Readings

Mills 142-153

Interspecific interactions

Interactions come in many different forms

Interspecific interactions

Interactions come in many different forms

Predation

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Evolution of behavior, morphology, physiology

Predation

Important, widespread effects on:

• Community structure
  • Picky predators can promote coexistence among competing prey species when the dominant competitor is the preferred prey (i.e. ‘competitive exclusion’ is prevented by predator)

Predation

Important, widespread effects on:

• Community structure
  • Picky predators can promote coexistence among competing prey species when the dominant competitor is the preferred prey (i.e. ‘competitive exclusion’ is prevented by predator)

Predation

Important, widespread effects on:

• Community structure

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

Yes

• Introduced rats, mongoose, and cats have caused the extinction of at least 43 bird species

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

Yes

• Invasive brown tree snakes caused the extinction of 10 bird species on the island of Guam

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

Yes

• Mesopredator release

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

Maybe?

Predation

Important, widespread effects on:

• Regulation of abundance and population dynamics of both predator and prey

Do predators control the abundance of their prey?

• On Island Royale, wolf/moose populations are linked but also influenced by vegetation and winter severity

How do predators impact prey population?

Predation rate $(\large P)$

Percentage of prey population killed per unit time

$$\large P = \frac{\#\; prey\; killed}{Prey\; abundance} \times 100$$

How do predators impact prey population?

Predation rate $(\large P)$

Percentage of prey population killed per unit time

$$\large P = \frac{\#\; prey\; killed}{Prey\; abundance} \times 100$$

• Number of prey killed = numerical response $\times$ functional response

Numerical response

Change in number of predators as prey abundance changes

• Number of predators present at a given prey density

Numerical response

Change in number of predators as prey abundance changes

• Number of predators present at a given prey density
• Function of how prey influence $B$ $D$ of predator

Numerical response

Change in number of predators as prey abundance changes

• Number of predators present at a given prey density

• Function of how prey influence $B$ $D$ of predator

• Predators may also congregate at prey source: aggregative response

Numerical response

When introduced prey lead to large numerical response of predators, native prey can suffer

• high abundance of predators leads to unsustainable predation on native prey

• hyperpredation

Functional response

Also known as the kill rate

number of prey killed per predator per unit of time

• as number of prey increases, kills rate should change
  • search time
  • handling time
  • satiation

Functional response

Also known as the kill rate

number of prey killed per predator per unit of time

• as number of prey increases, kills rate should change
  • search time
  • handling time
  • satiation

Type II

Functional response

Also known as the kill rate

number of prey killed per predator per unit of time

• as number of prey increases, kills rate should change
  • search time
  • handling time
  • satiation

Type III

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Total predation rate

$$\large P = \frac{Numerical\;response \times\;functional\;response}{Prey\; abundance} \times 100$$

Predation

Other considerations

• Is increased predation compensated by higher fecundity?

• Which individuals are killed?

• Human dimensions