lecture 8

Question 1

Individuals do not live in isolation…

Answer 1

• Individuals of the same species have similar requirements for survival, growth, reproduction
• demand for resource may exceed supply
• individuals may compete for resources…

Question 2

Intraspecific Competition

Answer 2

= an interaction between individuals of the same species (intra) brought about by a
shared requirement for a resource in limited supply

Question 3

Intraspecific Competition-

– Results in:

Answer 3

• Reduced survival, growth, and/or reproduction of some individuals
– possible reduction in fitness Competition acts as a selective pressure in nature

Question 4

How does competition arise?

Answer 4

• Resources are not evenly distributed (distributed in patches)
• Aggregative Response
• competitive interactions

Question 5

Aggregative Response

Answer 5

predators concentrate where prey density is high

o due to high consumption rates

Question 6

Competitive Interactions

Answer 6

• can lower consumption rates

- patch with highest prey density is not always the best!

Question 7

Types of Competition

Answer 7

1. Exploitation (Scramble) Competition

2. Interference (Contest) Competition

Question 8

• Exploitation (Scramble) Competition

Answer 8

– an individual responds to a decreased level of a limited resource remaining after it has been
exploited by other individuals
– individuals donotinteractdirectly

Question 9

• Interference (Contest) Competition

Answer 9

– an individual actually prevents another from exploiting a limited resource within a portion
of the habitat
– individuals interactdirectly

Question 10

Intraspecific Competition What is the result of Competition?

Answer 10

net energy gain - energy loss ↑ +/or energy gain ↓ due to competitive interactions
-Consumption rates decrease with increasing numbers of competitors

Question 11

Low competition

Answer 11

Reduced Growth

Question 12

Moderate competition

Answer 12

Reduced Growth, Reproduction

Question 13

High competition

Answer 13

Reduced Growth, Reproduction & survival

Question 14

How do individuals balance the attraction to patches of high prey abundance and the repulsion by the presence of competitors?

Answer 14

Use Behavioural Ecology to study how an individual’s behaviour is adapted to it’s environment

Question 15

Ideal Free Distribution Model Assumptions:

Answer 15

1. There are a number of prey patches that vary in quality
2. Competitors are ‘free’ to exploit all patches (can move ‘freely’ among
   patches)
3. Individual prey consumption rates decline with increasing numbers of
   competitors in the patch increases
4. Individuals have equal competitive abilities
5. Animals distribute themselves ‘ideally’ among patches to obtain highest
   consumption rates (maximize net energy gain to ensure high fitness)

Question 16

As competition ^ in high quality patch

Answer 16

the patch quality v (leading to lower consumption rates)

Question 17

•

Individuals in an area reach an equilibrium distribution, where:

Answer 17

• all patches occupied

* more individuals in higher quality patches…

Question 18

At the equilibrium distribution…

Answer 18

the consumption rates of individuals are equal for all competitors in all patches

Question 19

Can be a dynamic equilibrium

Answer 19

– individuals are constantly moving among the available patches
… but individuals in the lowest quality patch will not gain access to more prey if they move to a higher quality patch

Question 20

Generalized Experimental Design:

Answer 20

• Prey arrives in the patch at a particular rate
• Prey is consumed immediately
• Scramble/Exploitation Competition -competitors do not interact directly

Question 21

Example – Harper 1982

Answer 21

Ducks on a lake with two feeding stations (station A and B)
• pre-cut, weighed bread pieces
• identify individual ducks
• same input rate at A and B
• PREDICTED IFD

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