Avoiding Predation Flashcards
Antipredator behaviour: example of adaptive behaviour
Detection avoidance
Attack avoidance behaviour
Selfish herding
What is an adaptation?
Heritable trait that enhances the fitness of its bearers
Current benefits
Past benefits and evolutionary history
Why not all current traits are adaptations:
- The trait evolved under conditions that no longer exist, but persists because insufficient time or the absence of appropriate mutations prevented the replacement of the now non-adaptive trait. Some arctic moths fly in regions where bats are absent, but still cease locomotion upon exposure to an experimental ultrasonic stimulus.
- The trait develops as a maladaptive side effect of an otherwise adaptive proximate mechanism - that is, one that generally causes and adaptive outcome. Female rodents living in a communal nest may sometimes give milk to offspring other than their own as a by-product of their strong parental drive, which usually results in adaptive care of their own genetic offspring.
- The trait is expressed as a maladaptive consequence of a very recent change in the environment. Certain beetles attempt to copulate with discarded beer bottles.
- Arctic ground squirrels live where snakes do not, but when they are experimentally exposed to snakes, they show some of the same responses as other ground squirrels whose ranges overlap with dangerous predatory snakes
- A strong, generally adaptive drive to care preferentially for genetic offspring may lead some human stepparents to engage in criminal child abuse that seems certain to reduce the fitness of the child abuser
- Sea turtles sometimes die as a result of eating plastic bags, which resemble jellyfish sufficiently to trigger a feeding response. In the past, that response would have led to the adaptive ingestion of jellyfish, not the potentially lethal consumption of plastic debris
Current benefits of mobbing
Nesting gulls mob intruders but this is risky for gulls (injury or death). Prediction: if mobbing is behavioural adaptation against egg predators, then mobbing should reduce egg predation. Kruuk 1964.
Mobbing Increases Reproductive Success
Inside colony especially, probability that crow will be subject more attacks, but attempts become less successful
Comparative method, need a phylogeny
Testing evolutionary hypotheses, by comparing different taxa to see who does what, and correlating the occurrence of traits with the benefit of the trait
e.g. if ground predator mobbing is not needed or not beneficial it will not occur. no mobbing in cliff nesting kittiwakes for ground predators.
Cliff nesting behaviour is derived
Comparative method shows
where species demonstrate convergent and divergent evolution with shared ancestry and distinct ancestry.
Alcock’s 4 hypotheses for antipredator behaviours
Anti-detection/attack/capture/consumption
Anti-detection: crypsis: camouflage, transparency, nocturnality, subterranean living
Anti-attack: stotting in springbok, selfish herding, mimicry and warning colouration
Anti-capture: vigilance, speed, body part autotomy
Anti-consumption: fighting back, feigning death, releasing noxious chemicals, being hard to swallow
Camouflage may involve any of the other senses, not just vision
Either prey and/or predator may be camouflaged
Testing whether camouflage works
Pietrewicz and Kamil trained captive blue-jays to respond to white underwing moths. The behaviour of the moths (i.e. where they settle) affects the ability of the birds to detect them
Behaviour & camouflage: Decorator crab
Juvenile crabs preferentially decorate with Dictyota menstrualis
Prediction: crabs decorated with these alga will be less likely to be killed by predatory fish than crabs not using this alga
Result: crabs without this alga disappeared 5 times faster than those with
The alga contains a chemical that repels omnivorous fish
Stotting by Thomson’s Gazelles
when they spot a predator they stot.
Why advertise yourself to a predator? It says ‘I’ve seen you and I’m ready to flee’. it’s an honest signal. Even solitary animals stot so it’s not an alarm or social behaviour.
Stotting is a quality indicator as a smaller proportion of stotters vs. non-sotters are chase and predators failed to kill stotters
The Selfish Herd
Hamilton 1971. Prey dilution vs. conspicuousness.
Selfish herding affects positioning behaviour. Bluegill sunfish prefer to nest in the centre of groups where they are safer from egg predators.
Selfish herding in whirligig beetles. Larger groups are more attractive to predators, but the predation rate per individual is lower. Food-deprived beetles will position at edge of group to obtain food. Trade-off with resource and predation risk.
