual selection center on the relationship between alleles and two loci - one locus houses alleles that code for female preference and the other houses alleles associated with the male trait that females prefer and over time
- Specific genes from both alleles become associated with each other over time
- Group of females with some who prefer colourful males and some who have no preference, and some males are brighter than others so we can assume that the male colour and female preference are in both in females and males but exhibited in the appropriate sex
○ Females that mate with colourful males should not only produce colourful sons but also daughters possess their mothers genetically coded preference for colourful males
- Over time the allele in females that codes for colour preference and the male's brightness allele should become linked so that if the frequency of one changes, so does the other one

- Females prefer to mate with males that have long stalk eyes
- One treatment had long stalk eyed males mate the other had the shortest and female mating was random
- The treatment where the long stalk eye length cased average male eye length to increase (exaggerated)
- Conversely, in the other treatment, the eye length decreased
However there was no significance found between selection on males in long eye stalk treatment producing significant changes for females prefer long eye stalks

- Sensory Bias models posit that when a male trait first emerges it is a preferred by females because it elicits a neurobiological response that is already in place in females and the response is not associated with mating preferences
- Suppose red berries are the best food source available, females that are best able to search out and subsequently eat red berries survive and reproduce better so natural selection should favour the neurobiological circuitry I females that allows them best to hone in on red items in their environment and then red feather should arise in males
Female trait should always predate male trait in phylogenetic model

- Males in two closely related species of frogs use calls to attract females (pustulosuis and coloradorum) - a whine
- Females pick up on the whine with the basilar papilla in their ears
- Pustulosus but not coloradorum add a chuck to their call, and female pustulosus prefer to mate with the chuckers
- Females have amphibian papilla that is sensitive to low frequency sounds and it is hypothesized that they already have a preference for low frequencies
Common ancestors of both frogs did not chuck, but the chuck appears females prefer to mate with them

- Young individuals imprint on the behaviour and morphology of adults - almost always their parents and use these characteristics to guide their subsequent of mates
Imprinting is restricted to some small time window during normal development but this varies among animals

- Attached red feather to adults heads and suspected that the chicks would develop a sexual preference for red feather heads
- Control group had no red feathers, one had both parents with red feather and third and fourth group had either only father or only mother with red feather
Females with red feather fathers and males with red feather mothers preferred feathers on their mates

- When a male zebra finch is kept in isolation for 2 months, he often imprints on the first female he sees after isolation
Found decreased spine density in on earea of zebra finch brain after exposure to female

- Will stay in areas where they can mate with a female
- Tested hypothesis that classical conditioning at adult stage might override effects of sexual imprinting as a juvenile
- Three trials: One with male with brown strain,female with brown strain adult female from blond strain
- Showed male blond strain and they could mate, and then showed female from brown strain but could not mate
Males spent more time around blond female because they conditioned blond females with a mating opportunity

- When a male's probability of being preferred as a mate increases as the result of being preferred by a female I the pas
- If a male has an X percent chance of mating if he has not recently mated, and a Y percent chance if he has recently mated, the effect of mate-choice copying is defined as the difference between Y and X. Mate-choice copying occurs if Y − X > 0; the greater Y − X, the stronger the effect of mate-choice copying.

- Mating arenas are called leks
- Males strut with tail spread out, flap wings and hiss
- Females visit males in groups and sync their visits
- Found that males who mated were likely to mate again and fairly quickly
Suggests that mate choice copying occurs quickly in females

- Placed dummy females within a lek for males before actual females arrived
- Males courted these females and attempted to mate with them
- Females were more interested in these males that had tried to copulate (even if it was just with models)
Suggested mate choice copying

- Hypothesized that mate choice copying behavior would increase as more females mated that day (unanimity)
Hypothesis turned out to be true as mate choice copying increased as more females arrived in a lek

- Oxytocin plays a role in mate choice, social behavior, maternal bonds and individual recognition
- Females were asked to choose between a male that was with an estrous female or a males that had been with a non estrous one
- Females preferred the one that had been with an estrous female and other females copied their choices
- Females that had the OT knocked out did not copy the other mates choices
Knocking out the gene for oxytocin has the special effect of inhibiting mate choice copying behavior in mice

- Learn songs from "tutors"
- Collected juvenile + adults birds from South Dakota and one population from Indiana and cross fostered them
- Raised juvenile south dakota birds with either south dakota parents or indiana parents,
SD juveniles preferred mates of the population their parents came from indicating cultural transmission

- They form harems during mating season and fight off other males to defend their harems
- Hypothesized that males should use honest signs to indicate their fighting abilities since it takes up a lot energy
- Hypothesized that main indicator for fighting was roaring
- Roaring was associated with parallel walking
- Harem holders roar more than those without a harem
- Roaring increased when a harem holder was being threatened
- The more a male roars, the more likely he is to fight
- Roaring contests were more common between mature stags of equal fighting ability than between stags of unequal fighting ability and roaring rarely escalated during parallel walking

Researchers played tapes for red deer males of other males roaring at different rates and measured responses, they found that when playing roars from a larger opponent, the male red deer were more attentive and increased their own rate of raring

- Heavier males succeed in interrupting copulation between lighter males and females
Hypothesized that females incite the violence

- Up to 40 females are defended by a single dominant bull seal and there is variation in male reproductive success
- Females protested some mounts by calling or moving out of the way
- Led to highest ranking males mounting females that rejected subordinate
Competition is caused by females so she can get the highest ranking

- Hypothesized that there is greater sexual dimorphism in the species with the greater harems
- Found positive correlation between harem size and dimorphism
The more females, the larger the relative size of males

- Parental males are light bodied with dark yellow breasts and build and defend nests
- Takes 6-13 days for their eggs to hatch
- Sneaker males are small and swim quickly into territories and shed their sperm and swim away
○ Competition between sneakers to fertilize eggs
- Satellite males look like females and positions himself between a spawning pair and fools parental male, but then releases its own sperm into female
- High density of sperm per ejaculate should be preferred in sneaker males
- Sperm for parental males was more likely to fertilize eggs rather than sneaker males
- Males can adjust the number of sperm they release based on female or male-male competition
Sometimes male release a spermatophore - a capsule of sperms with proteins to pick up in the ovipore

- Females pick up only one when males deposit it
Females receive indirect benefit

- Treatment 1: lone male, treatment 2: two spermatophore producing males, treatment 3: male placed with one that does not produce
- Treatment 1 produced the most, in presence of other males, they reduce spermatophore
- Males trade off quantity versus attractiveness of spermatphore production
- Females would prefer a patch of an equal number of spermatophores from treatment 2 than treatment 1
Mediated by olfactory cues

Hunting of vervet monkeys of all sizes in East Africa
• Predator-prey arms race: monkeys stay away from
exposed tree tops  eagles fly among trees 
monkeys have a special eagle alarm call and attempt
to drop to dense bushes...
• Parental care: 4 months in the nest, 9 months to
independence
Balancing feeding and
antipredatory behaviour

- Can kill prey 4x their own weight

- Flies have good hearing and draw blood from forgs

Ants could choose between two patches
containing liquid ant diet of different
concentrations
• The high concentration patch was either
safe or had a predator
- Predators were satisfied after 24 hrs so less active

Ants preferred the safer, less rewarding
patch as long as:
• it was not much worse (as low as ~ 8
times worse, or 12%), and
• the predator remained active (4 vs 24 h:
predator’s attack rate declined over time)

True , and starlings with diets had higher ascent angles. Starlings with higher weight took a longer time to ascend and when they were protected by cover they gained weight (cover protected from predatours) .

When hawks were absent, they had higher mass and then as they increased they lost weight over the years

birds vary their fat reserves depending
on expected benefits and costs:
• More fat when food is less certain
• Less fat when predation risk is higher

Rapid response to the snake attack
• Embryos rely on vibration cues
• Frequency, duration and spacing of
vibration events
Eggs escape by dropping into water

The eggs are laid on leaves above the
water
• Hatched tadpoles drop to the water
• The leaves are associated with
terrestrial predators (snakes and
wasps), the water has aquatic predators
(shrimp and fish)
- Strongly prefer to hatch at night because of predation

Peak hatching of undisturbed eggs is at
7 days
• Early hatching is associated with higher
predation on the tadpoles in the water

Experiment: let experimental treatments
of eggs to be attacked by snakes at the
ages of 5 or 6 days and monitor
hatching

Less eye-catching than predation, but a
major cause of mortality in all animals
including humans
• For historic reasons, we term tiny
parasites such as bacteria and viruses
disease

37 million people in the world have
AIDS, 2.1 million are infected annually,
1.1 million died in 2015
• More than 35 million people have died of
AIDS since 1981
• ~2 million people, mostly children die from
malaria each year
• Flu kills about 30,000 people a year in the
USA
• SARS, avian flu, COVID-19

Malaria may have killed half of all the people
that ever lived
• More people are now infected than at any
point in history
• Up to half a billion cases & 2 million deaths
every year, half of those are children in sub-
Saharan Africa

Snails are intermediate hosts
of a trematode parasite
(Protozoa)

Experiment comparing egg laying in sites
with:
• No snails
• Low and high parasite infections rates
• Low and high snail densities

Infected areas had less eggs ad uninfected areas had more (esp with low density measured in eggs/pond bc the more eggs, the less space you have so you'd hatch less)

- Live in streams and a single group resides in a pool and there is dominance competition within these groups in which the fish at the top get their first preferences for food
- Hypothesized that this would result in slower growth rate for less dominant fish and they may leave the pool for another one
Found that when subordinates left, the amount of food in the pools was still approximately equal, however the growth rate of the subordinates was significantly higher because fish tend to move to areas with less competitors

- Occurs when an animal sends threatening signals or engage in physical combat
- Predator prey interacts are generally not considered to be aggressive
- When aggression occurs in group-living species and individuals interact with each other many times we can measure dominance hierarchies which are rank orderings of the individuals based on the results of pairwise aggressive interactions in such groups
Individuals at the tops of hierarchies generally have access to more food, mating opportunities and safer territories

Huxley's view on aggression
- The strongest animal will always win and aggression will lead to a bloodbath

Kropotkin's view on aggression
Animals interact in mutually beneficial and cooperative ways more than they do aggressively

- Surge in adrenaline and norepinephrine produces a quick increase in blood sugar which is delivered strategically to the brain, heart and skeletal muscles
- The digestive and reproductive systems are shut down temporarily
- From an ultimate perspective, the decision to flee or fight is based on the costs and benefits of aggression
○ When it is beneficial to be fight and be aggressive, that is what will be favoured
- From a proximate perspective, we ask questions about immediate causation and aggression
○ Focusing on hormonal responses
○ For example, dominant individuals display increased androgen levels - like testosterone and they are more likely to fight than flee and fight winners have more circulating androgens
○ Subordinates tend to have higher levels of glucocorticoids circulating than androgens
○ Dominants can also have high glucocorticoid levels when challenged by subordinates
○ If fighting is costly, it is better to display subordination

- Colour can indicate individual's rank which indicates whether it will engage in aggressive behaviour or not
Done by fish as they have control over their pigment

- Males go through circling, charging, biting
- Subordinates swim closer to surface to avoid future aggressive encounters
- Dominant individuals develop dark vertical eye bands and subordinates develop darker body colours
- Swordtails: Dominant males display red lateral stripe and black if they are subordinates
Androgens and glucocorticoids aren't the end all be alls with aggression - there can be many more chemicals and other things

- Low serotonin levels are often linked with high levels of aggression but lower social status in mammals
- In fish, subordinate individuals have increased serotonin levels leading to reduced fighting behaviour
- In crustaceans, increases serotonin leads to enhanced aggression and higher social status
- Loser crustaceans can be made more aggressive if given serotonin after losing a fight (proven after injecting fluoxetine (serotonin inhibitor) in lobster)

- Breeding programs can introduce new selection pressures on animals by radically changing the environment from one that animals would experiencing in the wild
- Kelley and her colleagues designed an experiment to examine whether breeding programs change the level of aggression in animals compared those found in natural populations and how
- Compared aggression between natural endangered butterfly split fin fish and those captively bred in a London zoo
- Aggressive behaviours in males of both populations were similar except captive populations displayed territoriality that was not seen in natural populations
- Captive bred males showed much higher levels of aggression than males from the natural population - especially in high density populations which was surprising because structued environments typically reduce aggression
Likely that genetic changes increase aggression

- Territories are not in a fixed place for speckled wood butterflies
- A male has a territory that is an open patch dilineated by well lit areas that amerge when the breaks through the cloouds
- When a male is an well lit patch, he secures a mating advantage over others
- Physical combats can take place for access to territory and is usually settled with the resident winning and intruder retreating
- Little aggression because it is a prolonged fight over a short lived source of a sun patch which is not worth it
- Once a male finds out territory is occupied, he leaves
- A butterfly needs to be an owner for a few seconds for this rule to successed

- Male M1 was experimentally made territory owner and always defeated intruder M2
- But when M1 was removed for even a short amount of time, M1 would then defer to M2
Contests only escalated when both males acted as an owner when they both arrive to sun patch at the same time but do not notice the other one - fights occur at this time

- Individuals can choose to display aggressively for any duration of time, the more a behaviour is displayed the more costly it is, and there are no clear cuses such as size, territory possession and so forth that contests can use to settle a contest
- V = Value of resource
- The probability that a contest lasts x units of time is equal to (2/V)e^-2x/v
- Predicts that animals will choose randomly from a specific exponential distribution of lengths defined y the probability function above
Predicts that all contest lengths from this ESS function lead to equal fitness gains to individuals

- Females arrive at dung patches to lay eggs and males aggregate at such patches for access to females and males compete with each other
- How long should a male stay at a given patch?
○ If he stays too long, he will encounter fewer and fewer females and if he leaves too quickly, he will miss mating opportunities
Stay times were found to be equally distributed - approximately 4 mins and when this time is consistent, stay times result in equal fitness for all males

- Analyzes fights between individuals that involve assessing opponents abilities in bouts
- Individuals assess their opponent's fighting abilities (statistical sampling)
- A single sample is a single assessment of a fighting ability and introduces a single random variable
- The more sampling, the lower the error rate is, so the individual can be more confident in whatever is being assessed
- Eventually one individual will be found to have very low odds of winning a fight
- The sequential assessment game examines contests in which the level of aggression varies from relatively mild to very dangerous
- Individuals should ideally begin with the least dangerous tyupe of aggressive behaviour and probe/sample each other and once all the information about the opponent's behaviour is exhausted, the next dangerous type of aggressive behaviour should be used until saturation and then so on until chances of winning a fight are gauged
- Model is not fully supported

- Aggressive male hierarchy displays range from colour change to tail beating, biting while biting
- Male fish were arranged pairwise and supported the sequential assessment model
- Fish assessed weight asymmetries as heavier fish are more likely to win
- When numerous behaviours are used in an aggressive contest, they should approximately be in the same order across all fights
- Shorter contests should have fewer types of a behaviour
Males begin with a weight assessment, and then tail beating, biting, mouth wrestling and then circling

- If animal 1 has recently defeated animal 2, it may be more aggressive in it next interaction and animal 2 may be less
- Animal 3 seeing animal 2 lose can become more aggressive with animal 2

- Aggressive interactions causing an animal to win can cause it to win again (Winner effect)
- Losing an aggressive interaction can cause an animal to lose again (loser effect)
- Winner and loser effects are defined as an increased probability of winning at time T and then based on victories at time T-1, T-2 and so on
Loser effects are more common than winner effects and are associated with more circulation of glucocorticoids and lower testosterone than winners

- Trial arena had female in the center and one male at each end
- The two males had not been involved in any other aggressive interactions for 6-12 months before this and were pitted against each other and in all pairs one male was at least 10% larger
- 10 winners and 10 losers were chosen from each contest and were matched against a same sized male copperhead that had no prior experience
- Prior winners were not more likely to win again nor were they more likely to win than their opponents that had no experience so there was no winner effect
- Loser effect was found - the losers were more likely to lose again and again and cede access to females to other males
- Two time losers lost all contests with smaller opportunities

- Assessed winner and loser effects in aggressive interactions but also in aggressive interactions from two moves back in time
- W (winner) L (loser) N(neutral - no wins or losses)
- Compared fish in WW versus LW and LL vs WL treatments - previous moves (penultimate - next to last) were found to predict probability for winning or losing
- Fish experiencing WW were significantly more likely to win than fish experiencing LW
- Wins and losses two moves back had less of an effect on current outcome than wins and losses one move back in time

- Can impact hierarchy formation
- In green swordfish, males have linear dominance hierarchies and bystanders first observed aggressive interactions and were then paired with one of the individuals they observed
- In one treatment, the bystander could observe the fish through a one way mirror and in another treatment, the bystander could not see the pair because of an opaque partition (control)
- With the opaque partition fish, the winning and losing was determined through the winner or loser effects
- With the one way partition. Bystander effect, and winner and loser effects could affect contests between the winners, losers and bystanders - bystanders were more likely to avoid the winner at all costs and they did not initiate aggressive behaviour however they won against losers that persisted or losers that escalated aggressive actions and this was not the case for the opaque partiton fish
- Bystanders responded similarly to losers regardless of whether they observed the winner win or not

- Testosterone levels rise in bystanders when watching other males fight
Testosterone may prepare bystander for future aggressive interactions by indirectly affecting attention, learning and memory (can be helpful if attacker attacks it or anyone in vicnity)

ndividuals in fights have behaviour affected by bystanders presence

- Chimps scream during pairwise interactions and winning and losing screams are different
- Victim screams work to entice support from observers to possibly break up a fight
- Looking at screams of mildly aggressive interactions, there was no difference found in when an audience was present or absent
- With severe aggression interactions, victim screams were longer and more intense with an audience present - but this was only seen if an audience member held a rank in the hierarchy that was equal to or above the rank of the aggressor
Was successful in the sense that screamers often did get the intervention they wanted

All the theories: winner, loser, bystander effects, audience effects suggest that groip living animals are embedded in complex social networks

- Some males break up fights between other males
- Experiment was done in which policing individuals were removed to see effects of removal
- Aggressive behaviours became more important as policing individuals were removed
- There were fewer play and fewer grooming partners
- Reach - a term to describe how quickly info can spread within a group was decreased in terms of play and grooming behaviour which reduced the spread of pro social behaviours
Removal of policers also led to formation of smaller subgroups whose members only interacted with each other

Females raise young and hunt
• Hunting is dangerous
• Males eat, have sex and protect their
female mates and their offspring
• Observed sex roles are the ones that
have provided the greatest fitness to
males and females – conflict is common!
- Females can raise families on their own
- Females do more work during hunting
- Females also take more risks
- Males claim shares from hunting work done by females
- When males die in a pride, it leaves females and cubs vulnerable as males are responsible for defending the pride (dangers: rogue males that kill cubs that are not theirs)
- Males won't care for cubs that are not their own

Step-parents are more
likely to use violence
against, & withdraw
resources from, their
children than are genetic
parents

Males are larger and stronger than
females, males have distinct facial hair
• Which sex is more ornamented?
• Bi-parental care  mutual mate choice
 both sexes have sexually selected
traits

Mutual assessment of partners through
coordinated movement and food
exchange
• Shared parental care
• Western grebe is an endangered
species
• Can be seen in Western Canada
- First routine involves imitation
- Run/dance together with coordinated timing
Give each other gifts after dancing (weeds)

A middle sized/medium gamete has lowest fitness
- Sperms are small and eggs are big - something in the middle won't work

A human egg is 100 microns
A sperm is 3 microns

Large in females
• Small in males and mobile
 Females are limited by resources to
gametes - they can invest in relatively
few gametes
 Males can produce many gametes –
they are limited by access to females

If the investment is equal (biparental care), then males choose females - less than females however still choosy

Orienting, tapping, singing, licking, attempting copulation, copulation
- Licking provides olfactory information on whether the female has mated before

Smell & taste= body-odour & flavour
composition: compatibility and quality
• Song: compatibility and quality
• Body size: larger is better (below a
species threshold)
• Recent matings (discriminat

12:3 preference by females that was more contrasting (artificially blackened)
Females also prefer birds that sing

Light intensities are too low for finding
food, making dawn the best time for
singing.
• The calm air at dawn is best for sound
transmission.
• Female fertility is highest at dawn.
- Nothing to eat at this time
- Messages travel far and are still recognizable
- Can allow birds to determine who is alive, their location and if there are any new males
- Birds listen to their specific frequency
- Invite females to patch
- Migrants add their voice
- Warblers can produce 50 different notes and never sing the same song 2x
- Nightingales are the most lyrical

Singing by males is used
– to attract females, and
– in male-male interactions (territorial
defence)

Some birds have large repertoire of songs
- Females prefer and are faster to choose males with larger repertoire

erritorial red-winged blackbirds were trapped
and their syrinx nerves were removed
• Control males had sham operation
Experimentally
muting birds
• Muted males had:
– more intrusions
– more fights
– more territory

Females that receive larger nuptial gifts
produce more eggs and perhaps have
longer lifespan

- Plateus after a cerain point (like 20 mins and not optimal to mate after that)
- Females mate quite quickly because they get free food so it is important for males to bring a larger size of food
- The most relevant/proper parameter is the male's fitness (number of offspring it can provide)

- Males with longer tails have fewer parasitic mites
- Males without parasites can be better fathers (sprayed males)
- They have more fledgeling and feldgeling shave larger body size
- Females have higher reproductive success

In many animals, the males contribute
only sperm (=genes) to the “family”
• That is, the males provide neither food
nor help in raising the offspring
• So direct benefit is less likely
Males do not provide any direct fitness to females

10 million birds prior to European
settlement
• The British Columbia population got extinct
due to habitat loss & hunting in 1918
• The remaining birds in Alberta and
Saskatchewan are closely monitored
• Alberta Fish and Wildlife counted only 66
males on leks in spring 2009
- Leks are monitored in other provinces like alberta

A new Canadian law from 2003
• Scientists (including myself) & NGO’s have
worked with the government on a bill that can
truly protect animals and plants
• Environmental organizations have won in
2012 a legal battle that required the federal
government to take further action for
protecting the sage grouse in Alberta

Ecojustice goes to court and uses the
power of the law to defend nature,
combat climate change, and fight for a
healthy environment for all.”
Sage grouse – Canada’s
most endangered species
• 2019: 400 individuals
Lek: cock of the rock video
clip
• The male’s contribution: sperm
transferred during a brief mating
• Two females made the same choice
64
65
66

The male’s contribution: sperm
transferred during a brief mating
• Two females made the same choice
- Each male owns a particular grass patch
- Have to persuade female to land beside him
- Bounce to attract female
- Females choose males by pecking them on neck
- Only one or two males end up mating when females choose the same ones

Males that are healthier, perhaps
because they have better genes, may
be more colourfu

Only weak evidence compared to very
convincing evidence for direct benefits
• Problem: there is no clear distinction
between direct benefits and good genes
• Example: males who seem to contribute
only sperm could also “contribute”
parasites / STD’s

MHC= Major Histocompatibility Complex – a
set of genes involved in immune response
• Large individual variation in MHC
(heterozygosity is higher than expected)
• Evidence from mice and rats that females
prefer males with MHC different than their
own
• Why?

- More evidence for compatible genes

Two explanations:
1. It provides better immune response
2. Preference for mates with different MHC
insures inbreeding avoidance

Inbreeding is associated with recessive genes that decrease fitness

Evidence from mice and rats that females
are sensitive to odours associated with
MHC, and that they prefer males with
different MHC than their own
• Do humans show similar sensitivity and
preference?

2 women and 4 men wore a T-shirt for 2
nights
• Then 60 men and 60 women had to rate
the 6 shirts based on intensity and
pleasantness
• All subjects had blood tests to
determine their MHC
Protocol
• Only 100% cotton, white T-shirts were
provided by the experimenters
• Shirts were placed in numbered
cardboard boxes covered with plastic
foil. A second layer of foil was changed
between subjects.
• Subjects smelled the shirt through a
small hole
- Intensity correlates to bad smell
- Subjects did not correctly identify the sex of the shrt wearer

Smeller found shirt-wearers that had unique MHC more pleasant
White bars indicate average amount of MHC that is shared

Out of 120 smellers

Random pattern in hatched bars

Consistent pattern in black bars

Genetic quality is often intuitive

Red line below zero means couples shared less MHC than expected

Assume that there are 2 gene loci in all
individuals (males and females):
1. Gene 1 codes for a certain male trait,
for example, bright colour
2. Gene 2 codes for female preference,
for example, for bright male colour
3. All individuals have these loci but
there is heritable individual variation
The runaway
• Females with stronger preferences for
brighter males have sons that are bright
and daughters that prefer bright males
• The colour and preference alleles may
become linked over time, meaning that
a stronger preference for brighter male
colour may be linked to brighter male
colour  a runaway process leading to
extreme male trait

Distance between two eyes
Weak but positive correlation for males with longer eyes spans

Selection on males with either longer or
shorter eye spans for 13 generations
• Females were not selected – each
generation, males were selected and
mated with unselected females
• Average difference of 1 mm in male eye
span between the short and long lines
after selection
Evolutionary change in eye span in
males was correlated with an
evolutionary change in preference in the
females

Until relatively recently, scientists
assumed that sexual behaviour in most
animals is innate
• Research in the past few decades has
indicated effects of individual and social
learning on sexual behaviour in a
variety of animals
• I have studied learning in the context of
sexual behaviour in fruit flies

Whom to mate with, where to look for mates, when a female is fertile and opportunies for extra pair copulations

- Yes
What factors determine it?
Age, culture, religion, class, education, income

Non-random mating based on
phenotype
• Positive assortative mating: the
tendency to mate with others of similar
phenotype
• Negative assortative mating: the
tendency to mate with others of distinct
phenotype

- Yes
MHC

Suppose we have a population of 100
male and 100 female white geese and
100 male and 100 female blue geese.
If they mate randomly, there will be 50 WW, 50 WB, 50 BW and 50 BB
Ratio of 1:1:2

Let eggs hatch in the lab
2. Split the chicks from parents of each
colour between foster parents of each
colour
3. (Note: the chicks are yellow)
If there was positive assortitaive mating based on foster parent colour (100 white, blue and males and females ): there would be 80 WW, 20 WB, 20 BW, 80 BB
Influence of mate choice comes from foster parents

A major factor causing speciation – the
formation of new species
• For example, strong assortative mating
could cause a split of snow geese into 2
species, white & blue

Does it result from phenotype matching
or imprinting on opposite-sex parent?
• If the later, women would also choose a
mate similar to their adoptive father

Focusing on adoptive parents - can split effects of genes and environment??

Subjects were asked to match photos of:
1. Focal woman and 4 possible husbands
2.Adoptive father when woman was a girl
and 4 possible husbands
3.Adoptive mother when woman was a girl
and 4 possible husbands

Husband-father is most significant

Women that were more emotionally attached to their adoptive father, married more emotionally similar men
udges found significant resemblance of
facial traits between a woman's
husband and her adoptive father.
• Girls who received more emotional
support from their adoptive father were
more likely to subsequently choose
mates similar to the adoptive father.

Definition: A female observer is more
likely to mate with the male that a
female demonstrator chooses

Female guppies typically prefer to mate with
more orange males
• The two males differed in the amount of
orange body colour from ~0% to 40%
Control: regular female choice with no
demonstrator
• Treatment: female demonstrator was always
placed next to the less orange male
- Placed in large aquarium, smaller one inside
Placed demonstrator female close to either male
Observer females
preferred the male that
demonstrator females
“preferred” as long as
the male was only
moderately less
orange
Observer thinks model knows what she is doing

Female copying increases variance in male reproductive success

Women and men observers rated the attractiveness of individual men's faces

Then the observers saw pairs of men's faces with a woman either smiling at one of them or having neutral facial expression and again rated their attractiveness

Predicted that women would be found more attractive if they smiled ?

0 = no change in attractiveness

Neutral face = decrease in attractiveness

Men who did not smile were more attractive

Direct interactions
• Extra-pair copulations
• Sneaking etc.

Rut -the annually recurring sexual
excitement in (some) male mammals
• Males smell female genitals to assess
receptivity
• Most ♂ - ♂ interactions involve only
mutual assessment
• Few result in fighting
• One ton charging at ~50 km/h
Roll around in their own pee, want to smell like their own territory

Only the strongest males hold harems
• 23% of harem holders have wounds
Variety of possibilities when they approach each other
Fight until one male withdraws
- Harem holders roar the most

formal armed
combat between 2
people in the
presence of
witnesses, to settle
differences or a
point of honour

Work by Nick Davies and his students
• Dunnocks have bi-parental care
•  male attempts to keep  male away
• Female seeks mating with  male
•  male verifies that female hasn’t
cheated on him
• Female gains from cheating on  male
Sneaking
• Occurs in many fish (with
external fertilization)
• The sneaker male is
smaller than the parental
male and sneaks to
fertilize eggs during
spawning
Alpha and younger male fight

Female can end up with beta

Alpha pecks out beta's sperm

Occurs in many fish (with
external fertilization)
• The sneaker male is
smaller than the parental
male and sneaks to
fertilize eggs during
spawning
• Midshipman fish (Sneaker
Males, Female, Parental Male)

Satellite males
• Mimic females,
confuse parental
males who attempt to
spawn with both
apparent females, at
which point they
release their own
sperm Parental male, female, satellite male

Sexual orientation - term used
for humans only
• Sexual preference – can be
measured in many animals;
may be labile
• Same-sex sexual behaviour
(=homosexual behaviour)

Why would animals engage in sexual
behaviors that do not directly result in
reproduction?
• The traditional puzzle assumes,
wrongly, that heterosexual sexual
behaviours typically result in
reproduction

Extended female sexuality:
heterosexual sex with no direct
reproductive benefits via conception
• Extended female sexuality is common
• Examples: scorpion flies, old world
primates

strous cycle of 36 days
• Sexual swelling for 14 days
• Fertile only for 3-4 days
Females solicit sex frequently during
sexual swelling and mate up to 5 times
per h with most males in the group

Material benefits (food, protection)
• Social bonding

• If extended heterosexuality is
common, why not same-sex
sexual behaviour
Typically, same-sex sex in
animals is not obligatory
• But there may still be
opportunity costs

Errors
The best explanation for male-
male courtship in fruit flies and
perhaps most insects
2. Used for initiating &
maintaining social relationships
3. Parental care by two females
when sex ratio is female biased

Male fruit flies court intensively
very young male
Male fruit flies spend similar times
courting immature males & females
Male courtship of mature
males is also prevalent

Very close relatives to us
Females engage in frequent same-
sex sexual behaviour
• Males do it but less often

Rates of genital contacts higher:
• post than pre conflict
• when food could be monopolized
and tension was high
Female genital contacts are best
explained as serving in
reconciliation and reducing tension
• However, genital contacts also
occurred independently of agonistic
encounters

Are associated with increased
levels of oxytocin (hormone
mediating social bonding)
• Are correlated with female bonding

Pairs of each species were
presented with food
• Researchers recorded:
–Frequency of co-feeding
–Sexual behaviour
–Play
–Aggression
Only in bonobos, aggression lower in both cases
A single individual was more
likely to monopolize the food in
chimps (97%) than in bonobos
(59%)

Social bonding that may lead to
material benefits (food, protection
- THis is based on correlations
- Chimps can show romantic attraction as well

Males and females look identical
Need genetic analysis to tell which is which
Sex ratio at Oahu: 59% ♀
• 31% of pairs were ♀-♀
• Half the female pairs remained
for 4 years, 1 pair for 19 years
• (Note: many birds show no sexual
dimorphism. DNA tests are needed
for sexing.)
- Heavily female biased
Female pairs had courtship displays,
& mutual grooming behavior
Hatching rate is related to fewer matings with males
♀-♀ pairs fledged fewer offspring
than ♂ -♀ pairs
• In most long-term ♀-♀ pairs, both
♀’s were the mothers (pairs raise
only 1 chick per year)

Prevalence is unknown
• Biased sex ratio and need for two
parents
• But why is the sexual behaviour
(courtship & mutual grooming)?

Innate tendency linked to pleasure
and pair bonding?

Sexual orientation
• Sexual identification
• Sexual behaviour
• The 3 are positively correlated,
but identification may be
under-reported
- Sexual identification of non-
heterosexual behaviour is
increasing
Reason: greater societal acceptance increases
identification, behaviour, or both

Five loci significantly associated with
same-sex sexual behavior

Rare mutation (1/15,000) typically
in the gene coding for the enzyme
21-hydroxylase
• Leads to fetal exposure to high
levels of testosterone
• 30% of CAH women aren’t
exclusively heterosexual,
compared to 5% in the general
population

Rare genes of large effect
• Many genes of small effect,
with currently unknown
functions

Humans show extended female
sexuality
There is no evolutionary
dilemma as long as same-sex
sex does not reduce fitness
• Has it reduced fitness over
evolutionary time? We don’t
know
• Does it reduce direct fitness
now?
SSB and fitness, UK
- Heterosexuals have higher fitness
- In thailand, there is similar fitnes between gays and lesbians

Likely answer: such genes, at
certain combinations, have
positive effects

Variation is not unusual in comparison to any other cognitive or physiological/anatomical trait
- SAME SEX BEHAVIOUR IS AFFETCED BY ENVIRONMENTAL FACTORS

Ray Blanchard, former
head of Clinical Sexology
Services in the Centre for
Addiction and Mental
Health (CAMH) in Toronto
and Tony Boegart

The tendency for older brothers
to increase the odds of
homosexuality in later born
males
Each additional older brother
increases the likelihood of
being gay by 33%
- Only significant for biological brothers

Only the number of older biological
brothers significantly predicted
homosexual behaviour
• Can explain a small proportion
(20%?) of gay men
• Not relevant either for gay men
with no older brothers or for
lesbians

Maternal antibodies to male-
specific proteins alter sexual
orientation
Mothers of gay sons with older
brothers will have higher
concentrations of antibodies for
the neuroligin 4Y protein than
mothers of heterosexual sons

Humans have 5 neuroligin genes
• Neuroligin 4 has X & Y versions
• Neurolligins mediate signalling
across the synapse
• Neuroligins have been linked to
social behavior in humans, mice
& flies

Because fetal material enters
maternal blood, women may
produce antibodies to the foreign
neurologin 4Y protein
• Such antibodies that enter the
fetus blood can bind to
neuroligin 4Y & alter sexual
orientation
Antibodies for neuroligin 4Y higher in
mothers of gay men (2018)
Antibodies for neuroligin 4Y higher
in mothers of gay men (2018)
• Results are consistent with the
predictions
• But no direct link between
neuroligin 4Y and sexual
orientation

Women don't have 4Y

Results are consistent with the
predictions
• But no direct link between
neuroligin 4Y and sexual
orientation

Same-sex sexual behaviour
occurs in many species
• Explanations: error, social
bonding, biased sex ratio,
mismatch between anatomical
& cognitive phenotype
Unknown and known genetic
factors (e.g. congenital adrenal
hyperplasia (CAH))
• Unknown and known
environmental factors (e.g.
maternal immune response)