How free are real animals to move groups

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How free are real animals to move groups?

• Ecology of Groups
• 24-October 2007

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Different groups

• Social Mammalian Group
• Flock of Birds
• Eusocial insects
• Migrating pride

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Mammalian group

• Lion pride
• Group structure
• Related females i.e. Sisters, Cousins, Aunts etc.
  
• Males ,who are unrelated to the females, but are
  usually related to each other.
• Access to the group

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Lion Pride

• Females trying to access the group.
• Costs and benefits.
• Males trying to access the group.
• Costs and benefits.

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Shoals
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GenderDiffering evolutionary pressures

• Female
• Decision to move groups is more group size
  related
• Natural selection pressure

• Male
• Decision to move groups is more gender
  related
• Sexual selection pressure

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Context

• Feeding
• Foraging benefits
• versus
• Food competition
• When priority is feeding fish
• choose to form small groups

• Anti predation
• Large group reduced per capita risk of
  predation
• 1.Earlier predator detection
• 2. Numerical dilution of risk
• 3. Predator confusion during attacks
• When priority is anti predation
• fish choose to form large
• groups

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Colonial Nesting Birds
Kittiwakes

• Age Juveniles vs. Adult
• Natal dispersal vs. Breeding dispersal
• Sex Males vs. Females

www.iol.ie
www.forthseabirdgroup.org.uk
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..

• Leaving Death
• Divorce of mate, Relatedness
• Going between Death of juveniles
• Joining Inferior nesting sites / older birds
  /out-breeding- dissimilar genotypes

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Migrating Animals

• Reasons why animals migrate
• More liveable conditions
• Find Food in a new area-Wildebeest
• Breed -Salmon
• A place to hibernate-Brown bats

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Benefits for migrating species

• Safe in large numbers against predators
• - More eyes to see.
• - Younger/Older animals.
• - Confusing the predator.
• Awareness of food source
• Increased chance of passing on genes
• Wildebeest females copulate with several males.
• Decreased energy cost
• - Geese fly in V shape.
• Longer days feed
• Larger clutches of eggs

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Costs of migrating groups of animal

• Large energy expenditure in migrating.
• Food source of interest not adequate to support
  all individuals.
• Misinterpretation in Communication among
  migrating herds.

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Eusocial Animals

• 3 Defining Features
• Reproductive division of labour
• Overlap of generations
• Co-operative care of young
• Ants, aphids,
• wasps, bees, shrimp

www.lawestvector.org
science.kennesaw.edu
www.cirrusimage.com
bio1152.nicerweb.com
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Leaf-cutter ants Atta and Acromyrmex species
www.edible.com

• Due to specialised structure of these
  super-organisms
• Each individual functions almost as an organ
• Role decided from birth

www.mudslide.150m.com
www.iusi.org
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• Leaving the group
• Is unimaginable
• Actual moving from
• Would not survive alone
• Joining a new
• Would never be accepted

jnocook.net/dust/bin/noway.jpg
www.antfarmz.net
www.uq.edu.au
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All in All

• The simple answer is an animals freedom to move
  depends on
• The species
• And on chance

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References

• Context-dependent group size choice in fish.
  Animal Behaviour 2004,67, 155-164.
• The effect of sex and shoal size on shoaling
  behaviour in Danio rerio. Journal of Fish Biology
  (2005) 67, 13181326.
• http//www.divethedream.com/PhotoGallery/ScubaPics
  /SodwanaBay/SpadefishShoal1.jpg
• http//bio.research.ucsc.edu/barrylab/classes/ani
  mal_behavior/IMAGES16.DIR/PREDINS.JPG
• Interactions between shoal size and conformity in
  guppy
• social foraging. Animal Behaviour, 2001, 62,
  917925