Animal Behavior Introduction

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Animal Behavior Introduction

• Evolutionary Theory Charles Darwin
• Voyage of HMS Beagle (1830s)
• Galapagos Islands Darwins finches
• Evidence from collections and from captive
  breeding

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Darwin After HMS Beagle Voyage
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HMS Beagle
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Publication

• Alfred Russel Wallace 1858
• The Origin of Species 1859
• 2,000 copies, sold out the first day
• Controversy over natural selection

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Evolutionary Components

• Three Basic Components
• Variation (mutations) The role of chance
• Survival and reproduction
• Heritability Genes (Darwin didnt know about
  Mendels experiments)

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Variation in Genes

• Genes come in two forms, called Alleles
• Mutations are usually not successful or neutral
• Beneficial ones give the carrier an advantage

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Survival

• Malthus Populations theoretically can grow at an
  exponential rate
• Sea turtles for example, produce nests of 100
  eggs, 4 to 6 times per season
• Begin with 1 male and 1 female 500eggs
• 250 males and 250 females 125,000 offspring
• 62,500 females 31,250,000 offspring

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Competition

• Not all offspring survive
• Mortality due to competition for limited
  resources
• Mortality due to predation
• The so-called Survival of the fittest (Herbert
  Spencer)

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Reproduction

• Fitness Success at reproduction
• Individual Fitness (Darwin), and Inclusive
  Fitness (Hamilton)
• Offspring must be viable to count as a fitness
  unit (species recognition is very basic)

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Mules are a cross between a horse and a donkey
and are sterile
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Heritability

• Genes are the unit of heritability
• Bodies are vehicles for genes
• Genes code for proteins
• The genome and environment to produce the
  PHENOTYPE which drives evolution

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Vole mating systems

• Male reproduction is potentially great, female
  reproduction is limited
• Sperm vs. egg
• Internal fertilization and development
• Delivery and care of young
• So why do prairie vole males agree to be
  monogamous?

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Monogamous Prairie Voles
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Pup Retrieval (Male Parental Behavior)
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Levels of Explanation

• Ultimate Causes The evolutionary history and the
  fitness advantage of the trait
• Proximate Causes Those things that occur during
  the lifetime of the individual including genes,
  developmental processes, sensory capacities,
  learning and so on

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Prairie voles

• A gene for social bonding, V1aR
• Increased sensitivity to a hormone, vasopressin,
  in the ventral pallium, due to V1aR gene

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Prairie Vole Brain
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Experimental Test

• Inject V1aR genes into the ventral pallium
• Should increase bonding with female, even without
  mating
• Control gets V1aR in Caudate Putaman or another
  gene in the VP or CP
• Results of time spent with familiar or unfamiliar
  female

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Genes Added to Ventral Pallium and Control Groups
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Proximate cause of Monogamy in Prairie Voles

• The Proximate cause of monogamy in Prairie Voles
  is
• The V1aR gene which
• Increases the number of vasopressin receptors in
  the ventral pallium which
• Makes him bond to a single female

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Ultimate Cause of Monogamy in Prairie Voles

• Females are widely dispersed
• Unguarded females are subject to sperm
  competition, and offspring are subject to
  infanticide by other males

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Infanticide as an Adaptation

• Adaptation A specially designed process that
  solves an important problem in the environment
• Is infanticide an adaptation? Yes, it gets a
  lactating female back to sexual receptivity. No,
  its due to abnormal circumstances (crowding).
  No, its to limit the population because of
  resource scarcities.

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Infanticidal Species

• Common house mouse, Mus musculus
• Lions when a male takes over a pride
• Hanuman Langurs - new male in the group

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Infanticide by a male lion
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Females and their offspring
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Male langurs commit infanticide
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Why Infanticide?

• Group Selection? Prevent overpopulation and
  depletion of resources (Wynne Edwards)
• In general, Group Selection cannot work.
• Individuals who sacrificed themselves for the
  good of the group would not have genetic input,
  only the selfish would (George Williams)

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Individual Fitness Explanation of Infanticide

• Male lions only control a pride for about 2 years
• Mice that mate with a female show inhibited
  infanticide 18 days later
• Langurs do not show inhibited infanticide when
  population densities are low
• Its always an intruder male that commits
  infanticide