Lecture 5: Avoiding Predation Flashcards
what is an adaptation?
a heritable trait that enhances the fitness of it bearers
-through current benefits, or past benefits & evolutionary history
is every factor that reduces predation an adaption against predation?
NO
current benefits of Mobbing: Kruuk 1964
- nesting gulls mob intruders
- risky behaviour for gulls
- prediction: if mobbing is behavioural adaption against egg predators, then mobbing should reduce egg predation
- experiment: hens egg every 10m, outside gull colony & into gull colony
- results: inside colony more likely crows will attack predation, predation reduces as you enter colony
when would you use the comparative method?
when an experiment can’t be used
-way of comparing evolutionary hypothesis by comparing different taxa
e,g, of using a comparitive method: Mobbing
- two taxa (kittiwake - cliff gull, black headed gull - ground nesting gull)
- first gull = ground nesting
- kittiwake shouldn’t use mobbing as not necessary
- to use comparative method you need good phylogeny
- if some cliff did mob and some ground didn’t then prediction would be wrong
to use comparative method you need a strong
phylogeny method
antipredator adaptations 4 groups:
- Anti-detection
- Anti-attack
- Anti-capture
- Anti-consumption
anti detection example
Crypsis, e.g. camouflage, transparency, nocturnally, subterranean living
anti Attack examples
-stotting in Springbok, selfish herding, mimicry and warning colouration
anti capture examples:
Vigilance, run, swim or fly fast, body part autotomy (tail loss in lizards)
anti-consumption adaptations
fighting back, feigning death, releasing noxious chemicals, being hard to swallow (e.g. inflation by puffer fish)
camouflage: Peppered moth
- makes peppered moth less detectable to predators
- 2 subspecies; light form and melanic form
- larvae also camouflaged = dead twig
camouflage points to remember:
1) camouflage may involve any of the sense, not just vision
2) either (or both) prey / predator may be camouflaged
Testing whether camouflage words: Pietrewicz and Kamil
-trained captive blue-jays to respond to white underwing moths
-head up moths on pale bark hardest to detect!
Conclusions: behaviour of moths (where they settle) affects ability to detect them
–> so yea, it works
Behaviour & camouflage: Decorator crab
the crabs pile algae, sea anemones, coral on back to hide
- choosey about what species to decorate with, Dictyota menstrualis
- crabs without this species were 5 times more likely to be predated
- the alga contains a chemical that repels omnivorous fish
Stotting by Thomson’s Gazelles
- stot when see predator
- jump up in air with legs down, signal to predators ‘Ive seen you and I’m v fit and ready to flee’
Stotting by Thomson’s Gazelles: “Ive seen you and am ready to flee” is known as the what hypothesis
Unprofitability hypothesis == the likely hypothesis
Stotting by Thomson’s Gazelles: Anti ambush hypothesis
stating lets gazelles see what is ahead and reduces the chances they will be ambushed
–> but stotting occurs in all habitats including short grass
Stotting by Thomson’s Gazelles: Alarm signal hypothesis
sotting warns conspecifics, especially offspring that predator is near
–> but even solitary animals Stot
Stotting by Thomson’s Gazelles: Social cohesion hypothesis
stotting enables gazelles to form groups & flee in a coordinated manner
-but solitary animals stot
Stotting by Thomson’s Gazelles: confusion effect hypothesis
- stotting confuses and distracts a predator preventing it focusing on one animal
- but solitary animals stot
Stotting by Thomson’s Gazelles: is it an indicator of quality?
YES, lower proportion of stotters, than non stotters chased & predators fail to kill stotters
-honest signal of animals health
The selfish herd: Snake in pond where safest place for frog to sit
- frogs best close to other frog
- snake attacks then no individual target, selfish strategy
- benefits individual, but not group (if all sat together may make a bigger target bad for group)
selfish herd is an example of
Game theory
