Optimal foraging

Question 1

What is optimality modelling used to determine?

Answer 1

Used to determine the best course of action for an animal e.g maximising food intake/offspring provisioning rate per unit time

Question 2

Describe what insights can be gained from an incorrect prediction on optimal behaviour

Answer 2

• The animal may not have been well ‘designed’ by selection
• Observations may have been inappropriate
• An important factor may have been omitted from the model
• Assumptions of the model may not have been valid for the species under observation

Question 3

Describe how nutrients can be a contraint to optimal foraging

Answer 3

• Nutrient quality is of more important to herbivores
• Stomach space is also an additional constraint (as herbs have to eat more)

Question 4

Describe Charnov’s Marginal Value Theorem

Answer 4

• Suggests that an animal should leave a resource patch when the rate of gain within the patch equals the average rate of gain for the entire environment
  e.g It’s like saying, “I’ll move on when the berries here aren’t any better than the berries elsewhere.”
• This decision is based on diminishing returns of staying in the patch and the opportunity cost of forgoing resources in other patches.

Question 5

What are some assumptions of Charnov’s Marginal Value Theorem?

Answer 5

• That the animal knows travel time between patches (Is true for returning to a nest, but not for flower patches etc.)
• Travel costs = patch costs
• Patch profitability is known
• No predation

Question 6

Describe study into Whelk choice by Northwestern crows

Answer 6

Crows behave optimally:
- They choose large whelks
- Drop them at 5m onto rocks to break open
- Keep dropping the whelk until broken
- Preductions:
- Whelks dropped at <5 m should be less likely to break, whelks dropped at >5m should be no more likely to break = 5 m is perf
- The chances of a whelk breaking should be independent of the number of times dropped

Question 7

Give an example of how additional factors can constrain optimal foraging

Answer 7

Oystercatchers choose smaller mussels than predicted because large mussels were impossible to open

Question 8

Why do moose need to consume both aquatic plants and terrestrial leaves?

Answer 8

To meet their energy and sodium requirements