Avoiding Predation Flashcards
What is an adaptation?
- A heritable trait that enhances the fitness of its bearers
- Either through current or past benefits and evolutionary history
Most behaviours are likely to be adaptive but why may some be non-adaptive?
- 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.
How is mobbing an adaptive behaviour in nesting gulls?
- 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.
Comparative method: If predator mobbing is not needed or not beneficial it will not occur.
Predictions and data
- 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.
What are anti-predator adaptations?
- Anti-detection
- Anti-attack
- Anti-capture
- Anti-consumption
Example of Anti-detection
Anti-predator adaptation
Crypsis (camouflage, transparency, nocturnality or subterranean living)
Examples of anti-attack
anti-predator adaptation
Stotting in Springbok, selfish herding, mimicry and warning colouration
Examples of anti-capture
anti-predator adaptation
Vigilance, run, swim or fly fast, body part autotomy (e.g. tail loss in lizards)
Examples of anti-consumption
Anti-predator adaptation
Fighting back, feigning death, releasing noxious chemicals, being hard to swallow (e.g. inflation by puffer fish)
Examples of types of camouflage
- Peppered moth
- Ground squirrels chew up rattlesnake skin and spread paste on their tails so they smell different.
Example of testing if camouflage works
- 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
Behaviour and comouflage: Decorator crabs example
- 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.
Why were decorator crabs with Dictyota less likely to be predated on?
Dictyota contains a chemical that repels omnivorous fish
* Choice of alga is an adaptation
Stotting by thompsons Gazelles
- 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
How can you test that the unprofitability hypothesis for stotting gazelles is correcrt?
- 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
