L7

Question 1

Adaptation definition

Answer 1

• A heritable trait that enhances the fitness of its bearer, through current or past benefits
  • Not every behavior is a current adaptations

Question 2

3 reasons why not all current traits are adaptations?

Answer 2

1. The trait evolved to conditions which no longer exist
   2. The trait develops as a maladaptive side effect of an otherwise adaptive proximate mechanism
   3. The trait is a maladaptive consequence of a recent environmental change

Question 3

Current benefits of mobbing in gulls

Answer 3

• Nesting gulls mob nest intruder
  • Risky behavior as they may be injured or killed
  • Must be a benefit as it is costly

Question 4

Prediction of why mobbing is beneficial

Answer 4

Mobbing distracts egg predators, so should reduce egg predation

Question 5

Mobbing experiment gulls method

Answer 5

• Placed a hens egg every 10 meters along a line stretching from outside to the middle of the colony
  • Measured mobbing and egg predation

Question 6

Mobbing experiment gulls result

Answer 6

• Mobbing behavior is greater inside the colony compared to outside colony
  • Egg predation is higher outside the colony than inside the colony
  • Supports that mobbing lowers predation and increases reproductive success

Question 7

The comparative method

Answer 7

• Tests evolutionary hypotheses by comparing different taxa to see who does what, and correlating the occurrence of traits with the benefit of the trait
  • Determines whether one factor causes another
  • Eg if mobbing is an adaptation we would expect it in species where it is necessary or effective in reducing predation, if it I not necessary it won’t occur

Question 8

Cliff nesters

Answer 8

• Wont mob intruders on the ground, but they will mob aerial predators
  • Data supports this
  • Eg foxes as they can’t access the cliff nest
  • When cliff nesting trait evolved mobbing was lost in cliff nesting species
  • Trait is lost over evolutionary time in similar species
  • Convergent evolution due to similar selection pressures

Question 9

The four behavioural components of antipredator adaptations

Answer 9

1. Anti- detection
   
   2. Anti- attack
   3. Anti-capture
   4. Anti- consumption
   • Some adaptations straddle many categories

Question 10

Anti- detection

Answer 10

• Crypsis
  
  • Eg camouflage, transparency, nocturnality, subterranean living

Question 11

Anti-attack

Answer 11

• Stotting in springbok, selfish herding, mimicry and warning coloration
  • Horned lizard blood spurting (poison)

Question 12

Anti- capture

Answer 12

• Vigilance
  
  • Run, swim or fly fast
  • Body part autonomy eg tail loss in lizards

Question 13

Anti- consumption

Answer 13

• Fighting back
  
  • Feigning death
  • Noxious chemical release
  • Being hard to swallow eg puffer fish

Question 14

Counter intuitive methods

Answer 14

• Some methods eg stotting seem counter intuitive as they appear to make themselves obvious to prey

Question 15

Camouflage in the peppered moth

Answer 15

• Two morphs light and dark
  • Both camouflaged to certain environments
  • Larvae are also camouflaged as twigs

Question 16

Camouflage

Answer 16

• Camouflage may involve any of the senses, not just vision
  • Either (or both) prey and predator may be camouflaged

Question 17

How effective is camouflage? Experiment

Answer 17

• Training captive blue-jays to respond to white underwing moths by looking at pictures of tree bark, if a moth was detected they would peck at a button and get a food reward
  • If they got it wrong they got no food

Question 18

How effective is camouflage? Experiment conclusions

Answer 18

• Jays detected fewer white moths on pale bark than dark bark, even worse at detecting head up moths on pale bark
  • Both resting location and orientation are important
  • Behaviour of moths i.e. where they settle affects ability of birds to detect them

Question 19

Decorator crab:

Answer 19

• Allow pile algae, corals etc to grow on their shells so they are hidden
  • Decorator crabs choose species to decorate themselves with
  • Prefer a specific algae

Question 20

Decorator crab experiment prediction

Answer 20

crabs decorated with preferred algae led to greater survival

Question 21

Decorator crab experiment results

Answer 21

preferred algae were 5 times less likely to be predated

Question 22

Decorator crab mechanism

Answer 22

are the crabs less visible or is the algae itself repellent?

- Algae contains a toxic chemical to omnivorous fish thus the crabs protect themselves

Question 23

Stotting in Thomson’s Gazelles

Answer 23

• Stot when they spot a predator
  • Jumping high into the air
  • Advertises itself to predator, may signal to predator it has seen predator, is ready to flee and is fit
  • Predators don’t chase animals that stot

Question 24

Unprofitability hypothesis

Answer 24

• Unprofitable to chase stotting animal

Question 25

Many hypotheses exist surrounding stotting behaviour

Answer 25

Only unprofitability hypotheses is likely to be correct- but how can we test this as opposed to some unidentified explanation?

Question 26

Stotting experimental data

Answer 26

• Lower proportion of stotters than non -stotters were chased
  • Predators chasing stotters never killed them, some non-stotters were killed

Question 27

The selfish herd

Answer 27

• Assuming a predator will move in any direction, so the best place for prey is to sit next to other prey to reduce chance itself will be targeted
  • This benefits the individual
  • But selfish herding may increase the total predation risk by making a more tempting target

Question 28

The selfish herd and groups

Answer 28

• If the bunched prey are a more tempting target it will increase predation overall
  • But individuals in groups can still have lower mortality if the selfish herd effect outweighs the increase in conspicuousness

Question 29

Selfish herd affect on positioning behaviour

Answer 29

• Bluegill sunfish prefer to nest in the centre of groups where they are safer from egg predators
  • Selfish herding depends on fitness payoffs for that individual

Question 30

The dilution effect

Answer 30

• Larger group lowers individuals chance of being killed
  • Assuming predators eat few prey

Question 31

Selfish herding in whirligig beetles

Answer 31

• Sit on top of water
  • Fish come up from below and consume
  • Larger groups are more attractive to predators
  • In larger groups the predation rate per individual is lower
  • Trade off in obtaining food versus predation risk. Food Is more abundant on edge of group as it has not het been consumed but predation risk is greater
  • Beetles experimentally food deprived tend to feed on group edge
  • Benefit of food outweighs risk
  • Selfish herding and dilution effect can influence the spacing of individuals
  • Can also affect timing of behaviour

Question 32

Mayfly emergence: dilution effect

Answer 32

• Freshwater
  
  • Adults fly above water for mates
  • Predation risk is greater on days when fewer mayfly emerge
  • Predatory birds become satiated
  • Dilution effect will lead to selection favouring greater synchrony of emergence

Question 33

Seabird laying and coral spawning

Answer 33

• Seabird egg- laying is synchronous. This may satiate gulls preying on fledging chicks
  • Coral spawning is synchronous. This may satiate animals preying on the gametes

Question 34

Group formation and vigilance

Answer 34

• In mayfly’s and beetles it only reduces success rate not the chance of a predator attacking
  • Being in a group sometimes reduces chance of predator attacking and the success rate by increasing vigilance
  • If one individual sees a predator it can warn the rest eg actively and by responding physically to predator warning other animals
  • As number of individuals increases, so does reaction distance to the predator
  • Gives birds more time to escape
  • For large flocks fewer attacks were successful

Question 35

Costs of group living

Answer 35

• More food competition
  • Sparrows may feed alone or in groups
  • When they form groups to chirrup to attract other sparrows

Question 36

Group living experiment predictions

Answer 36

• When predation risk is low = solitary, thus obtaining more food
  • When predation risk is high = group, less food but more survival chance

Question 37

Experimentally manipulated birds risk of predation:

Answer 37

• Eg distance to predator
  
  • Distance to safe cover
  • Sparrows made fewer chirrup calls when foraging close to safe cover and far from predator
  • Prefer to forage alone if predation is low, but if predation risk is high they will chirrup and form a group
  • Predator prey relations is an arms race