Ecological footprints of some nations already exceed available ecological capacity.

Our ecological ‘footprint’…1)

Before lecture on Tuesday,

take the quiz on www.myfootprint.org.

Insert your result in the top of the lecture outline, as shown on the LO (cut out the one shown), and bring the lecture outline to class.

Chapter 15: Dynamics of predator-prey interactions

Objectives• Adaptations of predators• Prey deterrents to predation• Do predators limit prey?

• Functional / numerical responses of predators to prey density

• Predator-prey synchronized cycles• How stabilize predator-prey interactions?• Laboratory studies of refugia/spatial heterogeneity

x

What are predator adaptations to exploit prey?

The jaws of snakes are adapted for grasping and swallowing large prey.

Predators vary in size relative to their prey.

Prey deterrents to predation

• Group living

• Induced structural defense

• Chemical defense

• Cryptic coloration

• Aposematism

• Mimicry

Prey have active adaptations for escaping their predators: chemical warfare!

Palatable prey avoid predators passively via crypsis.

Cryptic coloration - passive escape

Unpalatable animals have warning coloration (aposematism). Predators learn from mistakes.

Figure 3

Warning is even greater in groups…

Top-down control Tri-trophic predators interactions

herbivores (prey)

plants

nutrients/light Bottom-up control

Do predators control prey abundance?If…then…

Figure 6

Is there a response of this predator to an increase in its prey? Why or why not?

territorial Heavyseed crop in 89

Figure 7

Human activities have altered:1) predator-prey relations2) ‘top-down’ control

Individual predators exhibit 3 types of functional responses to increasing prey density.

Functional response: A change in rate of capture of prey by an individual predator as prey density changes.• Type I: Capture directly proportional

to prey density

• Type II: Capture levels off at high prey

density (predator satiation)

• Type III: as Type II, but is also low at low

prey density

• 1) heterogeneous habitat---> hiding places

• 2) lack of learned search behavior

• 3) switching to alternative prey

***What type of functional response of kestrels to vole density?

***What type of functional response of wolves to moose?

***What type of functional response?Predators switch to different prey in responseto fluctuations in prey density.

Switching to alternative prey occurs only when preferred prey density falls to low level.

Is this a numerical or functional response of wolves to moose?

Figure 11

Why didn’t top-down control limit spruce budworm devastation?

***Is there a functional response? Numerical response? What is the total response of warblers to spruce budworm abundance? Does the warbler control its prey?

Figure 12A B C

Population cycles synchronized among species in a region. Periodic cycles with peaks separated by same number of years.

Figure 13

Cycles have damped out with warmer temperatures.

Other species may vary in their response to changes in the environment --> asynchronized cycles.

Figure 14

Predator and prey populations often increase and decrease in synchronized cycles. Which group lags the other?

• Predators eat prey--->reduce prey numbers• Predators go hungry---> their numbers drop• Few prey do better--->prey numbers rise• Predators have more food---> their numbers rise.

• Do prey control predators or vice versa?• What other factor could explain prey cycles?

Question: What factors control the hare-lynx population cycle?

• Hypothesis: Predation, food availability to prey, or a combination of those two factors controls the cycle.

• Null Hypothesis: They do NOT control the cycle.

• Experimental Design??• Prediction: Hare populations in at least one

type of manipulated plot will be higher than mean population in control plots.

• Prediction of null H: Hare populations will be the same in all of the plots. Figure 16

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

ControlsFence;no lynx

Extra food

for hares Both

• What is conclusion?

• Do predation, food, or a combination of both factors control the hare-lynx cycle?

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Figure 17

The lynx-hare story update…alternative explanations.

Fluctuations in population density in a host-parasitoid system in the lab.

How stabilize predator-prey interactions?

No sediment

Sediment(hiding places)

Immigration

Figure 19

Huffaker’s experiment to get predator-preypopulations to persist without immigration.

1) Oranges clumped---> what happened to cycle?

Figure 20

2) Oranges dispersed randomly--->what happened to cycles? Why?

3) Spatial heterogeneity --->stable cycles.

Figure 21