1. Honest Signals

2. Confusing Signals Communication ought to be adaptive
Attract mates
Scare off intruders
Advertise fitness
Warn of predators
Not always obvious to scientists what the value of certain signals is
Why would maladaptive signals be maintained?
Fitness of signal giver and signal receiver

3. Honest signals
Honest signals are adaptive because they can’t be mimicked. If they are mimicked, receivers can learn to ignore the fake signal, reducing the likelihood of it being produced.
Hypothesis: Threat signals are honest signals that accurately reflect a male’s capacity.
Predict that sick or weakened males should not be able to produce as robust an ‘honest’ signal of aggression compared to their healthy state.

4. Threat displays require energy

5. Judging the honest signal informs the decision to attack or not
The male croak is an honest signal—physics and body mechanics prevent it from being otherwise. True of certain geckos and owls as well—lower frequency means larger size.

6. DQ
The reason why so many species resolve their conflicts via mostly harmless threat signals is to reduce injuries and preserve the health of the breeding adults who are needed to produce the next generation.
What is the problem with this hypothesis?

7. What are the advantages?
To losers: save energy by not fighting an unwinnable fight
Imagine if aggressors fought everyone they encountered. They would be exhausted and depleted. Furthermore, they would be defeated.
Aggressors that walked away from superior opponents would be less likely to be defeated and conserve energy.
To winners: conserve time and energy.

8. Illegitimate Signalers
Illegitimate signalers reduce the fitness of the receiver through their deception
Orchids that lure male wasps into attempts at mating with the flower
Femme fatale firefly
Responds to male of different genus
Illegitimate receiver
Replies with species typical flash
Illegitimate signaler

9. Deception poses a problem for adaptationists
The maladaptive behavior was once adaptive but is no longer. Modern conditions are different and not enough time has passed for advantageous mutations to “fix” the problem
The maladaptive response reduces the fitness of the signal receiver but not enough to negate the fitness gain from reacting to the signal in the particular way.
Examples of each?

10. Angler fish uses the “bait” hanging off its head to attract smaller fish that it will eat as they approach
Deception evolves because the loss of fitness to receivers of illegitimate signals is not complete, whereas loss of the ability to respond to the signal (mate for firefly, food for fish) would result in zero fitness

11. DQ
Develop an honest signal hypothesis AND a deception hypothesis to account for the following observation.
Male butterflies (and other insects) will transfer a substance to their mates that makes the females sexually unappealing to other males.
How could you figure out which is correct?
Honest—once female has mated, she is unable to use another male’s sperm and is truly unappealing
Deceptive—once female has mated, she is willing to mate with other males and can utilized the ‘best’ sperm to fertilize her eggs

12. Fringe-lipped bat as an illegitimate receiver
Male frogs tend to only use the whine-chuck combo when the risk of predation is low, such as when the location can be diluted by many other males singing at the same time.

13. Illegitimate receivers
Uses the signal information to the detriment of the signaler.
Crickets in Kauai (Hawaii) went from calling to silent in 20 generations after a deadly parasitic fly was introduced.
Alteration to wing structure characterizes silent males

14. Evolution of Signals
The great tit makes two different calls in the presence of a predatory hawk. The mobbing call is used on a perched hawk and serves to attract others to harass the hawk. The seet call is used when a great tit sees a flying hawk and can be used to warn others without alerting illegitimate receivers including the hawk to their locations. This is due to the different frequencies of the calls—the seet call falls outside of the hawks best hearing range.

15. Evolution of the seet call
Pressure by bird eating hawks has led to the adaptation of a high frequency alarm call that falls out of the range of the predatory hawks in many unrelated species of songbird.

16. A Maladaptive Signal? Ravens observed calling/yelling at a carcass
All in the same family?
Attract a carcass opener?
Get other ravens to dilute a predator threat?
Gang up on territorial pairs?
Predictions of this hypothesis?
Residents should not yell, non-residents (singles) should yell
Yelling should recruit additional nonresidents to the carcass
Resident pairs should not be able to repel intruders
Food ‘bonanza’ should be eaten by resident pair or yelling mob

17. Data collected supports the “gang up on territorial residents"

18. Why do baby chicks beg? Baby chicks produce robust begging calls
Is this adaptive?
It attracts predators (29/37 eggs taken from a noisy nest vs a silent nest)
Frequency modulation attenuates risk (high frequency doesn’t travel as far)
Parental warning calls eliminate begging calls from chicks, reducing their risk

19. Nest raiding

20. Frequency modulation in warblers

21. But why beg at all? Sibling rivalry? Honest Signal Hypothesis
Gain parents attention, get more food
Honest Signal Hypothesis
Begging cries provide accurate info about need
Predictions of each?
Some overlap

22. Experiments to distinguish
Placing food deprived baby robins in the nest with well fed siblings led to more robust begging from the well fed babies.
Which hypothesis is supported?
Chicks with no siblings (Wilson’s storm-petrel) produce a begging call when the parent returns with food that is directly correlated with its physical condition (poor=more frequent calls)

23. Parental Response to Begging
Blue throat parents feed the largest (first hatched) baby first despite equal begging from smaller, younger chicks.
-Based on body size, not begging
But other species feed the loudest most intense caller and therefore do pay attention to begging.
Why don’t such chicks beg as hard as they can so that might secure more food?
Species with delay between hatching, first is larger, stronger, later chicks have more T in the egg, allow for stronger begging
Indirect selection: sharing food with siblings increases the likelihood of genes being passed on.

24. Reed Warblers Feed Beggers
Even when it isn’t her own offspring. Blackbirds don’t really beg a lot, but when a speaker plays the begging calls of the cuckoo (mimics a brood of 4 warblers—is an illegitimate signaler) or an actual warbler brood, the parents almost double the amount of food delivered.

25. Cuckoo can mimic the call of a brood of warblers
Cuckoo as an illegitimate signaler

26. Honest or deceptive signal??