BIOL1003 Lecture 25: Behavioural Ecology- Lecture 2- Making Decisions
Making Decisions
Making decisions
Decisions can affect an animal’s chances of survival and reproduction
We assess whether animals make adaptive decisions
Three methods to study adaptive questions about behaviour:
oObservation
oExperiment
oOptimality modelling
Not that animals can make conscious decisions, but natural selection has resulted in
behaviours that help an animal survive and reproduce
Provisioning of young by Siberian Jays
Have well-hidden nests, but parents visiting a nest with food for young can give away
its location to predators
Parents therefore should visit less when there are more predators around
Eggers found that jays fed at the greatest rate very early in the morning before most
predators became active
This feeding pattern was absent in areas without predators, and could be prompted
by playbacks of predators’ calls, suggesting that jays indeed time feeds to avoid
being spotted by predators
Jays face the dilemma that reducing the risk of predation increases the risk of
starvation, hence an intermediate rate of feeding would be the best
Optimal decisions
Eggers did not make quantitative predictions about the best rate of feeding, because
he did not have precise measures of how parental visit rate affected the nestlings’
predation risk, growth and subsequent survival
Other studies, particularly of foraging behaviour have made quantitative predictions
about animal behaviour
The “optimality” approach to studying adaptation is based on making predictions
about the optimal (best) behaviour, and testing these predictions with observations
and experiments
If the animal behaves as predicted, we have some confidence that we understand
the function of the behaviour
E.g. studies of crabs preying on mussels show that crabs select the size of mussel
that roughly maximises their rate of energy gain
Reproductive decisions
Although many studies of optimal decisions have examined foraging behaviour, the
optimality approach can be applied to other behaviour, including reproductive
behaviour
E.g. the duration of copulation in dungflies appears to maximise the overall rate at
which males fertilise eggs
Conditional decisions
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Document Summary
Decisions can affect an animal"s chances of survival and reproduction. We assess whether animals make adaptive decisions. Three methods to study adaptive questions about behaviour: observation, experiment, optimality modelling. Not that animals can make conscious decisions, but natural selection has resulted in behaviours that help an animal survive and reproduce. Have well-hidden nests, but parents visiting a nest with food for young can give away its location to predators. Parents therefore should visit less when there are more predators around. Eggers found that jays fed at the greatest rate very early in the morning before most predators became active. This feeding pattern was absent in areas without predators, and could be prompted by playbacks of predators" calls, suggesting that jays indeed time feeds to avoid being spotted by predators. Jays face the dilemma that reducing the risk of predation increases the risk of starvation, hence an intermediate rate of feeding would be the best.
