Some functions of communication
Group spacing and coordinationSpecies recognition
Kin recognitionReproduction
Agonism and social statusAlarm
Giving and soliciting of foodSoliciting play
Synchronization of hatching
What is communication?
“Action on the part of one organism (or cell) that alters the pattern ofbehavior in another organism (or cell) in a fashion that is adaptive
to either one or both participants” (E.O. Wilson, 1975)Problem with this definition
If a mouse rustled in the grass, and thereby enabledan owl to catch it, this would be considered communication
“The transmission of a signal for one animal to another such that thesender benefits, on average, from the response of the recipient”
(Slater, 1983)
What does this latter definition assume?
What types of communication signals do animals use?
Some signals are discrete (e.g., ear position),
whereas others are graded (e.g., degree to which mouth
is opened)
Further, note that the meaning of a signal (e.g., opening of
mouth) can vary depending on the context in which it is
displayed
Any given communication signalcan serve multiple functions
e.g., a lion’s roar can function as a spacing device forneighboring prides, as an aggressive display in fightsbetween males, or as a means of maintaining contact
among pride members
Some communication signals even appear to change the meaningof those that follow (i.e., function as metacommunication)
Dogexhibitingplay-bow
Darwin developed the principle of antithesis to help explain the diversityof communication signals within a species
threatening posture
submissive posture
Note that the postural features of these two signals are diametrically opposed to one another (e.g., ear and tail positions, shape of the spine, and piloerection)
This has the effect of accentuating the differences between each signal
Feature of channel
chemical
auditory
visual
tactile Range
long
long
medium
short
Transmission rate
slow
fast
fast
fast
Night-use?
yes
yes
no
yes
Ability to go past objects
good
good
poor
poor
Fade-out time
slow
fast
fast
fast
Locatability
variable
medium
high
high
Energetic cost
low
high
low
low
Type of signal
Each channel of communication has different features
Knowing these features, and a species’ life history, one can make specific predictions about the communication signals on which a species should rely most heavily
e.g., wolves, moths, fish in deep sea vents, howler monkeys
Some signals are “honest” (i.e., convey accurate infromation), whereas others are “deceitful” (i.e., convey
inaccurate information)
Male Australian antlered flies possess bizarre “antlers” that are
thought to serve as a signal to other males, indicating their size
The antlers are said to be an “honest” signal because they accurately reflect each male’s size, and hence potential fighting ability
female 2 males
The functional significance of this signal is that it enables a male to avoid a fruitless and potentially dangerous fight with a larger male
During the breeding season, red deer (elk) stags engage in male-male competition. Instead of initiating potentially dangerous fights, they stand off at a considerable distance from one another and roar at each other.
This is thought to be an “honest” signal because the roaring is a physically demanding activity.
Only the most healthy and fit stags can roar for hours on end.
In most cases, females mate with those males that win the roaring contests
Female fireflies are the femme fatale of the animal
world. They use their abdominal flasher to attract
conspecific males for mating and heterospecific males for
nourishment.
A “deceitful” signaler
Unmated% of responses
Mated% of responses
Femme fatale eating heterospecific male
Unmated females responded most often to conspecific males, whereas mated females responded most often to heterospecific males
Courtship calls are often essential for attracting potential mates
Male Tungara frogs make this “chuck”call continuously over many hours to attract females
Some bats specialize on malefrogs during the mating season,
using their mating calls to locate them
This calling behavior, however, may be exploited by “illegitimate
receivers”
Vervet monkeys emit distinct alarm calls in response to the detection of 3 different types of predators
Notice that the othermonkeys in the troop respond to each alarm call in distinct ways
Two contrasting explanations of the Vervet monkey alarm calls
Meaning hypothesisMonkey produces asemantic signal for
leopardThe leopard call “stands for” or “conjures up imagesof” a leopard even before the monkey has seen the predator, and elicits an adaptive escape response
Acoustical propertyhypothesis
Monkey exhibited its loudest and longest alarm call because the threat posed by the leopard was so
great
The 3 different alarm call types reflect differing degrees of fear or excitement--that elicited by a leopard was the most intense and thus elicited the most dramatic response
How can we determine whether the monkeys areresponding to the acoustical properties or the meaning
of each alarm call?
Approach 1Vary the caller’s apparent level of excitement during a particular
call by altering tape recordings of the call (e.g., make the snake calllonger or shorter, louder or softer). Then observe the responses
of monkeys to these recordings.
Human example would be to pronounce “physical therapy” with two dialects: midwest vs. southern
When Cheyney and Seyfarth ran the experiment, they found that response of the monkeys to different pronunciations of the same
call did not change
What results would you predict based on the acoustical property hypothesis? The meaning hypothesis?
The Chutter call is produced when an
encounter between vervet troops has
escalated into aggressive threats
The Wrr call is produced when an individual vervet spots an approaching troop of vervets
Approach 2In the English language, “treachery” and “deceit” have same meaning
but different acoustical properties; in contrast, “treachery” and “leachery”have similar acoustical properties, but different meaning.
Cheyney and Seyfarth found an analogue to “treachery” and “deceit’ inthe vervet alarm call vocabulary:
Prediction: if these alarm calls have similar meaning to the vervets, then habituation to the Wrr call should generalize to the Chutter call
Note: this test employs a habituation-generalization paradigm