Animal Behavior Midterm 1

territory

•  smaller, actively defended from conspecific intruders, contains a key resource 

Home range 

•  larger, undefended area used by individual can overlap with other individuals 

  • Spatial extent at individual level is made up of the territory and home range 

• Leaving range for long period is migration 

Species range

• full extent of species geographic distribution 

What is migration and why does it evolve

• ersistent, undistracted locomotion 

  • Not wishy-washy 

• Relocation on a greater scale and duration than daily movements 

• Relocation between regions with alternating favorable and unfavourable conditions 

  • Migration is an adaptation that increases fitness 

• About 20% of bird species are migratory 

  • Some cases can cause birds to change from being migratory to being non migratory 

• Cuckoo bird lays their eggs in the nest of another bird and the mother bird over extends herself to feed the bird 

  • Cuckoo bird follows its own species migration pattern and migrates to the same location as its parents 

Three major drivers of migration 

• Unpredictable changes (weather, food resources, predators, shelter) 

• Competition for resources among conspecifics ( food, breeding sites) 

  • All species cannot have the same pattern because then there is too much competition for resources 

• Predictably unfavorable environmental conditions (annual cycles) 

Normal migration

• all individuals or populations of a species move between ecological zones 

partial migration

some individuals or populations migrate while others remain resident

Internal Circannual Rhythm 

• Controls annual life cycle 

• Hormonal change → restlessness (zugunruhe) 

• Physiological changes prepare for migration 

  • Increase caloric intake and body fat 

    • Fat is much lighter than muscle

  • Increase gut size, flight and cardiac muscle hypertrophy 

  • Feathers molt 

    • Grow specialized feathers for long distance flight

• Physiological changes (migration)

  • Go from hyperphagia to hypophagia 

  • Regression of gut, gizzard liver (reduce weight)

    • Because they are not eating while flying 

• Once they land, they cannot eat because their gut is still too small to digest food 

Example in Munich of the change in bird migratory patterns due to urbanization

• Males and females in the forest both migrate to Egypt 

• In cities, males became sedentary 

• Outside of breeding season, males and females do not interact 

 

• Males are larger and may be able to survive winter better 

• May rely on human food 

most important cues for far range migration

• Map step 

  • Know the bearing and the distance of the migration goal 

  • Maps are learned, innate or both 

  • Maps are often multimodal (olfaction, magnetic field, landmarks etc) 

• Compass step 

  • You know where North is and therefore all other directions 

    • Use poles 

    • Use celestial maps of stars or the sun 

most important cues for near range migration

• Most important cues 

  • Using local landmarks 

• Near range →Example of Gannets 

  • They don’t leave their local area unless they have to 

  • They have to meander in a random pattern until they start to recognize their local landmarks 

  • Some birds never encounter their familiar landmarks and never go home 

map vs compass

• A map is a representation of physical space that allows you to determine where you are here you want to go, and how to get there.

• compass allows you to orient the map to the physical directions of the world

Beehive Experiment with von Frisk

• Training with sunlight exposure for bees

  • Place food source in a specific location 

  • Once they find the food they go and come back 

  • Testing whether they use odor sensing to see the location 

  • Food vs observer 

    • Change the odor of both 

  • Change orientation of hive, hive is moved to a new area 

    • Takes place at all times of day 

    • They always go where the food source used to be

    • Food aligned with sun position

• Can use sun as compass because it has fixed movement 

• Must account for its movement relative to fixed features of the Earth surface 

• At a later time, would they follow sun or food 

  • Straight to food 

Homing Pigeon example

Release in Maine area =

They will return back to their original 

At 9pm 

• Train bees at 9 pm and 9 am separately 

• Train them to do different at 9 amd 9pm 

how do bees know how far to go

• Honey bee waggle dance to communicate food sources 

• What to do when its too bright outside 

  • Compound eyes allow to translate rays of light into a polarized version → humans can learn but we are not good 

• Will see polarized light in different orientations 

• ALlows to create a very precise compass 

• Desert ants (ft, in paper) 

• Sun can be used even in a very cloudy day 

• Our eyes cannot see polarized light

Magnetic Fields and navigation in pigeons

• Pigeons always made a b line back to their loft 

• On cloudy days they had a much harder time. 

• When  new technician Dwayne did the experiment, the birds could not return to Ithaca 

  • Turns out the one difference is that Dwayne drove a European car, and the birds were in the backseat 

  • Engine is in the back of the car, disorients the birds 

  • The magnetic coils in the engine have a very high magnetic field 

  • Messes up the birds ability to sense the Earth’s magnetic field 

• Another lab continued these experiments 

  • Put magnets on the head of the birds and change the magnet polarity

  • Do the experiment in sunny and cloudy environments 

  • When sun compass is available they ignore the magnetic information 

  • When sun compass is not available, they use the magnetic compass 

    • When magnet is reversed on a cloudy day, they fly in the opposite direction of where they should 

• Makes it disadvantageous to only follow the magnetic compass of the poles as a species 

• closer you get to the poles, the more vertical it gets 

• At the equator, the magnetic field is parallel 

• It is these lines that are followed by the birds 

• There are anomalies in the magnetic field lines around the Earth, particularly in the South of the world 

  • Can also indicate that you are in that position 

• Birds are sensitive to the inclination angle and the strength of the field 

• Compass can act as a map

• Birds can actually see magnetic fields as color 

  • Blue/green light → no disorientation 

  • Red/yellow light (something not typically seen at dusk) → the birds get messed up. 

• Are magnetic fields only processed in the eyes? 

  • Probably not 

• Iron-mineral based hypothesis 

  • Movement of iron minerals in the trigeminal nerves could be reacting to magnetic fields 

• Light-dependent hypothesis 

  • Photoreceptors 

  • Songbirds that are very good at migration have cytochromes in their eye cells 

• Dark spot in the birds vision indicates direction of gravitational field, and will get darker when it is at a higher incline of the field lines, the spot will darken 

Logger Head Turtle Example

• Endangered species 

• At night, little turtles hatch and immediately go towards water 

• Cues they use 

  • Follow moonlight towards the water. 

    • However, with humans and beach front homes, the light pollution confuses the turtles and they would go to condos 

    • Also because turtles would go to a specific light frequency that was being used in the condo lights → change light frequency 

  • Goal is for turtles to swim perpendicular to waves and want to hit the water stream in the ocean 

  • Difficulty near North Atlantic current because that would take them to an area that is too cold 

    • At this point, the turtles should exhibit a change in behavior and swim downwards in another direction 

    • At this point, the cue they are looking for is using Earth’s magnetic field

      • Study by putting little turtles in tanks where they artificially change the Earth’s magnetic field 

      • When presented with the corresponding inclination angle, they all swim southwards 

Navigation Cues Summary

Ideal Free Distribution 

• Dung Beetle example 
  

• Individuals move freely across habitats to forage 

• Individuals are distributed according to the resource abundance 

• Fitness benefits are equal among individuals

• Put more food on one side, always ends up with 2 fish/4 fish 

• Example of grocery lines 

• Numbers are fluid/ strategy is fluid 

  • Example of phenotypic plasticity (change behavior due to resources in the environment) 

• Dung beetle males compete for females 

  • Gets less fertile → less females present  

  • Some males are still present on poor dung patches 

    • Some wait until the end 

  • Dung dries up over time to it gets less ideal to pay eggs on 

• No inherent competition → doesn’t really happen IRL 

• Everyone is spaced out evenly so that they can optimize getting everyone’s needs met 

  • Too many individuals on rich habitat → might be beneficial to move to the lower resource patch instead 

• Ideal Free Distribution 

  • Individual choose best habitat available to them 

  • Habitats should be filled so that the profitability for an individual is the same in each one 

  • Decisions about where to settle depends upon what others in population are doing

    • Example of phenotypic plasticity 

despotic distribution

• I claim the room for myself 

• Everyone has their own territory and they fight 

• Sneakers are often younge males that get access to resources by sneaking around the richer habitat and sneak-mating with females 

• Territory is an area defended by animals against others 

• Animals will fight fiercely over this territory 

• Dragonfly may have territory of a single leaf 

• Woodpeckers would get a hole as their territory in many species the male is more likely to be defending 

• Also territory defense where females defend against females and males defend against males

•  meerkats will fight to death because the desert resources are scarce

• Despotic Distribution 

  • Aggressive protection of resources 

    • Has a big metabolic cost to fight 

  • Once good territory is gone, it is gone → they might have to change up their strategy 

Factors influencing territoriality

• Resource quality 

• Resource distribution in space and time 

• Nature of competition for resources 

what happens to territoriality if there is even food distribution?

there is no territorial behavior

• Small food clumps → territorial behavior 

• Large food clumps → no territorial behavior 

explain these graphs

• Dynamics of territory size 

  • Territory size and flower density per m^2 

  • Rainfall increases, percent time spent foraging 

  • Golden winged sunbird is a specialist who has a beak designed to fit a certain kind of flower 

• Y axis → amount of time spent foraging (during dry season, more than half your day), during rainy season it’s not bad

• They are only territorial when there is nectar present in the flowers and only when it’s a limited amount

  • When there is no nectar there is no territory to defend 

  • When there is an abundance of nectar there is enough that they don’t need to be territorial 

  • Measure metabolic cost (in lab) 

  • Look at behavior in field 

  • Calculate energy saved minus the perching compensation time 

  • Where do you use more calories? Seems like defending costs more calories than it is beneficial 

    • This means defending is less beneficial. 

    • More individuals around → must be more territorial 

Is territoriality flexible?

Yes Birds can defend, adjust size of territory, maintain or abandon territory size, etc. 

• Natural selection favors complex behavior that is NOT genetically fixed. 

Evolutionary Stable Strategy

• Strategies in populations that are evolutionarily stable 

• Game theory 

• Works in cases with limited resources 

• Look at examples in the animal world and how these dynamics can explain them

•  ESS Strategy → if adopted by all members in the population it cannot be bettered by an alternative strategy 

  • Examples sitting at a concert is NOT an ESS (bc it can be invaded by a better strategy) 

    • Since a few people can still stand up, they will invade my strategy and this introduces a new strategy making sitting not an ESS 

  • Example of fishing in gulls (might not be an ESS because it can be invaded by birds that don’t want to hunt and instead will steal ) 

    • What is the new stable strategy? 

      • Everyone can’t steal and everyone can’t fish 

      • New strategy → mixed strategy

      • What is the optimal percentage of each animal being involved in the strategy 

Hawk and dove game + calculations 

hawk and dove are not species of animals, are representative of behaviors 

• Version of game theory 

• Territory defense and fighting are costly in terms of time, energy and risk of injury or predation 

  • Injury is costly 

• Best strategy between being an aggressive fighter or being submissive/sharing 

  • Animals can change strategy based on the situation 

• Used to protect resources, and based on what others are doing in the population

  • Ex. predators eat all of the morphs that are most frequent in the population, then second most frequent etc. 

• Hawk always fights and may injure opponents, they also run the risk of injuring themselves 

• Doves never fight 

  • What is the optimal strategy in the population? 

In this population, the stable strategy is not to be a hawk because there is a possibility of me losing against another hawk 

• Could also be fitness benefits such as access to a mate Changes the relationships between when it is beneficial to be a hawk and when it is beneficial to be a dove

• Given cost and resource/value numbers to plug into the equation and find then when the system is at equilibrium 

• Being a hawk or dove is not a fixed trait

*Instead of finding f at equilibrium can also calculate over the range to see the comparison for different percentages of either hawk or dove behavior 

• Equilibrium point indicated is where everyone benefits the most 

• If there are very few doves in the area but several hawks, 

  • Advantageous to be a dove because hawks will infight 

  • Even if I get resources taken, I don’t incur a cost 

• If there are many doves but few hawks it is beneficial to be a hawk because i only encounter doves from whom I can easily steal resources

• These scenarios are rare because animal would convert their behavior to the advantageous type until it is no longer advantageous 

  • Top of the y axis is the fitness benefit and the bottom is the fitness cost 

• Balance can be shifted based on the value of the resource in the context and the value of the cost in the context 

Fighting Between Male Fig Wasps

• Infertile eggs → female 

• Fertile eggs → males 

• Figs have infertile eggs of female wasps in them 

• They emergy 

  • Males emerge before females → they are built to fight 

  • Goal is to fight other males to copulate with the unborn females 

  • They copulate with females before they are born 

  • Then they bore a hole in the figs and allow the females to leave where they lay eggs in a new fig 

• High cost and high rewards 

Mixed Strategy Examples → Capercaillie bird and toads WILL BE ON MIDTERM PROLLY

Capercaillie Bird Example 

• Capercaillie only acts as a hawk during certain parts of the year 

  • Individuals adopt a mixed strategy playing hawk n% of the time and dove (1-n)% of the time 

Toad Example of Mixed Strategy 

• Large male (60%) mating call (super loud) 

• Smaller (satellite) male (40%) → sneaker 

  • Males cannot cheat on their call and change the sound or anything 

• Phonotaxis Experiment 

  • Play calls around females in a box or something idk using a speaker 

  • Females always go to the male frogs 

• Smaller males have a higher chance of not being preyed upon 

  • Wait until the female is going towards a large male, and then they sneakily jump on the female and copulate 

  • Based on the call behavior and volume of an individual frog, it can impact the likelihood of them adopting a specific phenotype 

  • If the neighbor has a 4x louder call, will choose to stay silent and adopt the sneakier behavior 

explain this graph

• Large male (60%) mating call (super loud) 

• Smaller (satellite) male (40%) → sneaker 

  • Males cannot cheat on their call and change the sound or anything 

• Phonotaxis Experiment 

  • Play calls around females in a box or something idk using a speaker 

  • Females always go to the male frogs 

• Smaller males have a higher chance of not being preyed upon 

  • Wait until the female is going towards a large male, and then they sneakily jump on the female and copulate 

  • Based on the call behavior and volume of an individual frog, it can impact the likelihood of them adopting a specific phenotype 

  • If the neighbor has a 4x louder call, will choose to stay silent and adopt the sneakier behavior 

  • Frogs are born with different morphs → smaller causes them to be quieter and larger causes them to be louder

    If you are louder than your neighbor you will make a sound

    If you are quieter than your neighbor you won’t 

Evolutionarily stable polymorphic state → sand piker lizards, guppy fish, sand pipers

• Guppy fish with five different morphs 

• Sand piker lizard example 

  • Three different colors (yellow red blue orange)

  • Fixed evolutionary measures to maintain the relationship between these males and their morphs 

    • Red blue yellow and orange are genotypically different 

• Morph can also be based on diet in other animals, such as beetle 

• Sandpipers 

  • Fluff feathers to attract females 

• Three kinds of males are present in the population 

  • All of them have different fitness characteristics 

Group size determinants 

• Depends on the cost of being in the group 

• Group sizes are dynamic based on the circumstances around them 

  • Feeding Rate 

    • Is it determined by dominant or subordinate? 

      • It’s determined by the subordinate 

      • Subordinate birds tend to have a larger group size 

    • Who determines the group size? 

      • Dominant birds chase the subordinate away? 

      • No → subordinate determine the group size. 

      • Subordinate vs Dominant 

        • Alone → same feeding rate 

        • In group → in a group, subordinate loses more food while the dominant will steal more food 

• Dominant always wants to be in a group 

• Subordinate gets less advantage because the dominants in the group would steal their food 

• Hawks in a group are able to hunt prey they would not be able to hunt alone 

  • Did not intentionally coordinate 

• Chimpanzees each have a role or function in the group 

Animal Communication 

• Required reading of the animal communication chapter 

• At human language you can stop 

• Communication 

  • Simple is between two individuals 

  • Subject A is the Sender and Subject B is the receiver 

    • Receiver makes a decision on whether to respond or not to respond 

  • Intentional signaling from one individual (sender) to another (receiver) that affects the current or future behaviors of the receiver 

    • Example with birds 

    • Put female bird in a cage and playing the sound of a male song 

      • Causes female to present herself for copulation 

      • After a long time of hearing song, causes elevated hormone levels in female that make her more receptive to the male 

    • Signal evolved due to the effects it has on the receiver 

    • Signalling impacts the fitness of one or both individuals 

      • Increases my fitness if I have a strong song that draws in a female 

      • Increases female fitness because she can copulate and pass on her genes 

• Acoustic signaling 

  • Sound in birds, fish, whales etc 

  • Can be heard or not 

    • Can also be vibrations instead 

• Visual 

  • Can be movement, color, and positioning 

  • Dog signal scared when hunch its back 

• Chemical 

  • Smell 

  • Pheromone trail 

  • Scent marker 

  • Dung scent → rhinos can tell the age and the testosterone levels of the male that shat there 

  • Trophallaxis → sharing information by exchanging fluids via mouth 

    • Partially nutritional, but they use it to share chemicals with each other 

• Tactile 

  • Physical touch 

• Electric 

  • Fish produce weak electrical signals in murky water that allows them to transmit information about food source, group, quality etc 

• Pre-existing trait hypothesis; from cue to signal 

• Sender: exhibits pre-existing traits (ex. Behavioral, physiological, and or morphological) that provides cues to receivers 

• If exaggeration of these cues can increase reproductive fitness, natural selection will act on them causing these cues to evolve into communication signals 

• Ritualization -> transformation of cue to signal 

  • Example → piloerection (feather or fur stick up) creates like a cushion of air around their bodies that acts like an insulator

• Topknot in birds → feather on top of head can be moved using piloerection 

• Dominant male will put their feather forwards while the submissive male will pull his backwards 

Not a communication signal

• If I sweat, allowing mosquitoes to be more attracted to me, I am not communication 

  • This is an unintentional signal 

  • Secondary effect of a physiological response is a cue rather than a signal 

• Another example 

  • Frog, body shape signals to the predator that the predator should eat it 

    • Not a communication signal, it is only a cue 

    • Cue does not evolve due to the effects it has on the receiver 

  • Red coloration of frog would be communication if it is an example of aposematic signalling 

    • This also increases its fitness because it makes it less likely to be eaten by a predator 

      • Predator receives signal as not wanting to each something that is poisonous

index signal

honest signals that cannot be faked

Physical constraint

How do animals decide how to behave in contests?

When should they be hawks and when should they be doves?

Natural selection favors ‘displays’ because..

It ensures that strongest (dominant) individuals win contests

Protects subordinate animals for costly fights

Multimodal 

• Australian jumping peacock spider 

• Male spider use jumping and color display 

• McGurk Effect → how you perceive multimodal signals 

Signal Reliability and Signal Honesty 

• Frequency of roar correlates with the size 

• Signal reliability → signal is reliable when it is consistently (on avg) correlated with some attribute of the signaler (ex. Body size) or the signaler’s environment 

  • Need to prevent lying and cheating because otherwise communication cannot be trusted 

  • Ex roar sound being shaped by the size of the vocal cord of the animal → helps to estimate the size of animal 

    • These deer are able to change their larynx size to make themselves seem bigger → then everyone can lower their larynx → everyone goes as low as they can and it ends up representative of their body size 

  • Signal Reliability and Conflicts of Interest examples 

    • Cuckoo bird example, the bird presents yellow dots on their wings to make mother think there are three beaks 

    • Drongo bird learns alarm calls from another bird species, approach other bird species when they have foraged food, and then make an alarm call when they are there and eats their food 

      • Changes the species they target so the target species does not catch on 

what are types of displays that ensure signal honesty?

• Index signal (signal indicating the body size) 

• Handicap signal (body appendage that can be costly) 

• Badge of status signal (low cost body appearance)

  • Socially shamed if the signal is faked 

• Nonequilibrium/non-informational signaling 

• Example here is manipulation of corn moth and the water mite too 

  • Read textbook 

• Sensor bias → sensory and neural systems have biases that have evolved in other contexts 

• Sensory exploitation → signalers evolve signals that exploit these biases 

  • Receiver has no choice due to exploitation of an ancestral/evolutionary trait 

• Sensor bias

• Sensor bias → sensory and neural systems have biases that have evolved in other contexts 

• Sensory exploitation

• signalers evolve signals that exploit these biases 

  • Receiver has no choice due to exploitation of an ancestral/evolutionary trait

• Corn moth example 

• Coexist with bats for 150 million years 

• What sender wants from receiver is not always what the receiver wants from the sender 

• Male vs female 

  • Male wants to inseminate every female possible 

  • Female wants to be picky because it takes a lot of energy to have eggs 

• Batesian mimicry can also be by sound 

• Hypothesized evolutionary timeline 

  • Moths evolve ultrasonic hearing to detect bats and trigger escape response 

  • Some moths evolve ultrasonic communication for 

    • Signal aposematism 

    • To jam the bat signal 

  • Some moths can co opted response of female moths to ultrasound for mating purposes 

• Moth strategies 

  • Moth hearing bat sonar signals → they start evasively flying if they are nearby 

  • If they are far away, they freeze and hope the bat doesn’t notice them 

  • 3 cm away female can’t hear the male 

  • Once it gets to copulation range, it sounds much louder 

  • Low intensity sound induces a freezing response in the female → coopts ancestral freezing response and the female is paralyzed and copulated with by the male 

  • Loud sound of bat song compared to courtship call 

    • Louder call = wiggle around more for bat call 

    • Louder call for courtship = avoidance as well 

  • Since female has no choice then there is no i

  • Information and response 

Eusocial communication 

• Honeybees are computing distance using optic flow 

• Return to hive and want to communicate with them 

  • Waggle dance 

  • WE NEED TO KNOW HOW THE WAGGLE DANCE WORKS 

• Longer time spent doing the dance = further distance from the food source 

  • Based on energy expenditure, if it’s windy they may do a longer dance because it takes more energy 

Red deer example of index signaling

• Red deer are protecting resource of females 

• Roar is hard to cheat because it is tied to their body size → evolved some tricks to create a dishonest signal 

  • Cheating link between body size and roar volume, except everyone started doing this so it ended up matching the body size again 

  • Red deer have a vocal tract and a larynx (Adam’s apple) and a trachea that extends to lungs 

    • Length of vocal tract is related to overall body size 

    • Present roar on a spectrogram/sonogram 

      • Two seconds in length 

      • Greyness = loudness 

      • Pitch is a property of the larynx 

        • However, pitch is not a reliable measurement of body size 

      • Formants → property of vocal tract 

        • More reliable measure of vocal tract 

        • Correlates with vocal tract length 

      • Compare vocal tract length with the log body weight 

        • Estimated vocal tract length and reproductive success have a positive correlation 

Parallel Walk

• They walk past each other multiple times to size each other up 

• The closer they are in size, the more likely they are to spend more time evaluating each other 

  • Also takes place in male cichlid fish 

Handicap Signal 

• Body appendage 

• These are mostly honest signals because dishonesty is possible but not profitable 

  • Examples are peafowl, stalk-eyed fly 

• Handicap principle (Zahavi) 

  • signals can be honest if they are costly

There is a cost for dishonesty in this system 

• Ex. signing up to run a marathon with a friend and you can’t run at all 

• Benefit here → reproductive success 

• Signal intensity → low cost signal = low benefit 

  • Increase cost signal = increase in benefit and increase in cost 

  • Middle black line indicates the maximum profit for the animal 

  • Can’t die year 1 → lose opportunities for mating 

Wolf Spider Handicap Signaling example

• Tap their limbs on the ground 

  • Used to doing it on leafy material 

  • Sends signal to other spiders as a part of a courtship ritual 

• Females do prefer males that drum/thump 

• Females prefer males that do more thumps 

  • Three different categories of male and calculate their drumming rate (they only drum when there are females) 

  • High, medium, low fitness group 

  • How do I generate these three groups? 

    • Took spiders and gave them varying nutritional regiments 

  • Drumming is energetically costly 

Stalk Eyed Flies

• Costly for the males to produce a stalk 

• Big stalked male is preferred by female 

• Gave different diets to different flies 

• Measure wing size for fitness and eye stalk for female preference 

  • Males put more energy into making their eyestalks longer 

  • If there is less energy available, the males must make a decision to prioritize eye growth or wing growth 

  • Only males that are very robust, strong, high quality can grow the eyestalk. 

• Can try to grow large eyestalks even if you don’t have energy 

• Bigger eye = bigger body = stronger

• They choose to grow their eyes !! not like deer 

Badge of Status

• Social shaming 

  • Color feather in songbirds is related to testosterone levels and some birds try to cheat the system, but then you get socially shamed by your group 

• Paper wasps 

• Color marks on their faces 

  • Number of markings are tied to diet and dominance in the group 

  • Use sharpie to change the number of markings 

    • Less dots = more subordinate 

    • More dots = more dominant 

  • Put two wasps together and make them fight 

    • More dots always wins, then you can do brackets and see who is the most dominant and least dominant 

  • Place dead wasp near food source 

    • Wasps always go to the foodsource where there is a less dominant male (dead) by it 

    • Choose to avoid conflict 

• Cheat system 

  • Pair together the fake dominant with the fake submissive 

  • When the fake submissive one wins, the cheating (fake dominant)  wasp gets socially harassed 

  • Badge Cost 

    • Energetics → costly to produce, weak individuals do not have it 

  • Social cost 

    • Get bullied