Avoiding Predation

Question 1

What is an adaptation?

Answer 1

• A heritable trait that enhances the fitness of its bearers
• Either through current or past benefits and evolutionary history

Question 2

Most behaviours are likely to be adaptive but why may some be non-adaptive?

Answer 2

• Trait may have evolved under conditions from the past that no longer exist.
• Trait may have developed as an incidental side effect of anotherwise adaptive proximate mechanism.
• Trait may be a maladaptive consequence of a recent change in the environment.

Question 3

How is mobbing an adaptive behaviour in nesting gulls?

Answer 3

• Nesting gulls mob intruders
• Risky behaviour as they are at risk of injury/death
• Is mobbing a behavioural adaptation against predators?
• If mobbing is behavioural adaptation against egg predators, then mobbing should reduce egg predation
• Results of experiment by … showed that egg predation reduced closer to the colony
• Mobbing lowers predation of eggs and therefore increases reproductive success.

Question 4

Comparative method: If predator mobbing is not needed or not beneficial it will not occur.

Predictions and data

Answer 4

• Needs an accurate phylogeny to show evolutionary behaviours that have occured.
• Ground nesting is a earlier development - cliff nesting has evolved from that.
• Ground nesting gulls mob whereas cliff-nesters don’t mob
• Evolutionary pressure to lose risky behaviour when not needed.

Question 5

What are anti-predator adaptations?

Answer 5

• Anti-detection
• Anti-attack
• Anti-capture
• Anti-consumption

Question 6

Example of Anti-detection

Anti-predator adaptation

Answer 6

Crypsis (camouflage, transparency, nocturnality or subterranean living)

Question 7

Examples of anti-attack

anti-predator adaptation

Answer 7

Stotting in Springbok, selfish herding, mimicry and warning colouration

Question 8

Examples of anti-capture

anti-predator adaptation

Answer 8

Vigilance, run, swim or fly fast, body part autotomy (e.g. tail loss in lizards)

Question 9

Examples of anti-consumption

Anti-predator adaptation

Answer 9

Fighting back, feigning death, releasing noxious chemicals, being hard to swallow (e.g. inflation by puffer fish)

Question 10

Examples of types of camouflage

Answer 10

• Peppered moth
• Ground squirrels chew up rattlesnake skin and spread paste on their tails so they smell different.

Question 11

Example of testing if camouflage works

Answer 11

• Pietrewicz and Kamil tested blue-Jays ability to detect moths using operant conditioning
• Head up moths on pale bark hardest to detect
• Conclusions: behaviour of moths (i.e. where they settle) affects ability of birds to detect them

Question 12

Behaviour and comouflage: Decorator crabs example

Answer 12

• Decorate themselves with alga etc
• Juvenile crabs preferentially decorate with Dictyota menstrualis alga.
• Prediction: crabs with Dictyota will be less likely to be killed by predatory fish
• Result: Crabs with Dictyota get predated 5x slower than those without.

Question 13

Why were decorator crabs with Dictyota less likely to be predated on?

Answer 13

Dictyota contains a chemical that repels omnivorous fish
* Choice of alga is an adaptation

Question 14

Stotting by thompsons Gazelles

Answer 14

• Stotting = jumping high up
• Stotting may signal to predators that “I’ve seen you” and “I’m very fit and ready to flee”
• So predators don’t bother to chase animals that stot.
• Stotting is an honest signal.
• Unprofitability hypothesis
• Predators that chase stotting gazelles waste energy

Question 15

How can you test that the unprofitability hypothesis for stotting gazelles is correcrt?

Answer 15

• Test predation probability and successful capture in wild gazelles that stot against those that don’t
• A smaller number of stotters vs non-stotters were chased
• Predators failed to kill stotters
• Honest signal of quality

Question 16

What is the selfish herd theory?

Answer 16

• Game theory
• Prey bunch up and increase their chance of survival
• Dilution effect - bigger the group, lower the individual’s chance of being eaten

Question 17

Example of the selfish herd technique?

Answer 17

• Whirligig beetles - larger groups are more attractive to predators but they have a higher survival rate in larger groups
• Whirligigs have a trade-off - food is more abundant on the edge of a group but predator risk is higher on the edge

Question 18

Why is the selfish herd maladaptive to the group ?

Answer 18

• Predation may increase overall
• When bunched up the prey are a more tempting target
• Indivduals within the group still have lower mortality - hence the ‘selfish’ herd
• The selfish herd effect outweighs the increase in conspicuousness

Question 19

Group formation & vigilance

Answer 19

• Group formation may reduce predator attack/success via greater vigilance.
• E.g. pigeons
• Large flocks can spot a predator from further away
• Large flocks experience fewer successful predation attacks

Question 20

Vigilance in sparrows

Answer 20

Can feed alone or in groups

Prediction:

• When predation risk is low – solitary
• When predation risk is high – group