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Lecture 6Communication &

Sexual Selection

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Today’s topics

• 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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• Composite signal – combination of 2 or more signals.

Properties of signals cont…

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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

• 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---Lion-Flehmen-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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SoundUltrasonic 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

• 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.

– http://www.youtube.com/watch?v=evSHfFgbvcA

• http://www.youtube.com/watch?v=WilEzT73aHY

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http://www.youtube.com/watch?v=_UH-6r5jrGI

Chimpanzee communicationhttp://www.youtube.com/watch?v=A1WBs74W4ik&feature=channel

Wolf communication

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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.