So wait, you’re telling me that zebras and maybe giraffes are bar coded? Totally froody.
OTOH, don’t humans have pretty awesome color vision compared to most mammals? Is it possible we’re seeing more than their predators?
OTOOH, there’s no real reason to assume an either/or case. Camoflage may have arisen when giraffes were smaller, and morphed into a social purpose as they outgrew their predators, if I’m not mistaken.
Case in point - there are 27 giraffes in that second link.
True; it’s well-known that the stripes on a zebra aren’t apparent when viewed in black-and-white.
Colibri said:
Perhaps, but when I look at that photo, I see
a) background leafy and woody debris in shades of brown
b) limbs and the like in grayish brown
c) ground in light grays and tans
d) bushy tan grass stalks
Basically the color mix of the coats shown. Particularly noteworthy are the patches of tan that look very much like patches of grass. I think their color scheme and patterning is ideal for camoflage in the area they hunt.
Wait, couldn’t this simply be a matter of divergence through isolation? Populations separate, get slightly different gene drift, markings look somewhat different from different groups, but look similar within that population? Kinda like human populations and how East Asians look different than South Asians look different than Caucasians?
ianzin said:
And how would you go about determining if there is a purpose? Other than proposing possible purposes and then evaluating how the pattern fits with that proposed purpose?
Maybe the camo works better when the giraffe is prone and more vulnerable to attack.
Yes, humans have three kinds of color receptors. Giraffes, lions, and most other mammals have only two kinds of receptors, and so see a much more subdued color pattern.
It could have some limited function in that way, but wild dogs are pursuit hunters, not ambush hunters. They are normally going to be very apparent to their prey while they are hunting, and don’ need to be camouflaged.
That’s exactly how such differences probably came about. However, features that are under selection by the external environment are going to be constrained to vary comparatively little, or else to vary in concert with differences in the external environment. In contrast, features maintained because of mating or social interactions have no such constraint - they can vary in any direction. In fact, this is exactly the kind of variation we see in things like courtship plumage, bird songs, and other features in isolated populations.
In some sense, the answer to that is always, “No”. Evolution doesn’t have a goal in mind, it just tries random stuff and whatever works – or at least doesn’t harm the animal – persists. Minus two (or more) separate populations in the same exact conditions, where some evolve and others don’t, answering what bonus the changes to the species had (if any) is pure guesswork, no matter how well-reasoned it may be.
One might guess that the pattern formed when giraffe were smaller, as camouflage, and then stuck around as they grew because it didn’t harm them any, or that it is and always was for social identification, and/or a bit of flash for attracting mates. Since there’s no logical force in operation, it’s very hard to say whether an adaption is as a result of something, or simply happened and any use it may have is as a result of the adaptation happening in the first place.
I’ve had the same experience in Tanzania. We would stop to look at the giraffe way over there, in the open, and eventually reallize that there were 5 or 6 of them standing much closer to us, but in some trees or shrubs. I’ve got a picture that we took of 2 giraffes a ways off. Only after we got home and had it developed did we reallize that there were several others in the picture as well.
It seems like you’re almost saying that the term ‘purpose’ is meaningless, but I don’t see why it should be. Sure, Evolution has no goal. Sure, we don’t know exactly how feature X came to exist, but that still doesn’t mean we absolutely can’t identify what it does - and that’s what ‘purpose’ means here.
[quote=“Mangetout, post:29, topic:550457”]
Using the term ‘purpose’ can be confusing in these discussions, and it does not help people understand evolution better. On top of that, the ‘what it does’ is often based on limited information about the evolutionary history of the animal, and is highly skewed by human perceptions and biases. Giraffes may have inherited their coloring from ancestors that gained an advantage from it, that no longer exists for the modern animal. Giraffes are very big, and probably easily spotted (groan) when they move. So camo doesn’t seem to be a big factor, but modern giraffes may have evolved in an environment where the patterns were very effective camoflage in hiding from the local predators. The patterns may be related to sexual selection, and identifying populations, or all giraffes may have Far Side type thoughts about they wished they didn’t have all those freckles. The pattern also might be a side effect of the genetic structures that gave them a long neck. It’s obvious that predators have teeth for killing prey, and firemen wear red suspenders to hold up their pants, but many innate attributes are very difficult to ascribe to a specific use or advantage.
It’s worth noting that many features do nothing, but are “side effects” of something that does. For example, nipples for men. IIRC, these appear developmentally before the fetus’s gender develops. So they remain on men as a side effect of the order of development, and because they are useful in women.
It could be, to completely make something up, that a giraffe’s skin gets tougher to resist biting flies and a side effect of that toughening is a mottled fur color. Or it could be that the mottled color serves a useful purpose to the tick birds that themselves serve a useful purpose to the giraffe – but if so, examining giraffes in a lab will never reveal that, because you’d be missing the tick birds. Evolution is tricky and “purpose” is murky.
Ah, on reading more closely, I see TriPolar said much the same thing, even using “side effect” the same way. 
The problem with thinking in terms of “purposes” is then you get people saying things like homosexuality can’t be genetic because it serves no evolutionary purpose, ignoring that poor vision, sterility, autism, being intersexed, etc. are all genetic (in instances) and certainly don’t aid in propagating the species. Lots of stuff occurs and persists regardless of purpose because evolution isn’t actually being guided by some all-knowing hand. It just toggles random levers in a DNA strand and if that causes a malformed creature that doesn’t even survive to term, that doesn’t mean that the next attempt won’t also be a similarly malformed creature.
However, none of the characters you mention occur in most individuals of the species. The giraffe’s color pattern occurs in virtually all members of the species, which implies that, no matter how it originated, it is being maintained in the population by some kind of selection (whether by predation, or for social reasons, or for some other reason). If it wasn’t under selection, you would expect a greater proportion of individuals not to have it - as for example in the increased frequency of black and white morphs in urban squirrel populations where predation is reduced. It is reasonable on those grounds to ask what are the factors that maintain this pattern in the species across its entire range. It is very unlikely that this kind of complex pattern is maintained merely due to some kind of “evolutionary inertia.”
Yeah, it was just a caution. A better example for a human analog would be the shape of our bald/haired spots, probably?
So we don’t have to clean them as often.
Colibri said:
I certainly get that.
Well, I don’t see a wide variance in the coat patterns of different giraffe groups. They all are essentially orange blotches patched in a bed of tan, or alternately a webwork of tan on an orange backdrop. What varies is the size and jaggedness of the blotches. The colors aren’t different, merely some minor distinction in the kind of shapes of the pattern. In fact, there’s less variation across the subpopulations than there is across individuals of African Wild Dogs. It doesn’t seem like a lot of variation to me.
In my opinion as a biologist, there’s more variation than would be expected if the trait was being maintained by selection by camouflage against predators. The variation seen is likely to make the animal more or less visible against a background of trees, so there should be some stabilizing selection to maintain an optimal pattern. If you look at the third and fourth patterns in the link, there is quite a lot of difference in the balance between dark and light areas, the width of the light areas, and so on, even though these two patterns occur in adjacent populations that live in fairly similar environments. It’s unlikely that those differences would have been created or maintained by selection by predators.
In contrast, if the pattern facilitates social recognition, it doesn’t matter exactly what the pattern is, as long as each individual is recognizable (which is also the case in Wild Dogs.)
I would have assumed (having looked no further into this) that African Wild Dogs would rely more on scent than sight for recognition. They aren’t domestic dogs, so the behavior may be different, but I’ve noticed domestic dogs that act apprehensive when they see a dog that they know, until the dog gets close enough to smell (or perhaps they were just near-sighted dogs). I think it matters in relation to how the mechanism works. Camouflage is more passive. The pattern only has to make the animal less apparent to predators. But as a means of recognition, the brain function to recognize the pattern comes into play. Since giraffes seem to maintain segregated sub-populations even when they live in proximity, it would seem like that brain function is strong in giraffes.
IANA biologist, but your comments seem logical based on the information I have (which is not a lot, my interest in giraffes is due to the ‘radical’ idea that giraffes don’t have long necks so can feed in the tree tops).
As canids, no doubt the sense of smell is important in individual recognition. But if each individual is distinctively marked, it can be recognized by other members of its pack even at a considerable distance and when the wind is in the wrong direction. They hunt by sight and in daylight, so sight may be particularly important to them; as cooperative hunters it may be important to recognize other individuals at a distance. Also, the species has a more complex social system than other canids. Usually only the dominant female has a litter each year, the other pack members cooperating in raising it.
True, that. Ships painted with dazzle camouflage were anything but hidey but the patterns made it difficult to tell whether they were coming or going, or moving from left to right or vice-versa.