the evolution of communication chapter 9 or you did not just say that?

The Evolution of Communication

Chapter 9

Or

You did NOT just say that?

Definitions of CommunicationTinbergen, 1964:One party - the actor - emits a signal, to which the other

party - the reactor - responds in such a way that the welfare of the species is promoted (adaptationist view)

Smith 1977:Displays are acts specialized to make information

available.

Wilson, 1975:An action on the part of one organism that alters the

probability of a pattern of behavior in another organism in a fashion adaptive to either one or both of the recipients.

Slater, 1983:The transmission of a signal from one animal to another

such that the sender benefits, on average from the response of the recipient.

An Origin of Signals

Basic Idea: Preexisting perceptual (sensory) mechanisms bias the evolution of signals.

Signalers “exploit” sensory bias in receivers of signals.

Now some examples of Sensory Exploitation

Water mitesMales uses leg to mimic food to trigger

food detection in female.

When female determines that she has grasped a male and not food, she mates with him.

Tungara Frog

Capable of producing a whistle, whine, and chuck call.

Chuck is the call females most prefer.Females will approach chuck calls

However, chucking also attracts bat predatorsThey key in on the multi-frequency chuck call.

Prediction on Use of ChuckingChuck if you can’t find a mate Not testedIf you see a bat, stop chucking YesIf in a small group, chuck less often (Why?)If in a large group, chuck away

Note – frog alarm calls signal for stop calling (the watchman’s song)

ChuckingThis is the only species that “chucks”

However, all females in clade prefer chucking.Preference for chucking appeared before actual

chucking.

Why did this preference occur?Probably had some function other than mate

choice.

F F Tungara Fchucking

Chucking preference in females

Swordtail

Females choose males by length of ray

All females prefer swords, although swords only appear in 2nd half of group.

Why do ravens scream their heads off when they find a carcass?

Costs to yellingAttract predators

Attract competitors

Possible Hypotheses

Attract a larger animal to open the carcass for them.

Attract other ravens to defend against predators

Gang-up on territory owner

Testing

Predict: Open a carcass yourself, and they get quiet.

Observe: they still yell

Predict: stop yelling once a certain number of ravens reach site.

Observe: keep screaming, even in large groups.

Gang warfare

A large number of intruder ravens can overcome a territory owner of a carcass.This allows intruders to feed

Predict: owners don’t yellObserve: owners never yell

Yelling attracts other intruders

Benefit = getting to eatCost = having to compete with others.

Singing as a Signal in Songbirds

Two Hypotheses (for male singing)

Attract mates

Repel other males

Attracting FemalesPredictions

Sing around females Yes

Sing in the breeding season Yes

Sing complex songs to attract more femalesCapable only by older, more experiences males in breeding

Stop singing once mated Yes and No

Repel Other Males

PredictionsSing in presence of males, with more singing for greater

intruder presence YesIf you silence a male, intruders should increase YesFewer males intrude a tape than when silence.

Mate guardingSinging can also serve as a way to protect

paternity

BackgroundExtra-pair fertilization of eggs is common.Females of numerous species may seek other

malesIf males can run other males off, then hopefully,

the eggs in the nest are his.

Whose bed have your boots been under?

Assumption

Singing conveys information about male quality or ability to guard female.

Predict:

Males sing when mate is most fertile (a day before laying). YES

Males in better condition sing more. YES

Intruder frequency will decrease when song quality increases Untested to date

Signalers and Receivers

SignalersIndividual that sends the signal (visual, sound, etc.)

ReceiverAny animal that can detect the signal

Does NOT have to be the intended receiver

How can spiteful signaling be naturally selected?Hurt another to put them worse off than yourself.(end of semester)

Incidental Receivers

Biggest problem incidental receivers are predators

Tungara Frog and Fringe-lipped BatWhen frog chucks, it is using a location call

(multi-frequency)

Bats can home in on this and strike

Bird alarm calls

Typically use calls that are hard for predators to detect. (seet call)

Minimize the risk of warning by not drawing attention to yourself.

Deceitful signals

Fireflies and lighting bugs

2 species: Photuris A and B

Form cooperative signaling by males to females

“mutually beneficial”Don’t mate with the wrong species

So what’s deceitful?

The Deceit

Male B’s respond to specific flashing patterns of female B’s.

Female A’s mimic female B’s response to male B’s.

Female A’s are predators on male B’s.This is selected caution in male B’s.

Female A’s are only successful about 10% of the time.This selects for better mimicry in A’s.

Deception by Chickadees

If a lot of birds are at a feeder, and the Chickadee can’t get any food, they sometimes give false alarm calls to everyone to hide.

While the dominate larger birds are hiding, the Chickadees gets a quick meal.

Tanager-shrikes do the same thing to get competitors to stop chasing insects they want.

Displays, deception and “honesty”

Fact – Many animals settle disputes by ritualized displays.

Animals actually rarely fight, too dangerous.

A certain display is usually all that is needed to see who wins and who losses.

So why not fake the winning display or signal?

Truth in sound

Many of these signals are “honest” and can’t be faked.

Only bigger toads can make deeper calls

Truth in sound IIRemember roaring in elk?Must be in good shape to roar for a

period of time.If that doesn’t settle it, then a side-by-

side assessment will determine.Only under same roar and same size will a

fight occur.