EE Lecture 29: Predation 1 Flashcards
what are the main types of predators
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
what is a true predator
low intimacy, high lethality - org consume WHOLE prey and many prey in their life
what are grazers
org consume only part of their prey, but attack many
what are parasitoids
free living adult insects-lay eggs inside hosts
what are parasites
predators that consume parts of host,but typically one host per lifetime
how much % are parasitoids of all species
`10% of all species are parasitoids
when does functional response decline
when demand of prey exceeds supply
whats on the axes of a functional response graph
x - prey available
y - prey eaten per predator
what is a functional response
relationship between prey eaten and prey available
give an example of a predator prey cycle
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
what are main “anomalies” of hare-lynx popn cycles
- why hare BRs drop during the decline phase of the cycle
- why hare numbers sometimes rebound slowly after predator numbers plummet
- why the physical condns of hares decrease, when hare pops decrease
what is masting
when some plants avoid herbivory by producing seeds some years and not othera
how many functional responses are there
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
what is the flaw of the type I functional response
for which predators does this not count
suggests infinite appetite of predators
ok for passive predators - eg. spiders with webs
what is the type I functional response
infinite appetite of predators, constant positive correlation straight line through origin
what is type II FR
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
why does the graph of type II FR satiate
because its dependent on predators appetite - counts for the fact that a predator is limited by its capacity to process food and search food
what is type III FR
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
why is type III FR more linear
accounts for learning time &/ prey switching
which FR type is a linear increase
type I
which FR type is a linear increase which then levels off
type II
which FR type is a sigmoidal shape
type III
which FR type assumes infinite predator appectite
FR type I
which FR type accounts for learning time&/ prey switching
Fr Type III
which FR type accounts for saturation predator appetite
type II
what is a functional type 2 response aka
inverse density dependence
if you think of a FR type II as %prey as opposed to number, what graph do you get
inverse density dependence
what does stability require
density dependence - a higher proportion of prey eaten at high densities rather than low
what ways of stabilising a pop are there
density dependence
aggregation
numerical response
what is a numerical response
a change in predator numbers in response to a change in prey numbers
compare numerical and functional response
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
give a common mechanism of numerical response
spatial aggragation
what is spatial aggregation
predators move into regions with higher than average prey numbers
predators emigrate from patches once prey numbers become depleted
how do numerical responses act in the long term
act through changes in the predators birth and death rate
more prey = higher predator birth rate
more prey = low pred DR
why will stability come from the predators numerical response and not the functional response
because the FR is inversely density dependent and hence destabilizing
which is more destabilizing, FR or NR
FR is more destablizing because it is inversely density dependent and hence destabilizing
which FR type is stabilizing
type 3
when is a FR stabilzing
when switching between rpey species/behaviours that reduce the rate of predation become scarce (eg.loss of search image)
this is in type 3
which FR is Hollings?
type 3
what models for popn dynamics are determined by NRs
nicholson bailey
lotka volterra
what are the nicholson bailey models
Ht+1 = RHt * e^-aPt
Pt+1 = cHt (1 - e ^ -aPt)
in NB models -nicholson bailey models - what does Ht and Pt represent
density of host and parasitoid at year t
in NB model, what is R
no. unparasitized host offspring surviving to next year
what is e^-aPt representing in the NB model
represent the probability that host escapes random encounters
what is (1- e^-aPt) representing in the NB model
the probabilty of the parasitoid parasitizing (being parasitized)
what does a represent in NB model
a proportionality constant - search efficiency
what does c represent in NB model
conversion rate of hosts into parasitoids
why is NB model so unstable
any deviation @ all results in unstable dynamics as any data out of sync will crash the popn- but it does coincide with real data
WHEN is it a good idea to use the NB model
when testing biological control for parasitoids because you want the popn of parasitoids to crash
what is eqbm for NB model
H0 = R / (R - 1) * log(R)/ac
Po - log (R) / a
H0 = R / (R - 1) * log(R)/ac
Po - log (R) / a
what do these show
show the inherent instability in NB, eqbm given by these eqts
what is the drawback of aggregation
it is stbailizing but may increase host popn size
aggregation stabilizes by causing partial refugia
what does direct inverse dependence mean (in terms of parasitoid/predators)
direct inverse dependence means that at high parasitoid densities, predators interact and interfere reducing effective attack rate
