Animal Behaviour: Psych'Biol' 3750

1
Animal BehaviourPsych./Biol. 3750

• Lecture 10 September 30, 2009

2
Feeding Decisions (Chapter 10)

• 1. What to eat
• 2. Where to eat (when to leave)
• 3. Behavioral trade-offs
• Group foraging
• Predation (ch 11)

3
1. What to eat

• Search image focus on abundant prey
• Specialists versus generalists
• Barn owls meadow voles

4
Barn Owls are Meadow vole specialists
5
Net rate of energy intake

• Food eaten minus energy used getting the food
• Search time
• Pursuit time
• Handling time

6
Gray Jays of Salmonier Line
7
Change in handling times changes food preferences
8
Effects of increased handling or search time

• Increase search or handling time for fat
  decrease preference

9
What to eat?

• Great tit - mealworms (figs 10.4 10.5a)
• Density of large prey most important in model
  (see box 10.1)
• BUT some small prey are eaten

10
Diet breadth in bluegill sunfish

• Manipulate density and sizes of Daphnia (Fig
  10.5b)
• Theory - Zero-one rule Only take largest prey
  if abundant
• Actual results some small prey taken

11
Zero-one rule

• Not much support for absolute preferences
• Except for Crows whelks
• Only largest whelks taken

12
Whelk-eating Crows (Zach)
13
Where to eat

• Ideal Free Distribution
• Animals forage at most profitable sites
• Duck IFD example better choices in close or
  distant patches?

14
Ideal Free Distribution in Ducks
15
Duck Foraging Decisions
What did Harper (1982) find?
16
Foraging decisions

• Ideal Free Distribution
• Ideal despotic distribution

17
Marginal value theorem how long to stay

• Distance to next patch (Fig 10.7 10.8)
• Rate of decline in current patch average in
  habitat

18
Example Great tit foraging tree

• Time in patch (dishes) increased with distance
  between patches (Fig 10.8)

19
Optimal foraging models

• Energy Maximizers versus Time Minimizers
• Sit-and-wait foragers versus Pursuit foraging
• Constraints on optimization

20
Constraints

• Moose eat terrestrial (high energy) and aquatic
  (low energy) plants
• Salt requirement is a constraint

21
Risk Sensitive Preferences Fig 10.11 1012

• Constant (dependable) food supply risk averse
• Chance of high reward risk prone

22
Hunger and risk

• Hungry birds should be more risk prone than less
  hungry birds