Avoiding predation

Question 1

Give 3 reasons why not every trait we see today are adaptations

Answer 1

1) Trait may have evolved to be adaptive to conditions of the past
2) Trait may have developed as an incidental side-effect of an adaptation (genetically linked)
3) Trait may be maladaptive, due to recent environ change that the animal has not yet evolved to

Question 2

Describe the comparative method of study on gull mobbing

Answer 2

• Nesting gulls mob intruders to protect the nest (risky though as may be injured)
• Comparitive method (tests evo hypotheses)
• Found that derived cliff-nesting species do not mob = mobbing is only beneficial to ground-nesting species

Question 3

Describe Anti-detection behaviours and give some examples

Answer 3

Crypsis
e.g camouflage, transparency, nocturnality, subterranean living

Question 4

Give some examples of anti-attack behaviours

Answer 4

Stotting in springbok, selfish herding, mimicry and warning colouration

Question 5

Give some examples of anti-capture behaviours

Answer 5

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

Question 6

Give some examples of anti-consumption behaviours

Answer 6

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

Question 7

How do decorater crabs use alga?

Answer 7

• Juvenile crabs decorate with Dictyota menstrualis for camoflage
• Predicted that decorated crabs will be less likely to be killed by predatory fish
  = true
• But also, crabs utilise a repellent chemical in the alga

Question 8

Describe the hypotheses trying to explain stotting in Gazelles, explain why correct/incorrect

Answer 8

• Unprofitability hypothesis: an honest signal of fitness to predators (correct as smaller proportion of stotters vs non-stotters are chased
• Anti-ambush: lets gazelles see whats ahead to reduce an ambush (incorrect bc stotting occurs in short grass too)
• Alarm signal: to warn conspecifics (indirect fitness) (incorrect bc even solitary gazelles stot)
• Social cohesion: enables groups to flee coordinately (incorrect bc solitary stotting)
• Confusion effect (incorrect bc solitary stotting)

Question 9

Describe the selfish herd effect

Answer 9

Herding decreases the chance of individuals being predated
= outliers have higher mortality

Question 10

Give an example of the herd effect determining group positioning

Answer 10

E.g Bluegill sunfish prefer to nest in the centre of groups where they are safer from egg predators

Question 11

Describe the dilution effect

Answer 11

The risk of being eaten is ‘diluted’ as group size increases

Question 12

Describe selfish herding in Whirligig Beetles

Answer 12

• Larger groups more attractive to predators
• But, in larger groups the predation rate per individual is lower
• They also experience a trade-off between food vs predation risk (food more abundant on the edge but predation risk is greater)

Question 13

Describe how the dilution effect effects Mayfly emergence

Answer 13

• Predation risk is lower when many adults emerge simultaneously (predators become satiated after eating a lower proportion of mayflies)
• This dilution leads to a sychrony of emergence e.g selfish herding in time

Question 14

Describe Kenwards study with piegon vigilance (1978)

Answer 14

Prediction: that individuals will react more quickly to a threat than lone individuals

Results: when predator model was present pigeons showed increased vigilance and total attack sucess declined in larger flocks

Question 15

Give a cost of group living and an example

Answer 15

More competition for food
E.g Sparrows may feed alone or in groups
- They make ‘chirrup’ sounds to attract others to them
- When predation risk is low = solitary
When risk is high = group