L7 Flashcards
1
Q
Adaptation definition
A
- A heritable trait that enhances the fitness of its bearer, through current or past benefits
- Not every behavior is a current adaptations
2
Q
3 reasons why not all current traits are adaptations?
A
- The trait evolved to conditions which no longer exist
- The trait develops as a maladaptive side effect of an otherwise adaptive proximate mechanism
- The trait is a maladaptive consequence of a recent environmental change
3
Q
Current benefits of mobbing in gulls
A
- Nesting gulls mob nest intruder
- Risky behavior as they may be injured or killed
- Must be a benefit as it is costly
4
Q
Prediction of why mobbing is beneficial
A
Mobbing distracts egg predators, so should reduce egg predation
5
Q
Mobbing experiment gulls method
A
- Placed a hens egg every 10 meters along a line stretching from outside to the middle of the colony
- Measured mobbing and egg predation
6
Q
Mobbing experiment gulls result
A
- 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
7
Q
The comparative method
A
- 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
8
Q
Cliff nesters
A
- 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
9
Q
The four behavioural components of antipredator adaptations
A
- Anti- detection
- Anti- attack
- Anti-capture
- Anti- consumption
- Some adaptations straddle many categories
10
Q
Anti- detection
A
- Crypsis
- Eg camouflage, transparency, nocturnality, subterranean living
11
Q
Anti-attack
A
- Stotting in springbok, selfish herding, mimicry and warning coloration
- Horned lizard blood spurting (poison)
12
Q
Anti- capture
A
- Vigilance
- Run, swim or fly fast
- Body part autonomy eg tail loss in lizards
13
Q
Anti- consumption
A
- Fighting back
- Feigning death
- Noxious chemical release
- Being hard to swallow eg puffer fish
14
Q
Counter intuitive methods
A
- Some methods eg stotting seem counter intuitive as they appear to make themselves obvious to prey
15
Q
Camouflage in the peppered moth
A
- Two morphs light and dark
- Both camouflaged to certain environments
- Larvae are also camouflaged as twigs
16
Q
Camouflage
A
- Camouflage may involve any of the senses, not just vision
- Either (or both) prey and predator may be camouflaged
17
Q
How effective is camouflage? Experiment
A
- 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
18
Q
How effective is camouflage? Experiment conclusions
A
- 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
19
Q
Decorator crab:
A
- 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
20
Q
Decorator crab experiment prediction
A
crabs decorated with preferred algae led to greater survival
21
Q
Decorator crab experiment results
A
preferred algae were 5 times less likely to be predated
22
Q
Decorator crab mechanism
A
are the crabs less visible or is the algae itself repellent?
- Algae contains a toxic chemical to omnivorous fish thus the crabs protect themselves
23
Q
Stotting in Thomson’s Gazelles
A
- 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
24
Q
Unprofitability hypothesis
A
- Unprofitable to chase stotting animal
25
Many hypotheses exist surrounding stotting behaviour
Only unprofitability hypotheses is likely to be correct- but how can we test this as opposed to some unidentified explanation?
26
Stotting experimental data
- Lower proportion of stotters than non -stotters were chased
- Predators chasing stotters never killed them, some non-stotters were killed
27
The selfish herd
- 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
28
The selfish herd and groups
- 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
29
Selfish herd affect on positioning behaviour
- 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
30
The dilution effect
- Larger group lowers individuals chance of being killed
- Assuming predators eat few prey
31
Selfish herding in whirligig beetles
- 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
32
Mayfly emergence: dilution effect
- 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
33
Seabird laying and coral spawning
- 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
34
Group formation and vigilance
- 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
35
Costs of group living
- More food competition
- Sparrows may feed alone or in groups
- When they form groups to chirrup to attract other sparrows
36
Group living experiment predictions
- When predation risk is low = solitary, thus obtaining more food
- When predation risk is high = group, less food but more survival chance
37
Experimentally manipulated birds risk of predation:
- 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
