Lecture 5 - avoiding predation Flashcards
definition of an adaptation
a heritable trait that enhances the fitness of its bearers
- current benefits
- past benefits and evolutionary history
what is an important thing to remember about adaptations
not every factor that reduces predation is an adaptation against predation
what is anti-predator behaviour
the focus of intense natural selection
4 examples of an anti predator behaviour
1) being hard to detect (e.g. being cryptic)
2) to attack (e.g. being vigilant)
3) to capture (e..g being fast running)
4) to consume (e.g. the puffer fish swallows water to inflate into a spiny ball)
are anti-predator adaptations behavioural?
some are but some are often not primarily behavioural but may have a behavioural component e.g. animals that having warning colours rarely hide away and animals that are cryptic have to position themselves correctly
3 examples of non-adaptive traits
1) trait used to be adaptive to conditions in the past that no longer exist
2) the trait develops a maladaptive side effect of an otherwise adaptive proximate mechanism e.g. next to it is the the gene sequence
3) the trait is expressed as a maladaptive consequence of a recent environmental change
describe the antipredator adaptation mobbing
- Nesting gulls mob intruders
- Risky behaviour for the gulls
- experiments showed this to be a behavioural adaptation against egg predators that increases reproductive success
what is a comparative method?
- used when you cant carry out a successful experiment
- A method for testing evolutionary hypotheses, by comparing different taxa to see who does what, and correlating the occurrence of traits with the benefit of the trait
give an example of a comparative method
- if ground predator mobbing is not needed or not beneficial it ill not occur - e.g. wouldnt be needed in a cliff dwelling gull - this is proved by cliff neting kittiwakes not mobbing
example of how phylogenies can be used for comparative methods
- when looking at gull phylogenies cliff nesting is derived - mobbing evolved in ground nesting gulls but once cliff nesting evolved mobbing was lost as it no longer carried a benefit so is not worth the risk
- when comparing phylogenies of gulls and swallows the mobbing behaviour is lost in both cliff dwelling species of gulls and swallows - example of convergent evolution due to similar selection pressures
antipredator behaviours are extremely diverse - give 4 examples
1) antidetection -crypsis, e.g. camouflage, transparency, nocturnality, subterranean living
2) Anti-attack: Stotting in Springbok, selfish herding, mimicry and warning colouration
3) Anti-capture: vigilance, run, swim or fly fast, body part autotomy (e.g. tail loss in lizards)
4) Anti-consumption: fighting back, feigning death, releasing noxious chemicals, being hard to swallow (e.g. inflation by puffer fish)
what is important to remember about camouflage?
1) Camouflage may involve any of the senses, not just vision
2) Either (or both) prey and predator may be camouflaged
describe the experiment to test wether camouflage works
operant conditioning with blue jays
- trained captive blue-jays to respond to white underwing moths. 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
describe an animal which links behaviour and camouflage
decorator crab:
- Juvenile crabs preferentially decorate with Dictyota menstrualis - pile algae/ coral on their backs to hide from detection
- Crabs decorated with Dictyota will be less likely to be killed by predatory fish than crabs unable to use this alga
- The alga also contains a chemical that repels omnivorous fish
describe stotting behaviour in Thomsons gazelles
- When Thomson’s Gazelles spot a predator they may stot
- Stotting may signal to predators that “I’ve seen you” and “I’m very fit and ready to flee” = unprofitability hypothesis
- So predators don’t bother to chase animals that stot. Stotting is an honest signal
