Territoriality

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Territoriality

• Lecture 7

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Territoriality

• One of the major roles of communication systems
  in animals is to advertise and defend
  territories.
• A territory is an area defended by an individual
  (or group) for its (their) exclusive use
• Defence and exclusiveness of use are the key
  features

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Territoriality

• A territory is more than just the area
  individual frequents
• Home range the area over which an animal ranges

Territory
Home range
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Territorial defence

• Can involve large energy expenditure
• Risk of injury or even death
• An animals face a trade-off because resources
  invested in territory defence cannot be available
  for other activities
• On the other hand maintaining a territory may be
  essential for animals to acquire enough food,
  mates etc.

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Territorial defence

• Common in many mammals, birds, amphibians,
  insects
• Spring peepers, for example spend long periods
  each night advertising and defending small
  territories

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Types of territories

• Breeding or nesting sites
• Feeding areas
• Both breeding and nesting
• Leks small territories used only as display
  grounds

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Territoriality

• Because time invested in territorial defence is
  not available for other important activities
• For natural selection to select for territorial
  behaviour resources must be
• limiting
• defendable

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Territoriality

• Should persist if the cost of investing time and
  energy in defence is outweighed by the benefits
  of exclusive access to the limited resource

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Territoriality

• If resources are limiting e.g., nesting sites for
  cavity nesting species territoriality should
  evolve
• Feeding territories of insect eating bats are
  less likely to evolve
• Prey are ephemeral

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Territory advertisement

• Scent marking Mammals
• Vocalizations Birds, amphibians, mammals,
  insects
• Visual displays Birds, mammals

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Territory advertisement

• Reduces energy required to maintain territories
• Initial energy expenditure can be high
• Individual recognition signals can reduce the
  cost of defence

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Badges of Status

• Examples
• Red-winged blackbird
• Yellow warbler
• House sparrow
• Ungulates
• Convey animals status, reduce energy expenditures
  due to fighting

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Red-winged blackbird

• Badges are sometimes coverable
• Not always looking for a challenge
• Can adjust their signals to show their intent

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Red-winged blackbird

• Badges are honest signals of status
• Birds with artificially enhanced patches
• Loose their territories
• Challenged by birds that would otherwise not
  bother

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Red-winged blackbird

• Birds with artificially reduced patches
• Loose their territories
• Challenged by birds that would otherwise not
  bother

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Red-winged blackbird

• Remove the ability to cover patches
• Loose their territories
• Birds spend all of their time fighting because
  they are always appear in an aggressive posture

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Males with difficulty holding territories

• May adopt alternate strategies
• Satellites or sneakers
• Avoid the costs of territorial defence
• Hang around other males territories
• Sneak copulations when the territory holders are
  away feeding

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Examples

• American (common) Toads
• Tree swallows
• Bluegill Sunfish

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Sneaker strategy

• May be a developmental stage
• Permanent Strategy

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Bluegills

• Two types of male
• Territorial males
• Sneakers
• Genetically distinct
• Sneakers mimic females

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Mixed ESSs

• Natural selection should favour the most
  successful strategy
• Best strategy may depend on what other are doing
• e.g., rock paper scissors game