L5 - Foraging

Question 1

What are the two key factors in foraging theory?

Answer 1

• Whether an item is included in an animals diet should not depend on how common that item is
• Poorer items should be included in the diet only if better items are rare

Question 2

Give an example of when the foraging theory formula worked

Answer 2

(Krebs et al. 1977)
Conveyor belt with different sized prey on it:
- When big prey were common, birds took only the big prey.
- When big prey were rare, birds took both big and small prey.
- Predictions were quantitatively correct.

Question 3

Give an example of when the foraging theory formula did not work

Answer 3

(Caraco et al. 1980)
Birds were able to take from 2 different feeders, however when they took from one the other dropped seeds too i.e they can only take from one each time they go. Both feeders gave the same overall amount of seed but one gave it in consistent amounts and one varied
- When the average number of seeds was high, birds always chose the more consistent feeder.
- When the average number of seeds was low, birds always chose the more variable feeder

Question 4

Why does variability matter in the foraging theory?

Answer 4

Because the animal needs a certain amount of food to survive so will behave differently depending on the variability. Will choose riskier options if they do not have enough food

Question 5

What are 3 factors which affect the foraging theory?

Answer 5

Variability in prey
Danger involved on hunting/ finding prey
What they have learnt about prey

Question 6

What did Werner et al 1983 study on bluegill and bass show?

Answer 6

That the presence of danger (predators) causes changes in prey sought after. Had pond split into two, one side just bluegill and one side blue gill and bass

• Adult bluegill foraged in open water, and they grew at the same rate, on both sides.
• Juveniles used open water on the bass-free side, and foraged in the vegetation on the side with bass.
• Juveniles grew 27% slower on the side with bass.

Question 7

What did Muzherjee and Heithaus 2013 study on Araneus trifolium (shamrock orbweaver) show?

Answer 7

That predators avoid dangerous prey

• The predator (araneus trifolium) used less successful hunting techniques on more dangerous prey because there was less chance it would get injured using that technique

Question 8

How does learning affect the foraging theory?

Answer 8

The way in which an animal forages depends on what they have learnt/ practised - more likely to use the technique they have got good at