EE Lecture 29: Predation 1

Question 1

what are the main types of predators

Answer 1

true predators - consume many prey
grazers - consume only part of their prey, but attack many
parasitoids-free living adult insects, lay eggs inside of host
parasites - consume parts of hosts, but typically one host per life time

Question 2

what is a true predator

Answer 2

low intimacy, high lethality - org consume WHOLE prey and many prey in their life

Question 3

what are grazers

Answer 3

org consume only part of their prey, but attack many

Question 4

what are parasitoids

Answer 4

free living adult insects-lay eggs inside hosts

Question 5

what are parasites

Answer 5

predators that consume parts of host,but typically one host per lifetime

Question 6

how much % are parasitoids of all species

Answer 6

`10% of all species are parasitoids

Question 7

when does functional response decline

Answer 7

when demand of prey exceeds supply

Question 8

whats on the axes of a functional response graph

Answer 8

x - prey available

y - prey eaten per predator

Question 9

what is a functional response

Answer 9

relationship between prey eaten and prey available

Question 10

give an example of a predator prey cycle

Answer 10

snowshoe hare cycle - popns increased and decreased regularly
their predators were lynxs
abundancies every 10 yrs
food can be limiting at peak hare densities,
lynx and coyotes kill more hares per day during the peak and decline phases of the hare cycle than during the increase phase
after predator numbers plummet
physical condns of hares worsens as hares decrease in numbers

Question 11

what are main “anomalies” of hare-lynx popn cycles

Answer 11

1. why hare BRs drop during the decline phase of the cycle
2. why hare numbers sometimes rebound slowly after predator numbers plummet
3. why the physical condns of hares decrease, when hare pops decrease

Question 12

what is masting

Answer 12

when some plants avoid herbivory by producing seeds some years and not othera

Question 13

how many functional responses are there

Answer 13

3
I - assumes a linear increase in intake rate with food density - suggests infinite appetite of predators
II - when type I satiates - saturating curve dependent on apetite
III - like II but low density line is more linear to account for the learning time&/prey switching

Question 14

what is the flaw of the type I functional response

for which predators does this not count

Answer 14

suggests infinite appetite of predators

ok for passive predators - eg. spiders with webs

Question 15

what is the type I functional response

Answer 15

infinite appetite of predators, constant positive correlation straight line through origin

Question 16

what is type II FR

Answer 16

type I but it satiates - characterised by decelerating intake rate follows from the asusmption that the consumer is limited by its capacity to process food

Question 17

why does the graph of type II FR satiate

Answer 17

because its dependent on predators appetite - counts for the fact that a predator is limited by its capacity to process food and search food

Question 18

what is type III FR

Answer 18

similar to type II in that high levels of prey density saturation occurs, but becomes SIGMOIDAL - like the logistic eqtn
@ low prey density levels, the graphical relnship of no. of prey consumed and the density of the prey pop is moer than linearly inc function - caused by LEARNING TIME &/ prey switching

Question 19

why is type III FR more linear

Answer 19

accounts for learning time &/ prey switching

Question 20

which FR type is a linear increase

Answer 20

type I

Question 21

which FR type is a linear increase which then levels off

Answer 21

type II

Question 22

which FR type is a sigmoidal shape

Answer 22

type III

Question 23

which FR type assumes infinite predator appectite

Answer 23

FR type I

Question 24

which FR type accounts for learning time&/ prey switching

Answer 24

Fr Type III

Question 25

which FR type accounts for saturation predator appetite

Answer 25

type II

Question 26

what is a functional type 2 response aka

Answer 26

inverse density dependence

Question 27

if you think of a FR type II as %prey as opposed to number, what graph do you get

Answer 27

inverse density dependence

Question 28

what does stability require

Answer 28

density dependence - a higher proportion of prey eaten at high densities rather than low

Question 29

what ways of stabilising a pop are there

Answer 29

density dependence aggregation numerical response

Question 30

what is a numerical response

Answer 30

a change in predator numbers in response to a change in prey numbers

Question 31

compare numerical and functional response

Answer 31

functional response shows relnship between prey no. and prey eaten whereas numerical is a change in predator numbers in response to a change in prey numbers

Question 32

give a common mechanism of numerical response

Answer 32

spatial aggragation

Question 33

what is spatial aggregation

Answer 33

predators move into regions with higher than average prey numbers predators emigrate from patches once prey numbers become depleted

Question 34

how do numerical responses act in the long term

Answer 34

act through changes in the predators birth and death rate more prey = higher predator birth rate more prey = low pred DR

Question 35

why will stability come from the predators numerical response and not the functional response

Answer 35

because the FR is inversely density dependent and hence destabilizing

Question 36

which is more destabilizing, FR or NR

Answer 36

FR is more destablizing because it is inversely density dependent and hence destabilizing

Question 37

which FR type is stabilizing

Answer 37

type 3

Question 38

when is a FR stabilzing

Answer 38

when switching between rpey species/behaviours that reduce the rate of predation become scarce (eg.loss of search image) this is in type 3

Question 39

which FR is Hollings?

Answer 39

type 3

Question 40

what models for popn dynamics are determined by NRs

Answer 40

nicholson bailey | lotka volterra

Question 41

what are the nicholson bailey models

Answer 41

Ht+1 = RHt * e^-aPt Pt+1 = cHt (1 - e ^ -aPt)

Question 42

in NB models -nicholson bailey models - what does Ht and Pt represent

Answer 42

density of host and parasitoid at year t

Question 43

in NB model, what is R

Answer 43

no. unparasitized host offspring surviving to next year

Question 44

what is e^-aPt representing in the NB model

Answer 44

represent the probability that host escapes random encounters

Question 45

what is (1- e^-aPt) representing in the NB model

Answer 45

the probabilty of the parasitoid parasitizing (being parasitized)

Question 46

what does a represent in NB model

Answer 46

a proportionality constant - search efficiency

Question 47

what does c represent in NB model

Answer 47

conversion rate of hosts into parasitoids

Question 48

why is NB model so unstable

Answer 48

any deviation @ all results in unstable dynamics as any data out of sync will crash the popn- but it does coincide with real data

Question 49

WHEN is it a good idea to use the NB model

Answer 49

when testing biological control for parasitoids because you want the popn of parasitoids to crash

Question 50

what is eqbm for NB model

Answer 50

H0 = R / (R - 1) * log(R)/ac | Po - log (R) / a

Question 51

H0 = R / (R - 1) * log(R)/ac Po - log (R) / a what do these show

Answer 51

show the inherent instability in NB, eqbm given by these eqts

Question 52

what is the drawback of aggregation

Answer 52

it is stbailizing but may increase host popn size | aggregation stabilizes by causing partial refugia

Question 53

what does direct inverse dependence mean (in terms of parasitoid/predators)

Answer 53

direct inverse dependence means that at high parasitoid densities, predators interact and interfere reducing effective attack rate