Nature of Predation - Lecture 7

Question 1

Define: Predation

Answer 1

“Consumption of one organism (the prey) by another organism (the predator) when the prey is alive when it is first attacked by the predator.

Question 2

Define: Omnivore

Answer 2

An organism that consume prey from more than one trophic level, e.g. plants and herbivores, or herbivores and carnivores.

Question 3

What is the functional classification of a true predator?

Answer 3

• Kill prey more or less immediately after attacking them.
• Kill several or many different prey individuals during their lifetime.
• Often entirely consume prey.
  ie. Lion, Bear, Venus fly trap

Question 4

What is the functional classification of a grazer?

Answer 4

• Also attack large numbers of prey in their lifetime
• Remove only part of each prey individual.
• Effect on prey individual, although typically harmful, rarely lethal in the short term.
  ie. Buffalo, cows, mosquito (ignoring disease transmission)

Question 5

What is the functional classification of a parasite?

Answer 5

• Consume “part” of their prey, typically harmful but rarely lethal in the short term.
• Attacks concentrated on one or very few individuals in their life.
• intimate associations between parasites and their prey (hosts); not seen in true predators or grazers.

Question 6

What is the functional classification of a parasitoid?

Answer 6

• Mainly insects.
• Free living adults, but eggs are laid in(or near) other insects.
• Immature larvae live in/on host eventually killing and consuming all of it.
• an adult parasitoid emerges from what is apparently a developing host.

Question 7

Parasitoids straddle other categories, which and how?

Answer 7

• True predators: eventual lethality
• Grazers: do not cause immediate death of host
• Parasites: intimately associated with host.

Question 8

What effect do true predators have on prey fitness and abundance?

Answer 8

Immediate effects, rapid death.

Question 9

What effects do grazers and parasites have on prey fitness and abundance?

Answer 9

Profound, but more subtle effects. Although they don’t kill prey immediately, they make the prey more susceptible to other mortality factors.

Question 10

What is the overall effect true predators, grazers and parasites all have on their prey?

Answer 10

They all obtain resources from prey, reducing either individual fecundity or probability of individual survival and thus reduce prey abundance.

Question 11

How can plants compensate for herbivory?

Answer 11

By producing defensive structures or chemicals.

Question 12

What response does field gentian have to herbivory?

Answer 12

• Removal of of leaves may decrease shading and increase photosynthesis in remaining leaves.
• Plants may compensate using stored reserves.
• Root: shoot balance maintained by transferring production to damaged parts.

Question 13

What are some ways animals can avoid detection, selection and capture by predators?

Answer 13

• Chemical defences
• Cryptic colouration
• Object resemblance
• Protective armour
• Behavioural defences, such as alarm calls, and grouping.

Question 14

What is apsematism?

Answer 14

Warning colouration, advertising of distastefulness. Predators must experience unpleasant taste/toxicity of these animals before learning to avoid them.

Question 15

What is batesian mimicry?

Answer 15

An edible species that resembles an inedible species in the same habitat.

Question 16

What is Müllerian mimicry?

Answer 16

Unpalatable or venomous species share similar colour patterns, the predator only has to be exposed to one species before learning to stay away from similarly coloured species.

Question 17

What is a mast year?

Answer 17

A year in which there is synchronous production of a large volume of seed, often across a large geographical area. An amount larger than can be consumed by predators to ensure survival.

Question 18

What is non-random prey selection?

Answer 18

• Predator may focus on old, young, or sick individuals.

Question 19

What is the optimal foraging theory?

Answer 19

That predators maximise overall rate of energy intake.

Question 20

According to the optimal foraging theory what should be a generalist?

Answer 20

Predators with short handling times relative to search times. i.e. Insectivorous birds.

Question 21

According to the optimal foraging theory what should be a specialist?

Answer 21

Predators with long handling time relative to search times. i.e. lions (specialise on immature, lame, old prey.)q

Question 22

According to the optimal foraging theory what should have a broader diet?

Answer 22

In an unproductive environment a predator should have a broader diet than in a more productive environment, for example bears feeding on salmon, when there are high prey densities only eat the nutritionally rich body parts.