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Lecture 7

Biology 2483A Lecture Notes - Lecture 7: Optimal Foraging Theory, Behavioral Ecology, Backcrossing


Department
Biology
Course Code
BIOL 2483A
Professor
Hugh Henry
Lecture
7

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Animals make behavioral choices that enhance their energy gain and reduce their risk of becoming prey
Mating behaviors 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 predictions.
Adult male lions often kill the cubs of another male in the pride. Why would this behaviour be
adaptive?
o Youg adult ale lios are drie fro the pride ad ay for ahelor prides that hut
together.
o At 4 or 5 years, a male can challenge adult males in an established pride.
o If successful, the new male may kill cubs recently sired by the vanquished male.
o A female lion will become sexually receptive soon after her cubs are killed, as opposed to 2
years if she has cubs.
o The new male is increasing the chances that he will sire cubs before he is replaced by
another, younger male.
I ay speies, feales are ore hoosy tha ales i ate seletio, ut i soe speies
females try to mate with as many males as possible.
Behavioural ecology
Is the study of the ecological and evolutionary basis of animal behaviour.
An animals behavioural decisions play a critical role in activities such as obtaining food, finding
mates, avoiding predators.
Animal behaviours can be explained at different levels:
o Proximate causes (immediate)or how the behaviour occurs.
o Ultimate causeswhy the behaviour occurs; the evolutionary and historical reasons.
behavioural ecologists mostly focus on ultimate causes.
Many studies have documented adaptive behavioural change.
o Cockroaches exposed to traps with a bait containing an insecticide plus glucose evolved
glucose aversion, which is controlled by a single gene.
After ahile, they did’t like gluose ayore
Single genetic locus controlling behaviour
o Oldfield mice build a long entrance tunnel and an escape tunnel, possibly an adaptation to
living in open habitats that provide little protective cover.
o Deer mice construct a simpler burrow, with a short entrance tunnel and no escape tunnel.
Genetic locus that determine whether or not a deer mice will build a tunnel
The two mice species can interbreed and produce fertile offspring.
All of the F1 hybrid offspring built burrows with escape tunnels, as did about 50% of
backcross mice (F1 hybrids mated with deer mice).
This indicates that building escape tunnels is controlled by one genetic locus
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.
Individuals with an allele for a certain behaviour may not always perform that behaviour, and may
change behaviour when in different environments.
But by assuming that genes affect behaviours, and natural selection has molded them over time,
we can make specific predictions about how animals will behave.
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Foraging Behaviour
Food availability can vary greatly over time and space.
If energy is in short supply, animals should invest in obtaining the highest-quality food that is the
shortest distance away.
Optimal foraging theory: Animals will maximize the amount of energy gained per unit of feeding
time, and minimize the risks involved.
The theory assumes that natural selection acts on the foraging behaviour of animals to maximize
their energy gain.
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:
An animals 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.
In a study of Parus major, proportions of prey types and encounter rates were varied.
The time it took birds to subdue and consume the prey (handling time) was measured.
The model correctly predicted consumption rates of large mealworms as profitability of prey items
varied
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