4: Optimal foraging Flashcards
why can we make precise predictions on behaviour?
behavioural ecology has strong theory
what is the optimality logic?
selection will favour animals that forage most effectively
what is optimality modeling used for? (3)
- used to determine the best course of action for an animal
- insights into optimal foraging (often graphically)
- predict how and animal should optimise its own food intake or food provisioning to young per unit time
what ideas did John Maynard Smith introduce?
ideas from economic theory and applied these models to animal behaviour
- developed optimality modelling
in a Zach study 1979 what was the study and what were the observations ? (3)
whelk choice by North western crows in USA
- always select large whelks (3.5-4.4cm)
- drop them from 5m onto rocks to break them open and eat body inside the shell
- keep dropping the same whelk until it breaks
in a Zach study 1979 what were the predictions? (3)
- large whelks should break easier at 5m than small whelks
- whelks dropped at <5m should be less likely to break but if >5m no more likely to break
- chances of whelk breaking should be independent of number of times its dropped - each time its dropped it has the same chance of breaking
in a Zach study 1979 after dropping whelks from a tower on the beach from different heights what were the results found? (6)
- large whelks take fewer drops to crack (5 compared to 18 for small)
- larger whelks have more calories
- 5m is the optimal height with 5.6 being the min energy expenditure
- if drop from too high then whelk may be stolen before reaching it
- chance of whelk breaking not affected by number of previous drops
- optimal behaviour by dropping from 5m and using the same whelk until it breaks
what can a hypothesis based on cost benefit logic that is incorrect lead to?
further insights
why may a hypothesis based on cost benefit logic be incorrect? (4)
- animal may not have been well designed by selection (not yet evolved to changing environment)
- observations may have been inappropriate so need to re-assess experimental design
- important factor may have been omitted from the model
- assumptions may not have been valid for the species studying
describe the predictions of the oystercatcher study on constraints on foraging
predicted to select large mussels that yield the most food
what were the results of the oystercatcher study on constraints on foraging
- birds selected mussels smaller than predicted as cant open the largest ones
- if only mussels that can be opened are considered then the optimum size is 50mm which matches observations
what do moose need to eat and why must they carefully select what they eat?
energy rich low sodium deciduous forest leaves or sodium rich low energy aquatic vegetation surrounding lakes
- plants may be deficient in nutrients
in the moose what can set a limit on the total food it can process daily?
stomach space- rumen constraint
In Belovsky 1978 optimal foraging approach on moose what was found? (5)
- energy gained from either lots of aquatic vegetation or a little terrestrial
- cant just exist on aquatic plants
- only a small area satisfies all constraints
- constraints include energy, sodium and rumen
- diet lies trying to maximise energy intake
what is the general economic model also known as?
- what does it predict?
Charnovs marginal value theorem
- how animals should forage in a patchy environment
