Predator and Prey behaviours

Question 1

How long will an animal forage for?

Answer 1

Marginal value theorem (Charnov 1976) predicts that the predator will stay in the current patch until its rate of food intake drops to a level that is equal to the rest of the environment
If travel time to patches increases optimal time to stay in patch also increases

Question 2

How do animals choose what to eat?

Answer 2

Prey variations - size, agility, nutritional value, toxicity etc
Choice based on energy maximisation - costs vs benefits
Charnov’s optimal diet model shows three key predicitons
- A predator will always take the most profitable prey
- it will ignore less profitable prey according to unequal gains
- whether or not less profitable prey is included is independent of its encounter rate

Question 3

What are the 5 types of antipredatory behaviour?

Answer 3

Avoidance
Withdrawal
Flight
Diversion
Deterrance

Question 4

Describe a sturdy on crypsis

Answer 4

Crypsis - avoiding observation or detection
Feltmate and Williams (1989) - stone fly nymphs exposed to rainbow trout - nymphs in the dark 3/24 were eaten while in the light 19/24 were eaten

Question 5

Describe an experiment on withdrawal

Answer 5

Barnard (1980) - house sparrows use hedgerows as cover

• fly out feed and fly back moving up and down hedgerows
• risks attack from aerial predators
• the further away the birds are to the hedgerows the less time they spend foraging

Question 6

Why is flight behaviour costly?

Answer 6

Errtic, unpredictable and zig zag behaviours make the actions energy expensive

Question 7

Where do animals choose to forage?

Answer 7

Natural food sources seldom distributed evenly
Prey often clump - result of resources, social interactions
Predators choose patches in which it will gain the highest net return for its feeding efficiency
Predators sample different patches