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BIOC54H3 (13)
Lecture 8

Lecture 8

7 Pages
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Department
Biological Sciences
Course Code
BIOC54H3
Professor
Maydianne Andrade

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Lecture 8
Protection should also increase with increased mobbing:
oExample: a researcher took a colony of black-headed gull, and took a bunch of
chicken eggs and layed it from the outside of the colony to deep in the colony,
where its the densest
oThe zones where they layed down the eggs : A-E : by the time you get inside of
the colony, almost a 100% of the time that the crow approaches, it will get
attacked by at least 10 individuals. Thats quite a big attack. And the percent of
succesfull predation by the crow decreases as it goes deep into the colony, and
this is the affect of mobbing and protecting offspring.
Information center effect
oIf you are in a big colony living with a group of other individuals and its very
hard to find food, you can use the information from what other individuals are
doing in the group to help you find food.
oThis is more important for species where food is mobile and hard to find
Ospreys : they skim the surface of water to find fish
The fish comes from a school of fish, which is moving. If you find a school
of fish you do really well, and if you dont find a school of fish you wont be
eating that day potentially.
They have babies in rookeries, or large dense aggregations high above the
water ( in rotten trees)
IC hypothesis predicts that individuals who are able to observe their
neighbours catching food should be more successful in eating.
Graph shows (observational study) : the # of individuals that caught a fish
that observed their neighbour returning with a fish.
Increased capacity to deal with physical challenges in the environment :
oSome species that go through a period of turper that slows down their
metabolism can do better when they are in a cluster
oPenguins cluster themselves in the Antarctic when it is very cold
oThis allows them to maintain their body heat at a higher level than they would
be able to do alone.
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Lecture 8
oBats do the same.
oNone of these benefits require cooperation
Selfish herd
oYou can have tight groups with apparently coordinated movements simply
because individuals do not want to be on the outside of the group all the time
oIf you are in a group, you are trying to move so that conspecifics are between you
and the predators.
oThats typically because the predators pick on the animals from the outside,
rather than from the inside
Although the previously mentioned benefits of group living do not require cooperation,
there are some that do: ( these require coordinated effort on the part of multiple
individuals to protect a territory boundary or to chase down predators)
oImproved territory defence :
Examples: Lions and Langurs
oImproved predation ability: sophisticated predation ability
Lions and wild dogs: pack hunting animals; coordinated , cooperative,
group hunting
When does cooperation occur?
oSo you got the groups, and you assume that group living occurs because the
benefits outdoes the costs. But when does cooperation happen?
oCooperation occurs when it increases an individuals life-time reproductive
success.
oThere is reproduction of your own offspring, as well as reproduction of your own
genes.
oWhat is being optimized is the reproduction of genetic material. Which can occur
through your own offspring as well as the offspring of your kin
oThere are 2 ways we can talk about reproductive success
Cooperation: increasing reproduction of your own offspring ( direct
fitness)
www.notesolution.com

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Description
Lecture 8 Protection should also increase with increased mobbing: o Example: a researcher took a colony of black-headed gull, and took a bunch of chicken eggs and layed it from the outside of the colony to deep in the colony, where its the densest o The zones where they layed down the eggs : A-E : by the time you get inside of the colony, almost a 100% of the time that the crow approaches, it will get attacked by at least 10 individuals. Thats quite a big attack. And the percent of succesfull predation by the crow decreases as it goes deep into the colony, and this is the affect of mobbing and protecting offspring. Information center effect o If you are in a big colony living with a group of other individuals and its very hard to find food, you can use the information from what other individuals are doing in the group to help you find food. o This is more important for species where food is mobile and hard to find Ospreys : they skim the surface of water to find fish The fish comes from a school of fish, which is moving. If you find a school of fish you do really well, and if you dont find a school of fish you wont be eating that day potentially. They have babies in rookeries, or large dense aggregations high above the water ( in rotten trees) IC hypothesis predicts that individuals who are able to observe their neighbours catching food should be more successful in eating. Graph shows (observational study) : the # of individuals that caught a fish that observed their neighbour returning with a fish. Increased capacity to deal with physical challenges in the environment : o Some species that go through a period of turper that slows down their metabolism can do better when they are in a cluster o Penguins cluster themselves in the Antarctic when it is very cold o This allows them to maintain their body heat at a higher level than they would be able to do alone. www.notesolution.com
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