Perception

1
Perception

• Animal Cognition
• Keith Clements

2
Aims

• To illustrate how perceptual systems filter
  information from the outside world.
• To describe research on prey catching in frogs
  toads, as an extreme example of the use of
  visual rules of thumb.
• To discuss the senses which are thought to allow
  homing pigeons to find their way home.

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The perceptual world

• Von Uexkull argued that the inner world
  (innenwelt) differs from the external environment
  (umwelt). The umwelt is filtered by each species
  sensory systems.

4
Sign Stimuli

• Ethologists often studied stereotyped behaviours
• Fixed Action Patterns
• triggered by Sign Stimuli
• E.g. Tinbergen (1951)
• threat mating displays elicited by red markings
  on male sticklebacks belly.
• Turkeys respond differently to bird silhouette
  depending on direction of motion

Hawk
Goose
5
Prey catching in frogs toads

• Lettvin et al. (1959) identified distinct types
  of retinal ganglion cells in Leopard frogs.
  Ganglion cells filter input by size and movement.
• Ewert, (1974, 1980) Cells in the thalamus
  tectum respond to complex stimuli, small moving
  objects trigger a sequence of responses,
  including leaning towards the object and
  attempting to catch it with the tongue.

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Visual rules of thumb
Turn towards
Avoided

• Barnard (2004) called these visual rules of
  thumb,
• These innate responses can be modified by
  learning.

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How pigeons see the world

• Narrower binocular vision than humans (35), but
  wider total field of view (340).
• Typical of preyed-upon species.
• Sensitive to ultraviolet light and have 6
  different colour receptors (humans have 3).
• They rely on vision to guide flight and identify
  edible grains, etc.

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Navigation in homing pigeons

• Pigeons do use visual landmarks.
• However when vision is obscured by frosted lenses
  they can still find their way home
  (Schmidt-Koenig Keeton, 1977)
• What other cues do they use?

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Odours as navigational aids

• Anosmic birds often show poorer homing, but the
  extent seems to vary with location.
• Strain differences?
• Housing conditions?
• Local stimuli?
• Deflecting odours with baffles (Baldacini et al.,
  1975) alters the initial heading when released.
  However baffles may influence other cues (e.g.
  sunlight)
• Birds exposed to artificial odours (Ioale et al.,
  1978) do make use of the information.

10
The sun compass

• The direction of the sun, adjusted for time of
  day, can provide a bearing. The next lecture will
  consider other species ability to track the
  passage of time.
• Schmidt-Koenig (1960) shifted pigeons internal
  clocks with artificial light. This altered
  vanishing bearings on sunny, but not overcast
  days.
• Sensitivity to polarization of light allows
  pigeons to detect the sun even if only part of
  the sky is free of cloud.
• Some migratory species (e.g. sylviid warblers
  indigo bunting) use a star compass Emlen (1970)
  used a planetarium to show that buntings would
  learn to use artificial constellations. Initially
  the axis of celestial rotation is used, but birds
  learn to recognise constellations close to the
  pole.

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Magnetic senses

• The intensity and inclination of the Earths
  magnetic field varies with position.
• Wiltschko (1968) raised robins in enclosed rooms
  with an imposed magnetic field variations in the
  inclination altered their bearing during
  migration
• Studies (e.g. Keeton, 1974) show fitting magnets
  to pigeons impairs their navigation on overcast,
  but not on sunny days.
• Here too there are conflicting findings, possibly
  related to geographical or strain differences.

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Further Reading

• Chapter 4 in Wynne covers this weeks topic.
• Theres a good summary of work on prey detection
  in toads on pages133-138 of Barnard (2004) Animal
  Behaviour Mechanism Development, Function
  Evolution. Pearson Education
• For more on navigation, and the senses which
  guide it see either
• Wiltschko, R. Wiltschko, W. (2003). Avian
  navigation from historical to modern concepts.
  Animal Behaviour, 65, 257272
• a chapter by Bingman, Jechura Kahn, in a
  cyberbook on animal spatial cognition
  http//pigeon.psy.tufts.edu/asc/Bingman/Default.ht
  m