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I notice that this answer seems to rely on “group selection.” Of course, “individual selection,” a la Richard Dawkins is all the rage now. How would such colorings evolve in an individual selection paradigm?
And the link is: http://www.straightdope.com/mailbag/maposematic.html
Well, we can look at it at the level of the gene (a la Richard Dawkins). Imagine a whole family of colored insects. If one sibling dies to teach a bird not to eat that color insect, then the rest of the family will have a better chance at survival, since that particular bird will now avoid them all. The family members will have the same genes as the sacrificial member, so the gene overall has gained an advantage.
Probably we draw honey bees black and yellow because they are confused with yellowjackets. Which is probably why they tend to be both vicious and multiple stingers in the cartoons…
Save electrons, hm? Takes you more time to whine about colour. 
So tigers and zebras are presumably poisonous, too? <grin>
– Bob
Now, Bob, let’s not fall into that logical fallacy trap. “A implies B” does not mean “B implies A.” Common error in logic.
Doug said: If an animal is poisonous, then it has bright coloring (generally black and yellow or black and red). That is NOT the same as saying “if an animal has black and red markings, then it is poisonous.”… and, indeed, is the whole point behind protective mimicry.
I was told repeatedly in genetics class that random, spontaneous mutations must confer an immediate survival advantage on the organism for the mutation to spread and help the organism outcompete it’s close relatives who are not so gifted. If protective coloration was already an established event in the animal world I can see the value of a non-poisonous insect developing a brightly colored pattern (a la Batesian mimicry). But consider the first poisonous insects. They develop a bitter, even poisonous taste. Odds are, they would look much like their brethren and animals preying on them would have no idea they were any different based on their appearance alone. They would be eaten at roughly the same rate as the non-poisonous examples of their species. So any protection arising from their toxic status would extend to the drab species as a whole, as animals said to themselves “Better not eat that kind of butterfly, they taste like crap.” On the other hand, there would also be insects randomly developing brightly colored patterns that would cause them to get spotted and eaten immediately, stopping their genetic lines cold. Unless one mutation caused both the poisonous state and the bright coloration simultaneously, it seems very unlikely that both would arise in the same generation. So how on Earth would an insect develop the poison, which would eventually warn predators away from the species as a whole, and then develop a different, brightly colorated appearance to advertise that fact? It probably would not happen the other way around. As we’ve seen from numerous examples, any bright, easy-to-spot mutations usually get eaten so quickly, they have no impact on the gene pool. Wish I had some theories to offer, but this question has bugged me for some time.
DerIgel
I ain’t no expert here, but it seems to me that there are two possible scenarios.
First scenario: The first butterfly (say) to have a mutation that gave it a bitter taste didn’t actually have a major breeding advantage. It just lucked out and managed to survive, breed, and carry on it’s trait. So that after a while, there were some butterflies with a bitter taste and some with not, and the predators couldn’t distinguish. Then, the first butterfly with a bitter taste who also got bright colours, THAT was the competitive advantage; and the same-family guys without the bright colors got left behind in the evolutionary stream.
Sort of like, with people, eye color does not give a particular advantage or disadvantage to an individual. However, imagine that at some point in early stages, someone with blue eyes ALSO developed a third eye in the back of his head, that gave a huge survival advantage. Then, after much time, the people with only two eyes (and also those with non-blue eyes) would drop out of the gene pool.
Scenario 2: Not a single mutation, but a series of mutations, leading to worse and worse taste and to brighter and brighter colors, sort of alternating.
There is another alternative to “group selection” and “individual selection,” as Smeghead (really?) correctly pointed out and succinctly explained, although he (?) didn’t use the term itself. It’s “kin selection.” Since individuals in the same family share many of the same genes, a gene can be favored by the “sacrifice” of one individual, if its relatives receive a compensating advantage. So its OK if a bird eats your brother, as long as by doing so it learns to avoid you and the rest of your sibs. Kin selection is actually a much better established principle than group selection (which properly pertains to unrelated groups).
One critical aspect that the two previous posts overlook is that many animals, particularly insects, pick up the toxic principle from their food. Plants (evolutionarily) develop toxic “secondary compounds” in order to prevent insects and other herbivores from eating them. Some insects eventually (through selection) develop the ability to deal with these toxins and happily chow down on plants that are deadly poisonous to all other animals. As an added benefit, they may sequester the toxins in their tissues and so become toxic to their own predators. Under these conditions, development of aposematic coloration is a breeze.
The classic example of course is the Monarch Butterfly, whose aposematically-colored caterpillars feed on toxic milkweeds and sequester cardiac glycosides. The adults, although they don’t feed on anything poisonous, retain the toxins they picked up as larvae, and both caterpillars and larvae will make a Blue Jay puke its guts up. However, if you feed the caterpillar on something non-toxic, it won’t be poisonous and neither will the adult. In this case a naive Blue Jay (one that has not previously learned to reconize the warning coloration, e.g. one raised in captivity) will happily chow down on the caterpillar or butterfly without ill effects.
Aposematic coloration is also easy to explain in animals that are dangerous for other reasons, e.g. venomous snakes. They have venom (actually toxic saliva) basically in order to subdue their own prey, but this alos makes them dangerous to potential predators. So they may warn them away either with bright colors, such as coral snakes, or by warning sounds, such as rattlesnakes.
Interesting point, although meant facetiously. The animal of course doesn’t have to be toxic or foul-tasting, just dangerous in some way. SDStaff Doug’s answer focused on toxic critters and didn’t make much mention of those that might be dangerous in other ways.
Tiger coloration of course is primarily for camouflage. Although it COULD have a warning function, that’s probably superfluous. And animals probably wouldn’t have much chance to learn to avoid it.
Zebra coloration is often explained in terms of disruptive patterning, in that it supposedly breaks up the outline and makes them harder to see, but in my experience that’s horsepucky, as you can actually see zebras miles away across the Serengeti. It could, though, be warning coloration, as zebras kick and bite like hell and can on occasion do in a lion (doesn’t seem to deter the lions much, though). In my book, more likely it’s related to “social signalling” between the zebras themselves to keep the herd together.
And the black-and-white combination is often directed at mammalian predators, which generally lack color vision; or occurs in nocturnal animals, since colors are difficult to see in low light. Case in point, the skunk.
The Giant Panda is an interesting case, as it is a slow moving and generally placid beast that might seem to be fair game for a tiger. However, they have massive jaws and can deliver a powerful bite, and the distinctive coloration may in fact signal predators that they are not to be trifled with.
Here we have an interesting display of the TWO methods by which disruptive coloration works. The tiger being a loner and indigenous to forested areas wants to hide thus the disruptive coloration ala camouflage. Now the zebra is almost never found alone and is for many parts of the year found on open grassland. Unless you count the occasional Masai warrior, there’s not much to hide behind. Their disruptive coloration isn’t meant to hide them so much as confuse the enemy so to speak. As the group bolts under attack, Ms Lioness can’t see where one zebra starts and the other begins. Chances of a well aimed attack within the herd are slim. Rather than rushing willy-nilly into the wrong end a zebra (who can BTW inflict serious damage), the hunting parties almost always chose their dinner from outside the pack or separate the herd before pouncing.
Nice try, gonz, and maybe better than the “camouflage by disruption one,” but is there actually any evidence for this? I might consider it if the lions actually used a different hunting technique for zebras than they do for other herding animals, but as far as I know they don’t. They’ll use the same technique of singling out an isolated individual when hunting gnus as when hunting zebras. And unless there’s some sort of difference, I don’t think you have a case. The predator-confusion argument is often used to explain herding behavior in general; but it works pretty well for dull colored animals as well. And can you offer any other examples of herding/flocking animals in which this kind of coloration occurs? It should be more widespread if this works.
I haven’t tried to look this up (yet), so I am BSing here as well, but zebras, as members of the horse family (equids), could well have a quite distinct social system from most of the other herding animals of Africa, which are mostly in the antelope/cattle family (bovids). The variation in striping pattern also offers the possiblity of individual recognition over distance, assisting in the cohesion of social units (harems or family groups).
Thanks for the kind words Colibri-
You are correct in that hunting technique is pretty standard regardless of coat type, and it may have more to do with ease of pulling a single animal down without worrying about being trampled. However, pattern disruption in groups is a fairly well accepted theory. Its often used to explain tight schooling behavior is open-water fish when threatened. It makes it more difficult to isolate and focus on a single individual.
Also, if I remember correctly, athough herding behavior is fairly standard among african grazers respone to predators is not. Antelope tend to scatter- sort of every man for himself. This also gives them room to ‘stot’ or basically show-off their fitness; being buff-colored they could also blend into the savannah. Zebra, on the other hand, tend to remain grouped enhancing the striped effect. I also seem to remember reading somewhere about zebra patterns as of benifit in tall grasses.
As for the stripes being a warning, I kinda doubt it. 1st it dosen’t seem to deter predators from attempting killings. Secondly, several of the larger antelopes come standard equipped with very nasty-pointy horns,which they use quite effectively to mame or kill predators. Many are considered more ‘dangerous’ than the zebra and although some are quite beatiful, none have what would be considered warning colors.
Thanks for the kind words Colibri-
You are correct in that hunting technique is pretty standard regardless of coat type, and it may have more to do with ease of pulling a single animal down without worrying about being trampled. However, pattern disruption in groups is a fairly well accepted theory. Its often used to explain tight schooling behavior is open-water fish when threatened. It makes it more difficult to isolate and focus on a single individual.
Also, if I remember correctly, athough herding behavior is fairly standard among african grazers, respone to predators is not. Antelope tend to scatter- sort of every man for himself. This also gives them room to ‘stot’ or basically show-off their fitness; being buff-colored they could also blend into the savannah. Zebra, on the other hand, tend to remain grouped enhancing the striped effect. I also seem to remember reading somewhere about zebra patterns as of benifit in tall grasses.
As for the stripes being a warning, I kinda doubt it. 1st it dosen’t seem to deter predators from attempting killings. Secondly, several of the larger antelopes come standard equipped with very nasty-pointy horns,which they use quite effectively to mame or kill predators. Many are considered more ‘dangerous’ than the zebra and although some are quite beatiful, none have what would be considered warning colors.
Ok, gonz, points well taken, and on some of them you may be right. I’ll address them in order.
Paragraph 1)
Now that I think of it, I think you’ve got a point about the fish. Some schooling fish such as mackeral are striped, and this could also be the explanation for the silvery color of many species, which might confuse and dazzle the attacker. But schooling fish move in a much more coherent and coordinated fashion than a herd of zebras, which would enhance the effect. Also, for herding mammals, I would continue to question why, if this is such a good strategy, it doesn’t seem to occur in anything else but zebras.
Paragraph 2)
Ok, if this is in fact true it’s the sort of factor that could make a difference. However, while it could be true for some antelope I doubt that it’s true for all of them, particularly for gnus/wildebeest, which are fairly close to zebras in terms of size. And staying in a herd will be advantageous for most antelope, exactly because of the sort of target-confusion factor you mention. (Note that I am not disputing that herding behavior in general doesn’t help to confuse predators, by providing them with “too many” targets at the same time; just that I don’t think that predator confusion is adequate to explain the difference in coloration between zebras and other herding mammals.) But with all due respect, I think both of us are just BSing here. (If you actually have specific info mention it). What we need is some facts. (And the tall grass point I think would apply to the disruptive coloration hypothesis, not the predator-confusion one).
Going an a tangent, I want to say it was generally a good column, but
I think that goes a little far. We use black on yellow signs because it stands out. But we also have warning signs in red on white, white on red, black on red, and recently I have seen “Caution: wet floor” signs in black on pink. I don’t think the color selection is instinctual, but just a matter of sense. What stands out? Good color contrast. Yellow typically stands out better than white from surroundings. It’s different.
As for honeybees - I think maybe the reference to yellow-jackets is more appropriate. Someone colored a bee black and yellow, and taught it to everyone else, and the rest of us duplicate that and do it that way because “bees are black and yellow”. Same as the onomatopoeia of animal noises. Cows going “moo” and dogs going “bow wow”. Real animal noises only vaguely sound like those words, but we’re all taught those specific sounds as kids.
Now the zebra is almost never found alone and is for many parts of the year found on open grassland. Unless you count the occasional Masai warrior, there’s not much to hide behind. Their disruptive coloration isn’t meant to hide them so much as confuse the enemy so to speak. As the group bolts under attack, Ms Lioness can’t see where one zebra starts and the other begins. Chances of a well aimed attack within the herd are slim. Rather than rushing willy-nilly into the wrong end a zebra (who can BTW inflict serious damage), the hunting parties almost always chose their dinner from outside the pack or separate the herd before pouncing.
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Nothing like the facts:
In his article entitled, “The Zebra’s Stripes: An Aid to Group Cohesion?”, Jonathan Kingdon, the leading authority on African mammals (pages 486-487 in “The Encyclopedia of Mammals,” 1984, edited by David Macdonald, Facts on File Publications) states:
“The visual theorists try to imagine the effects of stripes on pests and predators. One ingenuous [sic] explanation has it that charging lions are unable to single out an individual because it merges with others in the herd; another suggests that the lion is dazzled or miscalculates its imaginary last leap. These theories founder on the observable confidence with which lions kill zebras and on the fact that . . . zebras are killed broadly in proportion to their relative abundance.”
(No offense to you, gonz, but note that Kingdon says this theory is ingenuous - “naive” - rather than ingeniuos - “clever.”)
Kingdon goes on to discuss, and dismiss, alternative explanations, including camouflage, pest (biting fly) avoidance, and heat regulation. He makes a very strong case that stripes are a social signal that serves to promote cohesion within the herd. Interestingly, zebras seem to be innately attracted to stripes. I will not attempt to summarize Kingdon’s detailed arguments here, but refer you to the article itself.
As an interesting sidelight, it appears that stripes may be a primitive characteristic within the Equidae (Horse Family), and that the ancestors of domestic horses and donkeys may have been striped like zebras. Zebras are thought to be closer to the ancestral form.
Latter should be ingenious of course.
First thank you everso for point out the ingenuous point.
Secondly, although this guy may be an ‘expert,’ unless his ‘opinions’ are backed by research they are still simply opinions:
1st you are correct in that stripes are considered a primitive trait in Equidae, and they occassionally pop-out in modern species. Secondly as for group cohesion, I could not find one article in support of this-- mainly, I think, because it is almost impossible to test. Also Zebra herds are essentially the same as all other Equidae. Somehow these other herds maintain similar group dynamics and cohesion without the benefit of stripes.
Now for the facts:
As to the predator confusion: Again, this is terribly hard to test but,
Holekamp, et al. (Journal of Zoology, vol. 242 no. 1 pp 1-15, '97) note that in spotted hyenas over 75% of hunting attemps are made by lone animals, even with targets 3 times their body mass i.e. wildebeast, topi (stuff zebra size). Of commonly hunted animals ONLY zebra were hunted with the help of the pack as a rule. Cooper et al. (Afrian Journal of Ecology, vol 37 no. 2 pp 149-160 '99) notes that zebra are not the ‘preferential’ target of hyenas.
Funston et al. (Animal Behavior, vol 56 no 6 pp149-160, '98) note similar findings for lions. Lone animals, essentially male, choose buffalo as their main target. Only groups of females will consistently target zebra.
These tell us either that zebra are really nasty to take on in a head-to-head fight, or that some group dynamic is needed to effectively target a zebra herd. As for the former, I cannot imagine anyone who would claim a zebra is tougher than an african wild-buffalo. I don’t know if the latter makes a case for predator confusion or not.
Finally, I think the clearest case for stripes is made by Gibson in Physiological Entomology, vol. 17, no. 2, pp 141-147. Using some rather unique studies, (s)he found that the particular orientation of stipes on a zebra attracted less than 10% of the tsetse flies as expected for solidly colored, patterened, or a differently striped animal.
Obviously stripes convey some advantage to the male herd-master, otherwise different patterns woud have arisen. Due to zebra’s social structure, stripes cannot be due to female-selection.
OK, I am will plead ambiguity about the predator confusion, but I am now firmly behind… fly camouflage!
I do apologize for the rather brusque remark about Mr. Kingdon’s career. I’m sure he is a perfectly lovely expert.