A peacock that has to struggle to survive while dragging around a conspicuous tail is clearly at a disadvantage. But if he can continue to survive, then clearly he must be pretty strong! So the peahens may choose to mate with him rather than the peacocks with less conspicuous tails, whose survival is thus a less impressive feat.
I’m not sure that’s true. Wikipedia lists several competing theories:
Sexual selection, first proposed by Darwin himself in this case: he thought peahens preferred peacocks with bigger tails, and so bigger tails evolved, regardless of expense in fitness.
Costly signalling, proposed by Zahavi, as you describe.
Some studies listed by Wikipedia claim that peacocks with smaller tails suffer more predation (mechanism unknown), and that females prefer males with certain tail patterns (many ‘eyes’) rather than size.
Some other studies confuse everything even further by claiming big, erect, flashy tails serve to intimidate predators and evolved through ordinary natural selection.
Now, how would one test this? Especially considering that some theories mostly differ in their explanations of the evolutionary history leading to the present; they all match the present birds. I do know that real-life biologists sometime claim peacocks as archetypical evidence for sexual selection, and others claim it as evidence for costly signalling of fitness.
Sexual selection, first proposed by Darwin himself in this case: he thought peahens preferred peacocks with bigger tails, and so bigger tails evolved, regardless of expense in fitness.
This isn’t an explanation until it can explain why peahens prefer peacocks with bigger tails. That’s what the signalling hypothesis is for. I don’t see why these are considered competing hypotheses.
Sorry, should have made that an independent comment, not really an answer to anything in this thread. Just a pet theory brought to mind by all this talk of peacocks and signalling. Cats threaten each other with a toneless sound of rushing air, and and are afraid of high-powered mechanical devices that produce a version of the same effect.
A surplus of resources is one thing that can be signaled, and resistance to parasites is another. They both involve signalling, but these ideas are a bit different from each other—and from sexual selection, which can magnify a wide range of “fashionable” traits.
Of course those things are different from sexual selection. Comparing a trait that can be signalled, to a mechanism by which traits can be magnified, is a type error.
I’m not saying that “sexual selection” and “costly signalling” are the same hypothesis, I’m just saying they aren’t competing. One attempts to explain how a trait gets magnified, the other attempts to explain why.
It looks as though the post you were responding to was wrong to treat these as incompatible hypotheses.
No doubt, peackock tails are magnified by sexual selection, costly and illustrating parasite resistance. However, though compatible, these explanations do compete with each other a little—for example, when explaining particular features of the tails.
Some studies listed by Wikipedia claim that peacocks with smaller tails suffer more predation (mechanism unknown),
A predator which relies on vision for target identification might survivably assume that anything which appears large and flashy actually is physically large, with muscles and defenses to match, thus out of it’s league, and look elsewhere for prey. A wide flat tail with a colorful pattern is probably the most cost-effective way to maximize your apparent size, at least from the front and back.
I’m not sure that’s true. Wikipedia lists several competing theories:
Sexual selection, first proposed by Darwin himself in this case: he thought peahens preferred peacocks with bigger tails, and so bigger tails evolved, regardless of expense in fitness.
Costly signalling, proposed by Zahavi, as you describe.
Some studies listed by Wikipedia claim that peacocks with smaller tails suffer more predation (mechanism unknown), and that females prefer males with certain tail patterns (many ‘eyes’) rather than size.
Some other studies confuse everything even further by claiming big, erect, flashy tails serve to intimidate predators and evolved through ordinary natural selection.
Now, how would one test this? Especially considering that some theories mostly differ in their explanations of the evolutionary history leading to the present; they all match the present birds. I do know that real-life biologists sometime claim peacocks as archetypical evidence for sexual selection, and others claim it as evidence for costly signalling of fitness.
This isn’t an explanation until it can explain why peahens prefer peacocks with bigger tails. That’s what the signalling hypothesis is for. I don’t see why these are considered competing hypotheses.
Do you suppose a cat’s hiss tells another cat something about strength and fitness via lung-power?
That could explain their fear of vacuum cleaners and blow-driers.
I don’t suppose that, and I assume you don’t expect me to suppose that, but I don’t know what you’re trying to tell me.
Sorry, should have made that an independent comment, not really an answer to anything in this thread. Just a pet theory brought to mind by all this talk of peacocks and signalling. Cats threaten each other with a toneless sound of rushing air, and and are afraid of high-powered mechanical devices that produce a version of the same effect.
A surplus of resources is one thing that can be signaled, and resistance to parasites is another. They both involve signalling, but these ideas are a bit different from each other—and from sexual selection, which can magnify a wide range of “fashionable” traits.
Of course those things are different from sexual selection. Comparing a trait that can be signalled, to a mechanism by which traits can be magnified, is a type error.
I’m not saying that “sexual selection” and “costly signalling” are the same hypothesis, I’m just saying they aren’t competing. One attempts to explain how a trait gets magnified, the other attempts to explain why.
It looks as though the post you were responding to was wrong to treat these as incompatible hypotheses.
No doubt, peackock tails are magnified by sexual selection, costly and illustrating parasite resistance. However, though compatible, these explanations do compete with each other a little—for example, when explaining particular features of the tails.
A predator which relies on vision for target identification might survivably assume that anything which appears large and flashy actually is physically large, with muscles and defenses to match, thus out of it’s league, and look elsewhere for prey. A wide flat tail with a colorful pattern is probably the most cost-effective way to maximize your apparent size, at least from the front and back.