lecture 11: Organisms & Predation

Question 1

Do predators reduce prey populations?

Answer 1

General pattern: prey N is lower in the presence vs. absence of predators

Question 2

Hudson Bay Company example:

Answer 2

yearly data on the number of lynx and hare furs harvested by trappers
* Large, regular cycles ~ 10 years
* N of predator & prey species are highly synchronized
* predator N trails prey N by 1-2 years

predator is always behind by prey population by a few years with prey ahread to avoid extinction

Question 3

Lotka Volterra Models and symbols

Answer 3

for understanding predator-prey
population oscillations

P= predator population size
H= prey population size
p= efficiency of the predator to capture prey
a = efficiency of the predator to convert the prey consumed into offspring

Question 4

population sizes of predators and prey are linked through

Answer 4

the density-dependent influences each species has on the other’s birth and death rates
– Prey – death rates influenced by the size of the predator population
and vice versa

Question 5

Functional Response=

Answer 5

the relationship between prey density and predator
consumption rate

Consumption rate of a predator depends on the density of prey

Question 6

Numerical Response=

Answer 6

The increase in predator reproduction due to increased prey consumption.

Question 7

Isocline=

Answer 7

line of no growth of prey or predator population

These dynamics create oscillating predator-prey populations…
Predict: stable oscillations of predator and prey populations

Question 8

co-evolution

Answer 8

Predators act as a selective pressure on prey species and vice versa

– prey traits that reduce chances of being detected and captured by
predators will increase fitness

Natural selection will result in ‘smarter’, more evasive prey
Failure to capture prey results in reduced fitness of predators

vice versa

predator and prey are in an arms race

Question 9

Prey adaptations

Answer 9

1) Detect Predators
2) Avoid Being Seen
3) Prevent Attack
4) Escape Once Attacked

Question 10

Predator adaptations

Answer 10

Predators
Cryptic Colouration
Mimicry
Stalking/Ambush
Prey Detection
Poison Resistance
Social Hunting Groups

Question 11

What does the Lotka-Volterra predator-prey model describe?

Answer 11

Non-linear growth and oscillations in predator and prey populations based on density-dependent interactions