Lecture 5: Avoiding Predation

Question 1

what is an adaptation?

Answer 1

a heritable trait that enhances the fitness of it bearers

-through current benefits, or past benefits & evolutionary history

Question 2

is every factor that reduces predation an adaption against predation?

Answer 2

NO

Question 3

current benefits of Mobbing: Kruuk 1964

Answer 3

• 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

Question 4

when would you use the comparative method?

Answer 4

when an experiment can’t be used

-way of comparing evolutionary hypothesis by comparing different taxa

Question 5

e,g, of using a comparitive method: Mobbing

Answer 5

• 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

Question 6

to use comparative method you need a strong

Answer 6

phylogeny method

Question 7

antipredator adaptations 4 groups:

Answer 7

• Anti-detection
• Anti-attack
• Anti-capture
• Anti-consumption

Question 8

anti detection example

Answer 8

Crypsis, e.g. camouflage, transparency, nocturnally, subterranean living

Question 9

anti Attack examples

Answer 9

-stotting in Springbok, selfish herding, mimicry and warning colouration

Question 10

anti capture examples:

Answer 10

Vigilance, run, swim or fly fast, body part autotomy (tail loss in lizards)

Question 11

anti-consumption adaptations

Answer 11

fighting back, feigning death, releasing noxious chemicals, being hard to swallow (e.g. inflation by puffer fish)

Question 12

camouflage: Peppered moth

Answer 12

• makes peppered moth less detectable to predators
• 2 subspecies; light form and melanic form
• larvae also camouflaged = dead twig

Question 13

camouflage points to remember:

Answer 13

1) camouflage may involve any of the sense, not just vision

2) either (or both) prey / predator may be camouflaged

Question 14

Testing whether camouflage words: Pietrewicz and Kamil

Answer 14

-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

Question 15

Behaviour & camouflage: Decorator crab

Answer 15

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

Question 16

Stotting by Thomson’s Gazelles

Answer 16

• 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’

Question 17

Stotting by Thomson’s Gazelles: “Ive seen you and am ready to flee” is known as the what hypothesis

Answer 17

Unprofitability hypothesis == the likely hypothesis

Question 18

Stotting by Thomson’s Gazelles: Anti ambush hypothesis

Answer 18

stating lets gazelles see what is ahead and reduces the chances they will be ambushed
–> but stotting occurs in all habitats including short grass

Question 19

Stotting by Thomson’s Gazelles: Alarm signal hypothesis

Answer 19

sotting warns conspecifics, especially offspring that predator is near
–> but even solitary animals Stot

Question 20

Stotting by Thomson’s Gazelles: Social cohesion hypothesis

Answer 20

stotting enables gazelles to form groups & flee in a coordinated manner
-but solitary animals stot

Question 21

Stotting by Thomson’s Gazelles: confusion effect hypothesis

Answer 21

• stotting confuses and distracts a predator preventing it focusing on one animal
• but solitary animals stot

Question 22

Stotting by Thomson’s Gazelles: is it an indicator of quality?

Answer 22

YES, lower proportion of stotters, than non stotters chased & predators fail to kill stotters
-honest signal of animals health

Question 23

The selfish herd: Snake in pond where safest place for frog to sit

Answer 23

• 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)

Question 24

selfish herd is an example of

Answer 24

Game theory

Question 25

selfish herding affects ___ behaviour

Answer 25

positioning

-Bluegill sunfish prefer to nest in the centre of groups where they are safer from egg predators

Question 26

selfish herding works through mechanisms known as

Answer 26

dilution effect

–larger the group, lower individuals chances of being eaten

Question 27

selfish herding in Whirligig Beetles

Answer 27

• sits on surface on pond, eats small insects
• predated by fish that come up from below
• larger groups more attractive to predators
• BUT larger groups the predation rate for each individual is less

Question 28

Whirligig beetles trade off :

Answer 28

• Food & predation risk

- -food more abundant on outside of group but predation risk greater

Question 29

Mayfly Emergence: Dilution effect (in time)

Answer 29

-nymphs = aquatic
-adults = aerial
predation risk is lower when many adults emerge as predators become satiated –> dilution effect, leading to synchrony of emergence

Question 30

Similarity between: Gamete release in coral & Sea-bird egg laying

Answer 30

SYNCHRONY to benefit from dilution effect –> satiate predators preying on gametes/chicks

Question 31

Group formation / vigilance

Answer 31

-Group formation may reduce predator attack/success via greater vigilance. If one individual in a group sees a predator it can warn the rest, or the others can see its escape behaviour.

Question 32

Can grouping be costly?

Answer 32

--increased food competition 
Sparrows; may feed alone/group 
-"chirrup" calls signal to form a group 
-predation risk = low = solitary 
-predation risk = high = group