Exam 3 Flashcards
How is communication used
- alarm/defense
- aggression/territorial defense
- reproduction/mate attraction
- maintenance of social relationships
What is communication
Process by which a signaler uses a specifically designed signal to modify the behavior of a receiver
What info is conveyed by signals
- Location and identity of signaler
- Information about signaler (quality, intentions)
- Info about environment
- Prescription for reaction by receiver (some signals may serve more than one function)
May be conflict of interest in communication (what are trade offs?)
Sometimes advantageous to respond, sometimes not.
Trade offs:
- signaling requires time and energy
- risk of eavesdropping by illegitimate receivers
- risk of deception and exploitation (ex - predators making prey signals to attract them)
Fitness payoff matrix
Signaler Receiver
+ + True comm.
- - Eavesdropping
+ - Deception
Modalities
- diff means of communication
Types: Chemical (pheromones, scent marking) Visual Acoustic Tactile
Communication is adapted to ______
- stimulus filtering ability of receiver; ecological conditions
Composite signals
Signal containing more than 1 element. Signals may also be graded or discrete.
Ex: Zebras.
Ear position: discrete (ears either up or down)
Mouth position: graded (intensity signal - mouth can be open in diff amounts)
Altogether: composite signal, shows emotional state and displays how strong it is with a discrete and graded signal together to different degrees.
– ear position + mouth position = composite signal
Sensory exploitation
Adaption of signal to receiver’s stimulus filtering
- how natural selection shapes communication signals. Shaped to work best in animal’s environment.
Signals are more effective if
- Highly detectable to receiver (sensory exploitation - matches currently existing sensory systems)
- Receiver pays attention (matches current sensory processing systems)
- -ex: water mites. Male waves leg in front of female to signal her to lay eggs for fertilization. Movement of leg mimics movement of prey through water, which gets their attention. (Also, cichlid egg spots, orange guppies)
Signals may therefore be shaped by pre-existing preferences in receivers
- how do you test?
- introduce novel signal see how receivers respond.
- –ex: artificial white head crests on zebra finches. Use white because females attracted to white feathers - line nests with it.
- –ex: swordtail. What came first, preference or signal? Female swordtail attracted to males with large swords. Did females have preference for sword or did it evolve for another reason and become associated with mate attraction later?
- —preference came first. If you attach fake swords to platt fish, females prefer those male. Suggests preference evolved in common ancestor between plates and swordtails.
Signals may have been present in ancestors but lost
In these cases, animals may still respond to signal in vestigial manner
Ex: S. Vinegatus males respon submissively to males painted with blue patches (common ancestor had patches but they don’t)
- males lost blue belly for unknown reason but still respond to it
Adaption of signals to animal’s ecology (ex: ant foraging communication)
Different modalities appropriate under different conditions
- Leptothorax: scavengers
- food immobile, no great hurry. Must recruit other ants to carry food to colony through chemical stimulation (regurgitation). Lead other ants tactilely (constant touch between antennae and abdomen) - Fire ants: feed on large, mobile prey. More urgency for communicating.
- secrete odor trails that disappear quilt (so ants can follow new trails as animal is moving)
- fast recruitment necessary, prey changes position - Leaf cutter ants: use plants to grow fungi. (No rush)
- leave long-lasting odor trail- create physical paths through habitat
Adaption within a modality: acoustic communication example with birds
Songs of forest birds: pure, low-frequency whistles
Songs of grassland birds: “buzzy” trills
Whistles carry farther in forests without echo degradation. Trills less degraded by wind, don’t need to worry about it bouncing off of objects and bouncing back to interfere with new trills produced
Ex: also found in gray-cheeked Mangabays. “Whoop-gobble” for inter group calling. (Low pithed, pure tone. Used sparingly to communicate with other social groups over territorial disputes.)
“Scream” for intragroup communication. High pitched, multiple tones. Doesn’t transmit as far, less eavesdropping risk by predators.
Origins of signals
May be derived from movements related to other biological functions or conflict behaviors (expressions of motivational conflict)
- later evolved to be part of normal communication signals
Conflict behaviors
Behaviors that are normal now, evolved in different context previously.
Redirected behavior
Context-appropriate behavior directed towards inappropriate target
Ex: when gulls face off in territorial dispute. Pull clumps of grass out of ground as signal to other gull. Biting other gull is dangerous, so bite grass instead. Now is part of communication system.
Displacement behavior
Out of context behavior that diffuses tension
Ex: when wildebeest engage in aggressive behavior. Will stop and start grazing. Many animals when sorting out dominant status will start grooming or do other things that seem inappropriate. These have roots in displacement behaviors - things that help ease anxiety in the individual.
How do these behaviors become signals?
Gain signal status through ritualize room
- the evolutionary process by which behaviors previously unrelated to communication gain “signal value” (acquire specific meaning to others)
- ex: submissive behavior in dogs - no longer reflexive respond to impending attack; may display behavior before signs of aggression occur to act as submissive communication
How ritualization changes a behavior to give it signal value
- Exaggeration
- Repetition
- Increase in conspicuousness
- -ex: anole push-up display is asynchronous with background motion. Timing of push ups such that here is no way that it can be confused for anything else moving around it. Example of display that has become more conspicuous because if how it’s done, not necessarily because it is exaggerated - Stereotyping: signal is produced in approximately the same species-typical way each time
- Morphological support (development of feature that enhances communication. Ex- anole dewlap. Adds to detectablility of signal, likelihood that other lizards pay attention)
- Possible addition of other signals
Ritualization of peacock ritual ship (inferred by Cladistic analysis)
Feeding attracts other birds. Many pheasants peck at ground while they feed - may peck at ground to attract birds while not feeding. Closer ancestors to peacock spread wings and peck at ground while feeding. Others bend towards ground like they’re going to peck but don’t. These movements part of courtship behaviors (attract other birds by pretending to feed)
–origin behavior was feeding behavior that was attractive; ritualization process moved behavior away from biological feeding behavior into something that was pure communication detached from feeding
Factors that select for honesty (true quality or intention of signaler)
- Anatomical or physiological limitations (ex- size of male toad correlates negatively with call pitch. Females prefer low-pitched. Ex- antlered flies’ antler size for sparring correlated to body size)
- Costly displays: only best quality individual can afford costly display (condition-dependent signaling) (ex- stotting by gazelles. Jump straight into air. Honest indicator to predators about how fast they can run. Ex- treadmill workout of male side-blotched lizards. Can do fewer push ups/cannot hold up threat display postures as long after workout.)
- Signaler are constantly probed for honesty (ex- Harris sparrow. Amount of black on head tied to dominance position in flock. Signal works because they are constantly testing each other to see if others able to back up color. Researchers put black on some birds heads, injected others with testosterone without making them darker, then made some darker and did testosterone injections. Only those with both black head and testosterone rose in and maintained status)
Why do animals usually settle disputes through displays?
Better to assess chances before engaging in costly and dangerous fights. Escalation occurs only if asymmetry unclear (if they seem equally matched)
When does deception work?
Selection for “sales resistance” has not caught up with “deceptive sales pitch” yet - has not evolved.
– circumstantial evidence: Australian beetle mating with beer bottles that have similar look to beetles’ wing coverings
- cost of ignoring signals is high
- -deceptive alarm calls in birds, primates, anglerfish
Firefly deception
Photuris female lures Photinus males with deceptive flash pattern. Eats them, uses defensive chemicals from Photinus to protect itself from jumping spiders.
How do animals respond to predation
- by making detection less likely (crypsis)
- making attack less likely (aposematic coloration, display of defensive ability, predatory mimicry, association with protective species)
- make capture less likely (deimatic coloration, disruptive coloration, physical deterrents, vigilance, misdirection, run, live in group)
- making consumption less likely
Making detection less likely
Crypsis
- behavioral (hiding, freezing, moving like background)
- counter-shading
- disruptive citation (ex-striping)
Dies crypsis work? Evidence.
Jays rewarded or correctly pecking at screens with moths present. More successful if moths conspicuous.
Prey must sometimes trade crypsis for competing selective pressures
Guppies: predation risk vs. sexiness (adaptive trade-off: population level)
Birds in winter: predation risk vs. starving risk
- spend more time feeding in “dangerous places” on cold days. Tactical trade off at individual level.
