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Lecture 7

Biology 2483A Lecture Notes - Lecture 7: Optimal Foraging Theory, Mealworm, Eric Charnov

Course Code
BIOL 2483A
Hugh Henry

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Animals make behavioural choices that enhance their energy gain and reduce their risk of becoming prey.
Mating behaviours reflect the costs and benefits of parental investment and mate defense.
There are advantages and disadvantages to living in groups.
An evolutionary approach to the study of behaviour leads to testable predications.
Adult male lions often kill the cubs of another male in the pride. Why would this behavior be adaptive?
Young adult male lions are driven from the pride and may form "bachelor prides" that hunt together.
At 4 or 5 years, a male can challenge adult males in an established pride.
A female lion will become sexually receptive soon after her cubs are killed, as opposed to 2 years if she has
The new male is increasing the chances that he will sire cubs before he is replaced by another, young male.
In many species, females are more "choosy" than males in mate selection, but in some species females try to
mate with as many males as possible.
Choosy Females
Behavioural Ecology: is the study of the ecological and evolutionary basis of animal behavior.
An animals' behavioural decisions play a critical role in activities such as obtaining food, finding mates, avoiding
Proximate Causes (Immediate)- or how the behavior occurs.
Behavioural ecologists mostly focus on ultimate causes.
Ultimate Causes - why the behaviour occurs; the evolutionary and historical reasons.
Animal behaviours can be explained at different levels:
Lecture 7: Behavioural Ecology
Thursday, October 8, 2015
1:39 PM
Lecture Slides Page 1

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Certain genes or groups of genes that can explain why an animal is behaving a specific way.
Behavioural ecologists mostly focus on ultimate causes.
Many studies have documented adaptive behavioural change.
Cockroaches exposed to traps with a bait containing an insecticide plus glucose aversion, which is controlled by
a single gene.
Oldfield mice build a long entrance tunnel and an escape tunnel, possibly ad adaptation to living in open
habitats that provide little protective cover.
Deer mice construct a simpler burrow, with a short entrance tunnel and no escape tunnel.
All the F1hybrid offspring built burrows with escape tunnels, as did about 50% of backcross mice (F1
hybrid mated with deer mice).
This indicates that building escape tunnels is controlled by one genetic locus.
The two mice species can interbreed and produce fertile offspring.
Escape Tunnels
The mutation in the gene makes the glucose
taste bitter to them so they just don't want to
eat it.
Lecture Slides Page 2

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Genetic mapping also showed that entrance tunnel length was controlled by three genetic loci.
Although few studies have identified the genes, many behaviours are known to be heritable, and most are
influenced by multiple genes.
Most aspects of animal behaviour are controlled by both genes and environmental conditions.
By assuming that genes affect behaviors, and natural selection has modeled them over time, we can make
specific prediction about how animals will behave.
Individuals with an allele for a certain behavior may not always perform that behaviour, and may change
behaviour when in different environments.
Alleles and the Environment
Food availability can vary greatly over time and space.
comes down to gaining energy
An animal should basically invest in high quality food OR low quality food that doesn't require energy to
If energy is in short supply, animals should invest in obtaining the highest-quality food that is the shortest
distance away.
Forging Behaviors
Animals will maximize the amount of energy gained per unit of feeding time, and minimize the risks
P = E/t
Profitability of a food item (P) depends on how much energy (E) the animal gets from the food
relative to amount of time (t) it spends obtaining the food:
The theory assumes that natural selection acts on the forging behavior of animals and maximize their
energy gain.
An animal's success in acquiring food increases with the effort it invests; but at some point, more effort
results in no more benefit, and the net energy obtained begins to decrease
Optimal Foraging Theory:
Lecture Slides Page 3
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