Avoiding Predation

Question 1

Antipredator behaviour: example of adaptive behaviour

Answer 1

Detection avoidance
Attack avoidance behaviour
Selfish herding

Question 2

What is an adaptation?

Answer 2

Heritable trait that enhances the fitness of its bearers

Current benefits
Past benefits and evolutionary history

Question 3

Why not all current traits are adaptations:

1. 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.
2. 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.
3. 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.

Answer 3

1. 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
2. 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
3. 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

Question 4

Current benefits of mobbing

Answer 4

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.

Question 5

Mobbing Increases Reproductive Success

Answer 5

Inside colony especially, probability that crow will be subject more attacks, but attempts become less successful

Question 6

Comparative method, need a phylogeny

Answer 6

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

Question 7

Comparative method shows

Answer 7

where species demonstrate convergent and divergent evolution with shared ancestry and distinct ancestry.

Question 8

Alcock’s 4 hypotheses for antipredator behaviours

Answer 8

Anti-detection/attack/capture/consumption

Question 9

Anti-detection: crypsis: camouflage, transparency, nocturnality, subterranean living

Answer 9

Anti-attack: stotting in springbok, selfish herding, mimicry and warning colouration

Question 10

Anti-capture: vigilance, speed, body part autotomy

Answer 10

Anti-consumption: fighting back, feigning death, releasing noxious chemicals, being hard to swallow

Question 11

Camouflage may involve any of the other senses, not just vision

Answer 11

Either prey and/or predator may be camouflaged

Question 12

Testing whether camouflage works

Answer 12

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

Question 13

Behaviour & camouflage: Decorator crab

Answer 13

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

Question 14

Stotting by Thomson’s Gazelles

Answer 14

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

Question 15

The Selfish Herd

Answer 15

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.

Question 16

Mayfly emergence

Answer 16

dilution effect.

Predation risk is lower when many adults emerge as their predators become satiated after eating a lower proportion of mayfly. This leads to synchrony of emergence i.e. selfish herding in time

Question 17

Group formation and vigilance

Answer 17

group formation may reduce predator attack/success via greater vigilance. Kenward 1978. Individuals react quicker to a threat in a group than as individual. Reaction distance is greater and total attack success declines in larger flocks!

Question 18

Vigilance in sparrows

Answer 18

grouping can be costly e.g. increased food competition.

Sparrows may feed alone or in groups. Prediction: when predation risk is low - solitary
when predation risk is high - group

sparrows “chirrup” to attract others to them

Fewer chirrups were made when birds foraged closer to safe cover and far from predator