Animal Behaviour- Predator-prey interactions

Question 1

What is meant by the evolutionary arms race?

Answer 1

When each side keep developing strategies to overcome the other one’s (predators select for foraging improvements whilst prey select for defence improvements- Red Queen hypothesis)

Question 2

Why is it that individuals do not get better (fitness wise) in the Red Queen hypothesis?

Answer 2

Because the opponent/predator/prey is also getting better so they essentially stay in the same place (fitness wise)

Question 3

Using the example of the insects and bats, how have they both evolved adaptations to help them survive?

Answer 3

Bats use echolocation to locate moths, moths have evolved tympanic ears on many parts of their bodies. Tympanic ears have evolved 8 times and in 6 orders so must be to avoid predation (not just by chance)

Question 4

What are two aims of camouflaging?

Answer 4

Either to avoid detection by predator (Crypsis) in the first place or avoid recognition by predator of being food

Question 5

Name three strategies of crypsis (avoiding detection by predator).

Answer 5

Background matching
Countershading
Disruptive colouration (breaks up your outline)

Question 6

What was the experiment that proved that background matching was an adaptation to predators?

Answer 6

Blue jays responded to whether they could see a moth on a background (by pecking screen) or not (by pecking black area next to screen). They were very bad at detecting moths on a cryptic background

Question 7

Describe the experiment with Great tits that proved even a tiny bit of crypsis gave an individual a selective advantage when it was not common.

Answer 7

A conveyor belt with three items was run past a great tit and it had to choose whether to eat them or wait for the next thing. The three items were: Inedible twigs, large cryptic prey (meal worm in opaque straw) or small conspicuous prey (half mealworm in transparent straw). There were two conditions; A which had the twigs as more common and B in which the large prey was more common (small prey remained constant). In condition A, they chose the small conspicuous prey a lot. In B, small prey were left alone much more and the birds worked out the cryptic prey

Question 8

What is countershading?

Answer 8

Type of camouflage used by birds, fish, gazelles. It enables the animals to be less easily seen as they fit in their environment more. Counter shading stops under shadowing showing. Animals are often darker on top so that when light shines on them (sun), they appear ‘invisible’ to colour blind animals as no under shadow is produced

Question 9

How was counter shading proven to be an effective camouflage using caterpillars?

Answer 9

Fake caterpillars were put out and it was recorded how many of each type (some did not have counter shading and some did) were eaten by birds. It was found that those with the adaptations were significantly less targeted. The reversal of colours was tested to see if birds were just avoiding eating them due to two colours but these were eaten even more than control so proved it was counter shading that worked

Question 10

What is disruptive colouration and why is it beneficial for animals?

Answer 10

When animals have different colours to break up their body plans. Fish use this to avoid having a fish like shape on backgrounds. Same with moths who survived much longer when they had spots on the edge of their wings rather than block colours or even spots in the centre of wings

Question 11

The other type of camouflage from crypsis is preventing recognition. Prey polymorphism is a type of this. Explain why it may be beneficial for spss such as the grouse locusts to have this.

Answer 11

If each individual in a spss is varied then it may be hard to tell whether they are from an edible spss by the predator

Question 12

What is apostatic selection?

Answer 12

Apostatic selection is frequency-dependent selection by predators. It applies when prey are two or more forms (morphs) which look quite different

Question 13

When looking at predators who prey on a species with two morph types, what does it mean if p12 is above 1? what about if it is below 1?

Answer 13

This all applies if there are two morphs in a species e.g seagull and two morphs of crabs)
If it is above one, it means the predator prefers to eat morph 1 over morph 2
If it is below, it means the predator prefers to eat morph 2 over morph 1

Question 14

In some species, what happens when p drops below 1?

Answer 14

The predator sometimes swaps preferences to the rare type (may be easier to spot amongst the common types)
but can also be the other way around

Question 15

How can frequency dependent apostatic selection be good for the prey?

Answer 15

When the predator swaps to the common type when p drops below 1, this allows survival of both morphs

Question 16

Why is it thought that as a prey item becomes more common, the predator switches its preference?

Answer 16

As it becomes more common, the predator can learn what they look like and form the search image, therefore making it easier to spot (aka perceptual switching)

Question 17

What is masquerading?

Answer 17

When an animal does not really avoid detection but rather masquerades as an inedible object (e.g a leaf)

Question 18

What did an experiment with chicks find about thorn moths and masquerading?

Answer 18

That if the caterpillars of the moths (which look like sticks) go onto a stick with small thorns, it was very easy to spot them. Given the choice, most of the caterpillars decided to go on plants with thorns that were similar to their body size which suggests this is an adaptation for avoiding recognition by predators

Question 19

Aposematic signals are those which suggest the animal is toxic to eat. What was found about how obvious the colouration was to predators?

Answer 19

It was found that more obvious colours were more protective. When placed on a green background, blue coloured prey were eaten at first along with green but it was found more quickly that blue were toxic so fewer were eaten altogether (both green and blue=toxic). On a Blue background, green were discovered to be toxic more quickly. This proves that being an obvious colour is better

Question 20

Aposematic signals seem to be no use if the predator has to eat you to find out you’re poisonous. What is the argument for why it occurs then?

Answer 20

Could be that you look like kin and so they won’t eat your family after eating you/ works through kin selection

Seen that family groups tend to use this over crypsis whereas solitary animals use crypsis

In extreme examples, desert locusts become aposematic in gregarious situations (so further prove they are linked)

There are many factors that suggest this is not the case though (phylogenetic trees suggest that the aposematic colour evolved before gregariousness)

Question 21

What is mullerian mimicry?

Answer 21

When animals share similar looks (mimicry ring) to show certain traits- secondary defences such as poison

Mutualistic relationship as both have benefits of looking like each other but costs of predator attacks

e.g= butterflies, bumble bees

Question 22

What is batesian mimicry?

Answer 22

Animals that get the benefits of looking like another without paying the costs e.g coral snakes which do and king snakes that don’t produce toxins

Imperfect mimicry still works!

Question 23

What are diematic displays (comes from greek ‘to frighten’)?

Answer 23

Displays which are sudden. The onset is triggered by a predator attack- tend to be a last attempt for those which are normally camouflaged

Question 24

How did Steven et al. prove that eye spots on animals such as caterpillars and butterflies were not meant to mimic their predators eyes and were just there to startle?

Answer 24

Using cardboard cut outs, it was found that those with shapes on were attacked less than blank/plain ones however the shape of the spots didn’t make a difference

Question 25

Fish C-starts are an escaping behaviour of fish triggered by water movement. They face the head towards a direction and then swim. How have tentacled snakes taken advantage of this behaviour?

Answer 25

Tentacled snakes are their predators. They position themselves surrounding the fish and then tense neck muscles so that when the fish swims it swims straight into the snakes mouth. The snake really manipulates the response- not by chance that the fish swims towards the snakes head

Question 26

Why doesn’t the fish stop doing the c-start response if the predator can catch it?

Answer 26

There is a trade-off between this predator escape and all others. Seeing as the tentacle snake is rare, it is worth the trade-off

Question 27

What sort of trade-offs may need to be made in prey defence?

Answer 27

Allocation - energy allocated to certain things other than defences
Opportunity - e.g cryptic animals have limited habitats

Question 28

What is the trade-off that the freshwater snail makes for its retreat defence?

Answer 28

Expels blood, when taking up water from surroundings to replace the fluid, it risks taking up parasites