Transcript Lecture 6

Lecture 6
Communication &
Sexual Selection
Sept. 27, 2010
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Today’s topics
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1. What is communication?
2. Modes of communication.
3. Function of communication.
4. What is sexual selection?
– Intersexual selection
– Intrasexual selection
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Communication (biological)
• An action on the part of one organism (sender)
that alters the probability of occurrence of
behavior patterns in another organism (the
receiver) in a fashion adaptive to either one or
both of the participants.
• Ultimately, communication functions to increase
fitness.
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Displays and Signal
• Display – behavior pattern that conveys a
message from one individual to another.
• Signal - the physical form in which a
message is coded for transmission through
the environment
– Sound, color, odor, or postures
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Properties of signals
• Discrete vs. Graded
– Discrete (digital) simple
• On or off
– Graded (analog) variable
• range of intensity
• Vocalization signals are often graded.
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Properties of signals cont…
• Composite signal – combination of 2 or
more signals.
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Mammals can usually detect
dishonest signaling or “deceit”
• Elephant seals males may pretend to be
females to sneak in for a copulation.
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Modes of communication
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Odor – usually pheromones
Sound
Visual
Touch
Electric field?
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Odors
• Priming pheromones – produce a
generalized response
– Example = induces estrus
• Signaling pheromones – rapid motor
response
– Example = induces fear
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Odor – urine or feces
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Odor – glands
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Odor – reception
• Flehmen – retraction of upper lip to collect
scents (especially common during breeding season)
•
http://thewildsource.com/tws/blog/post/2010/08/Mapula-Lodge-Video---LionFlehmen-Response.aspx
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Sound
• Immediate communication of current conditions.
• Vast inter and intraspecific differences in
frequencies and amplification of sound
– High frequencies = short-distance communication
– Low frequencies = long-distance communication
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Sound
Ultrasonic sound – frequencies above those
audible to humans (>20,000 Hz).
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Sound
• Infrasonic sound – frequencies below
those audible to humans (<20Hz)
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Sound
• Does sound communication always
employ the vocal cords?
– Moose = antler raking
– Beaver = tail slap
– Whale & dolphin = breaching & tail-slapping
– Banner-tailed kangaroo rats = foot drumming
• Also rabbits, ungulates, spotted skunks, elephant
shrews, and some marsupials
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Vision
• Precise communication with regards to
space and time.
• Usually only effective during daylight and
over short distances
• Social and diurnal mammals rely heavily
on visual cues.
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Vision
• Flagging behavior
– Distracting predators from
others
– Warning other members
– Confusing predators
– Signaling the predator
– Eliciting premature pursuit
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Vision
• Signals
– Antlers
– Pelage
– Bristling of pelage
– Tail-wagging
– Snarling
– Stamping
– Raking
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Touch
• Grooming
• Initiating mating
• Simulation excretion
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Electric field
• Little evidence that mammals use electric
fields for communication
– Common in some fish and frogs
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Additional Functions of
Communication
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Group spacing and coordination
Recognition (next lecture)
Reproduction (next lecture)
Aggression and Social Status (next lecture)
Alarm
Hunting for food
Giving and soliciting care (next lecture)
Soliciting play
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Alarm
• Signal to alert group members of danger.
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•
http://www.youtube.com/watch?v=evSHfFgbvcA
http://www.youtube.com/watch?v=WilEzT73aHY
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Wolf communication
http://www.youtube.com/watch?v=_UH-6r5jrGI
Chimpanzee communication
http://www.youtube.com/watch?v=A1WBs74W4ik&feature=channel
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“playing”
•
http://www.youtube.com/watch?v=fLhddID1-To
• Occurs widely in mammals, but is very
rare in other taxa.
– Explanation is debatable
• Practice motor skills?
• Enhance muscle development?
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Sexual Selection
• A process that produces anatomical and
behavioral traits that affect an individual’s
ability to acquire mates.
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Intersexual Selection
• Members of one sex choose certain mates
of the other sex
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Indicator models (good genes) –
assume that the trait favored by females in someway
indicates male fitness.
• Handicap hypothesis – males possess
costly traits to show that they must be fit to
be able to afford them.
– Important to this hypothesis is the notion of
“truth in advertising”.
• Handicap must be honest and linked to overall
genetic fitness.
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Symmetry
• Symmetry of paired traits may indicate
fitness.
– Greater asymmetry is associated with low
food quality and quantity, habitat disturbance,
pollution, disease, and genetic factors such as
inbreeding, hybridization, and mutation.
– Injury?
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MHC & body odor
• Major histocompatibility complex
– Large genomic region in most vertebrates
– Plays an important role in immune system
and autoimmunity
– May allow mammals to recognize genetic
similarities in others.
– Mus musculus
• Body odor and symmetry
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Intrasexual selection
• One sex compete among themselves for
access to the other sex.
– Highly ritualized battles.
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After copulation, the fight
continues..
• Sperm competition – a situation in which
one male’s sperm fertilizes a
disproportionate number of eggs when a
female copulates with more than one
male.
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Sperm competition
• Mate guarding
• Sperm dilution
• Copulatory plugs (rodents, bats, and some
primates) – glandular secretion
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Sexually dimorphic
• Difference between the sexes in form,
usually size.
– Males often larger than females.
– Opposite in microtines (subfamily Microtinae),
most females larger than males.
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