# Why no green mammals? (or blue) **URL:** \ **Category:** Factual Questions\ **Created:** [February 12, 2010, 6:02am UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671 "2010-02-12T06:02:08Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Kobal2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kobal2/32/20_2.png) [@Kobal2](https://boards.straightdope.com/u/Kobal2)\ **Post date:** [February 12, 2010, 6:18pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/21 "2010-02-12T18:18:07Z")
Here’s a [green polar bear](http://www.msnbc.msn.com/id/26591321/) for ya. (All right, so like the sloths, he’s cheating with algae. Still. Green bear.) ---
**Author:** ![constanze](https://avatars.discourse-cdn.com/v4/letter/c/f9ae1b/32.png) [@constanze](https://boards.straightdope.com/u/constanze)\ **Post date:** [February 12, 2010, 7:51pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/22 "2010-02-12T19:51:33Z")
> [@Markxxx](#): > > The reason I always hear given, since I was a kid in high school is that hair fades quickly and even if it grew in green it wouldn’t stay green for very long. And then it’d fade and the incoming hair would be green and you would have different shades of green and it would make the mammal different colored and more visable. That doesn’t sound plausible to me. If you look at a general camouflage uniform, it’s small patches, not a uniform shade. Broad shapes of one colour get you noticed sooner, not small irregular patches. So that would work in the animals favour. > [@](#): > > Same applies to any color and that’s why mammals are so dull colored. > > The color of skin is similar but also has other facts like blushing and collagen which accounts for some of the difference. > > I don’t really buy it but that is what my high school biology teacher told us when someone asked the question. Except for those mammals where sexual preference for a colour rates higher than hiding. I still would like to know how it would be biochemically possibly - that even birds cheat with light refraction, and that monkeys (if I understand the earlier posts correctly) aren’t really blue, but naked means that blue and green are almost impossible to produce with proteins. But why? Leaving aside the question of why it hasn’t happened yet, if some mad scientist wants to switch genes, or splice something into the human genome (like that terrible new Hulk movie, where at the beginning Banner puts in biolumincence as marker to “explain” why the Hulk is green), is there any way he could get it? How about incorporating a certain mineral or other element by food that in conjunction with an enzyme lets hair or skin look green or blue? We already have slightly blue blood in human veins, copper-based green blood in vulcans, and real blue blood in snails. ---
**Author:** ![umop\_ap\_sdn](https://avatars.discourse-cdn.com/v4/letter/u/dbc845/32.png) [@umop\_ap\_sdn](https://boards.straightdope.com/u/umop_ap_sdn)\ **Post date:** [February 12, 2010, 8:24pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/23 "2010-02-12T20:24:55Z")
I wonder something similar to that, why couldn’t chlorophyll be absorbed from plants and distributed to the skin or hair. IIRC don’t flamingos do something similar with the red pigments from the creatures they eat so unless it has to do with feather structure… ---
**Author:** ![Canadjun](https://avatars.discourse-cdn.com/v4/letter/c/76d3ee/32.png) [@Canadjun](https://boards.straightdope.com/u/Canadjun)\ **Post date:** [February 12, 2010, 8:40pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/24 "2010-02-12T20:40:13Z")
> [@Maryna](#): > > A photo [here](http://en.wikipedia.org/wiki/File:Mandrill_at_Singapore_Zoo.jpg), without the vitals though. I don’t recall testicles as such, my mom must have been convincing. How about [this](http://en.wikipedia.org/wiki/File:Chlorocebus_pygerythrus_Gr%C3%BCne_Meerkatze.JPG)critter? ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [February 12, 2010, 8:44pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/25 "2010-02-12T20:44:31Z")
> [@umop\_ap\_sdn](#): > > I wonder something similar to that, why couldn’t chlorophyll be absorbed from plants and distributed to the skin or hair. IIRC don’t flamingos do something similar with the red pigments from the creatures they eat so unless it has to do with feather structure… Flamingos do get their pink coloration from the carotenoids in their diets (from algae and brine shrimp). If they don’t get them, they are white. Zoo flamingos are sometimes fed supplements to keep them brilliant pink for the visitors. The same supplement is sometimes fed to farmed salmon so that they are a nice pink color when they become filets. I don’t know how cholorophyll is absorbed or broken down once ingested. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [February 12, 2010, 8:49pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/26 "2010-02-12T20:49:48Z")
> [@njtt](#): > > It would be _very_ useful if you were subject to predation by birds, as many small mammals are. Most birds have excellent color vision, better than ours. The mammal would not have to be able to see its own color for it to be useful camouflage. > > Come to that, who are the sloths supposed to be hiding from by being green? THey are too big for birds, surely. Monkeys? Snakes maybe? (I am not sure about color vision in reptiles.) Yes, which is why I said it would be less important for NON-camouflage purposes such as sexual signaling. Green isn’t necessary if reddish brown will do the job. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [February 12, 2010, 9:07pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/27 "2010-02-12T21:07:27Z")
> [@Mosier](#): > > Do things really “evolve” parasites to help them? A parasite which causes 100% fatalities goes extinct along with its host. It’s beneficial to the parasite to evolve a _modus vivendi_ where it can live off its host while letting the host survive in a competitive state. Taken to an extreme, it would not be totally incorrect to say that parasites evolve towards being symbiotes, where having the ‘parasite’ is actually a pro-survival trait because the ‘parasite’ is actually a symbiote that positively contributes to the host’s well-being. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [February 12, 2010, 10:18pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/28 "2010-02-12T22:18:47Z")
Honestly, the value of green for camouflage is highly overestimated. Just look at snakes, which clearly are capable of green colors. And yet, most snakes still tend toward black, brown and gray. This makes a lot of sense for snakes as well as mammals. First, you have the problem of seasons. There are some places with year-round green leaves, but many forests and every grassland are green only part of the year. Even in evergreen forests or rainforests, you have to think about what the animals are in contact with. Those that live in the trees are too heavy to hold onto the green leaves; they get around by holding onto brown trunks and branches. Those that live in the ground also do not spend much time on green plants. Instead, they move around between the plants on ground that is mostly brown leaves and dirt. ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [February 12, 2010, 10:53pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/29 "2010-02-12T22:53:27Z")
> [@Blake](#): > > And that’s the answer in a nutshell. Mammals aren’t green because there is no way for them to be green and still retain hair. So Kermit was correct all along. ---
**Author:** ![Love\_Rhombus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/love_rhombus/32/10694_2.png) [@Love\_Rhombus](https://boards.straightdope.com/u/Love_Rhombus)\ **Post date:** [February 12, 2010, 11:24pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/30 "2010-02-12T23:24:00Z")
A monkey infected with [Sakutia](http://dc.wikia.com/wiki/Sakutia) may be green, but such cases are very rare. 😉 ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [February 13, 2010, 12:09am UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/31 "2010-02-13T00:09:58Z")
> [@Blake](#): > > As colibri notes, mammsls can’t actually produce blue or green pigments, so it’s going to be very difficult for them to be blue or green. Birds get away with it because the structure of feathers readily lends itself to diffraction patterning. the same isn’t true of hair. > > And that’s the answer in a nutshell. Mammals aren’t green because there is no way for them to be green and still retain hair. That is no answer at all. It amounts to saying that mammals have not evolved green hair because they have not evolved green hair. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [February 13, 2010, 12:15am UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/32 "2010-02-13T00:15:15Z")
> [@Love\_Rhombus](#): > > A monkey infected with [Sakutia](http://dc.wikia.com/wiki/Sakutia) may be green, but such cases are very rare. 😉 [Green monkey disease](http://en.wikipedia.org/wiki/Green_monkey_disease), by contrast, has spread beyond the DC Comicverse. ---
**Author:** ![notfrommensa](https://avatars.discourse-cdn.com/v4/letter/n/f14d63/32.png) [@notfrommensa](https://boards.straightdope.com/u/notfrommensa)\ **Post date:** [February 13, 2010, 1:25am UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/33 "2010-02-13T01:25:47Z")
there were the Blue People of Kentucky (Appalachia) that were affected with [Methemoglobinemia](http://en.wikipedia.org/wiki/Methemoglobinemia). I used to work with a guy named Fugate before I learned about the disease. To the best of my knowledge, his complexion was like a pair of well-bleached blue-jeans. ---
**Author:** ![thelurkinghorror](https://avatars.discourse-cdn.com/v4/letter/t/7c8e57/32.png) [@thelurkinghorror](https://boards.straightdope.com/u/thelurkinghorror)\ **Post date:** [February 13, 2010, 1:44am UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/34 "2010-02-13T01:44:39Z")
> [@MrDibble](#): > > Well, there are those people who drink colloidal silver… [Argyria](http://www.sciencepunk.com/v5/gallery/stanjones.jpg). ---
**Author:** ![dragoncat](https://avatars.discourse-cdn.com/v4/letter/d/6a8cbe/32.png) [@dragoncat](https://boards.straightdope.com/u/dragoncat)\ **Post date:** [February 13, 2010, 12:04pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/35 "2010-02-13T12:04:25Z")
Lots of interesting posts here I’m enjoying reading. I should have clarified in my original post I was really thinking about green or blue fur/hair, not skin. Not sure why, it just seems different somehow. I was kind of unconvinced by Cecil’s column that a couple of people linked to, but a lot of the other posts are really helpful – thanks!. I don’t entirely see why we can’t answer “why not” about evolution when we are looking at something that happened to all other kinds of animals. But perhaps it would be more useful to break each of those groups down into smaller groups (orders, families etc) as it’s not as though all birds are blue or all fish are green. ---
**Author:** ![Blake](https://avatars.discourse-cdn.com/v4/letter/b/a9a28c/32.png) [@Blake](https://boards.straightdope.com/u/Blake)\ **Post date:** [February 13, 2010, 3:15pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/36 "2010-02-13T15:15:33Z")
> [@njtt](#): > > That is no answer at all. It amounts to saying that mammals have not evolved green hair because they have not evolved green hair. I think you need to go back and rad my post again. ---
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [February 13, 2010, 9:09pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/37 "2010-02-13T21:09:09Z")
> [@dragoncat](#): > > I don’t entirely see why we can’t answer “why not” about evolution when we are looking at something that happened to all other kinds of animals. But perhaps it would be more useful to break each of those groups down into smaller groups (orders, families etc) as it’s not as though all birds are blue or all fish are green. Because evolution isn’t directed. It’s ultimately based on a random process. The only real answer to “why didn’t this obviously better strategy evolve?” is just that it never arose through the process of random mutation. You can dissect why it might be difficult for it to arise, but ultimately, that’s what it reduces to. ---
**Author:** ![dracoi](https://avatars.discourse-cdn.com/v4/letter/d/90db22/32.png) [@dracoi](https://boards.straightdope.com/u/dracoi)\ **Post date:** [February 13, 2010, 9:45pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/38 "2010-02-13T21:45:03Z")
> [@dragoncat](#): > > I don’t entirely see why we can’t answer “why not” about evolution when we are looking at something that happened to all other kinds of animals. If you believe in natural selection as an essentially random process of reproduction, mutation and survival, then asking “Why not?” is about as useful as a craps player asking “Why haven’t I rolled a 7 yet?” Investigating the situation might show that the dice are loaded, that the player is cheating or that some other factor does explain why not. But most of the time, you can’t do anything better than “Because it just hasn’t happened yet.” ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [February 14, 2010, 2:40pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/39 "2010-02-14T14:40:35Z")
> [@Blake](#): > > I think you need to go back and rad my post again. I did, and it is still tautologous. I think you need to think about what you wrote a bit harder. To say that mammals cannot produce a pigment that will color their hair green is just to say they have not evolved green hair. It is no explanation of why they have not evolved the ability to produce such a pigment (and, consequently, have such hair). If they had evolved green hair, they would have evolved such a pigment. All the stuff about skin and diffraction patterns is irrelevant to this purely logical point. ---
**Author:** ![Polycarp](https://avatars.discourse-cdn.com/v4/letter/p/82dd89/32.png) [@Polycarp](https://boards.straightdope.com/u/Polycarp)\ **Post date:** [February 14, 2010, 4:23pm UTC](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671/40 "2010-02-14T16:23:00Z")
> [@njtt](#): > > I did, and it is still tautologous. I think you need to think about what you wrote a bit harder. To say that mammals cannot produce a pigment that will color their hair green is just to say they have not evolved green hair. It is no explanation of why they have not evolved the ability to produce such a pigment (and, consequently, have such hair). If they had evolved green hair, they would have evolved such a pigment. All the stuff about skin and diffraction patterns is irrelevant to this purely logical point. Evolution works by re-adapting existing organs, tissues, biochemicals, etc. A forelimb can adapt as a leg for quadrupedal walking and running, an arm and hand for arboreal locomotion or manipulation in bipeds, a wing for flight, a flipper for aquatic propulson, etc. The same muscles a child uses to wrinkle up its nose are greatly expanded to produce prehensileness in an elephant’s or tapir’s trunk. The air-filled swim bladder used for buoyancy and balance by primitive fish turns, on the one hand, into the oil-reservoir swim bladder of advanced fish, and into the lungs of lungfish and tetrapods. Carotene has multiple functions in various creatures, depending on their needs (pigmentation, nutrient storage, building block for vitamin synthesis, etc.) What is being said, I believe, is that there is nothing that is or can be adapted to a green or blue pigment in either hair follicles or skin. It’s not just the tautological “there’s no pigment because there’s no pigment” that you are reading it as – no matter how useful grass- or leaf-green coloration might be to a small plains- or tree-living herbivore, there is nothing that can be easily adapted to provide the proper coloration. Most pigments have other purposes – oxygen transport for hemoglobin, the uses noted above for carotene, photosynthesis for chlorophyll, etc. – and their use for coloration becomes important only as an advantage when they are present for their other physiological purpose. So, yeah, it’s true that “there’s no green or blue pigment present because there’s no green or blue pigment present” – but the point is that there’s no other physiological reason for them to be present, so that they can be adapted for protecvtive coloration. Carotene is useful for food storage – so orange/red/brown coloration can be easily done by concentrating the carotene present. There’s no substance which could function/be adapted as a green or blue pigment similarly present. [Previous page](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671.md?page=1) [Next page](https://boards.straightdope.com/t/why-no-green-mammals-or-blue/528671.md?page=3)