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Lecture 6 Communication & Sexual Selection Sept. 27, 2010 1 Today’s topics • • • • 1. What is communication? 2. Modes of communication. 3. Function of communication. 4. What is sexual selection? – Intersexual selection – Intrasexual selection Sept. 27, 2010 2 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. Sept. 27, 2010 3 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 Sept. 27, 2010 4 Properties of signals • Discrete vs. Graded – Discrete (digital) simple • On or off – Graded (analog) variable • range of intensity • Vocalization signals are often graded. Sept. 27, 2010 5 Properties of signals cont… • Composite signal – combination of 2 or more signals. Sept. 27, 2010 6 Mammals can usually detect dishonest signaling or “deceit” • Elephant seals males may pretend to be females to sneak in for a copulation. Sept. 27, 2010 7 Modes of communication • • • • • Odor – usually pheromones Sound Visual Touch Electric field? Sept. 27, 2010 8 Odors • Priming pheromones – produce a generalized response – Example = induces estrus • Signaling pheromones – rapid motor response – Example = induces fear Sept. 27, 2010 9 Odor – urine or feces Sept. 27, 2010 10 Odor – glands Sept. 27, 2010 11 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 Sept. 27, 2010 12 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 Sept. 27, 2010 13 Sound Ultrasonic sound – frequencies above those audible to humans (>20,000 Hz). Sept. 27, 2010 14 Sound • Infrasonic sound – frequencies below those audible to humans (<20Hz) Sept. 27, 2010 15 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 Sept. 27, 2010 16 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. Sept. 27, 2010 17 Vision • Flagging behavior – Distracting predators from others – Warning other members – Confusing predators – Signaling the predator – Eliciting premature pursuit Sept. 27, 2010 18 Vision • Signals – Antlers – Pelage – Bristling of pelage – Tail-wagging – Snarling – Stamping – Raking Sept. 27, 2010 19 Touch • Grooming • Initiating mating • Simulation excretion Sept. 27, 2010 20 Electric field • Little evidence that mammals use electric fields for communication – Common in some fish and frogs Sept. 27, 2010 21 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 Sept. 27, 2010 22 Alarm • Signal to alert group members of danger. – • http://www.youtube.com/watch?v=evSHfFgbvcA http://www.youtube.com/watch?v=WilEzT73aHY Sept. 27, 2010 23 Wolf communication http://www.youtube.com/watch?v=_UH-6r5jrGI Chimpanzee communication http://www.youtube.com/watch?v=A1WBs74W4ik&feature=channel Sept. 27, 2010 24 “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? Sept. 27, 2010 25 Sexual Selection • A process that produces anatomical and behavioral traits that affect an individual’s ability to acquire mates. Sept. 27, 2010 26 Intersexual Selection • Members of one sex choose certain mates of the other sex Sept. 27, 2010 27 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. Sept. 27, 2010 28 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? Sept. 27, 2010 29 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 Sept. 27, 2010 30 Intrasexual selection • One sex compete among themselves for access to the other sex. – Highly ritualized battles. Sept. 27, 2010 31 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. Sept. 27, 2010 32 Sperm competition • Mate guarding • Sperm dilution • Copulatory plugs (rodents, bats, and some primates) – glandular secretion Sept. 27, 2010 33 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. Sept. 27, 2010 34