no green mammals?

sb said:

How come mammals that live in green forests aren't green
(for camouflage) ?

Because they don't hide next to leaves? Most forest mammals
probably sit next to trunks or scrabble around in/on the
soil. Hence, being trunk/soil coloured makes more sense for
camouflage. Others only come out at night, which is not
terribly green either.

Other mammals probably don't bother with camouflage - they
have different protective mechanisms (like running away
very quickly).

Bob

--
Bob O'Hara Department of Mathematics and Statistics
P.O. Box 4 (Yliopistonkatu 5) FIN-00014 University of
Helsinki Finland Telephone: +358-9-191 23743 Mobile:
+358 50 599 0540 Fax: +358-9-191 22 779 WWW:
rni.helsinki.fi~bohOpen ↗ Journal of Negative
Results - EEB: www.jnr-eeb.org

On Mon, 5 Apr 2004 05:22:08 +0000 (UTC), [email hidden] (sb)

Quoted message said:

How come mammals that live in green forests aren't green
(for camouflage) ?

This is one more example of how "intelligent design"
has failed. Mammals simply don't know how to make a
green pigment.

I believe that green color in animals is usually a
structural color caused by light interference in a regular
crystalline array, rather than a pigment color caused by
light absorbing compound. Chromatophore cells in fish and
amphibian and reptilian skin and feathers can all produce
structural colors, but mammals can't do this in hair.

Melanin is, of course, the most important mammalian
pigment and it just doesn't get green. Other pigments are
derived from carotenoid chemicals we get by eating
plants. Unfortunately, the green chlorophyll we also get
by eating plants breaks apart during digestion and loses
its green color.

You also have to consider that green forests are really
largely brown where mammals are found -- along the branches
and trunks of the trees or at ground level. Even the birds
that nest and feed in the leaf canopy are seldom green.

[email hidden] (sb) wrote in message news:<[email hidden]>...

Quoted message said:

How come mammals that live in green forests aren't green
(for camouflage) ?

One exception is the three toed sloth. Here is a (not very
mature) reference: kalama.doe.hawaii.edupt00Open ↗
6/G4/C3/jeremyp.html

As I am a strong believer in the heuristic value of "the
exception that proves the rule", this suggests that mammals
don't typically use this kind of protective coloration
because they don't need to - elaborate nervous systems and
great warm-blooded speed are a better defense. (The sloth is
proverbially slow.) It might be interesting to compare
mammals and birds to their cold-blooded competitors.

sb said:

How come mammals that live in green forests aren't green
(for camouflage) ?

I have often wondered my mammals are deficient in coloration
when compared to birds, insects, fish & reptiles. Mammals
cannot make green, nor true blue, nor true red, but only
shades of brown, black & white. Why is that?

The fitness boost that many animals gain from coloration
ought to do the same for at least some mammals, no?

m

--
"Many are stubborn in pursuit of the path they have chosen,
few in pursuit of the goal." - Friedrich Nietzsche

annevolve.sourceforge.netannevolve.sourceforge.netOpen ↗ is what I'm into
nowadays. Humans may write to me at this address: zenguy
at shaw dot ca

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

[email hidden] (sb) wrote:

Quoted message said:

Quoted message said:

How come mammals that live in green forests aren't green
(for camouflage) ?

This is one more example of how "intelligent design" has
failed. Mammals simply don't know how to make a green
pigment.

Well - there's "green hair syndrome".

Also check out the "Three-toed sloth":

``Why do three-toed sloths have green hair? The three-toed
sloth, one of the slowest creatures on earth, has specially
adapted hair which encourages algae growth. The algae gives
it a greenish appearance.''

- gocornerstore.comAugustOpen ↗
_F/2F.html

...and - of course - there's the "green beard effect" ;-)
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

[email hidden] wrote or quoted:

Quoted message said:

I have often wondered my mammals are deficient in
coloration when compared to birds, insects, fish &
reptiles. Mammals cannot make green, nor true blue, nor
true red, but only shades of brown, black & white. Why
is that?

Because it is not true?

pims.math.camandrill.jpgOpen ↗
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

Tim Tyler said:

[email hidden] wrote or quoted:

Quoted message said:

I have often wondered my mammals are deficient in
coloration when compared to birds, insects, fish &
reptiles. Mammals cannot make green, nor true blue, nor
true red, but only shades of brown, black & white. Why
is that?

Because it is not true?

You are right; it is merely rare. I looked this up with
google and found this:

" mandrill: the predominantly brown coloring is due to
melanin, but the red and blue markings are also caused by
melanin, in the latter case by the refraction of light due
to specific spatial arrangements of the pigment granules in
the skin areas involved. "

This means that some baboon species have evolved a physical
property similar to that found in the animals that I
mentioned above, where the wave properties of light are used
to produce coloration. I wonder if any other genus of
mammals exhibit this property?

Of course some mammals have yellow or orange or coppery fur;
humans included. I was thinking of that as a shade of brown,
but perhaps shades of yellow need to be included in can be
seen in fur.

m

--
"Many are stubborn in pursuit of the path they have chosen,
few in pursuit of the goal." - Friedrich Nietzsche

annevolve.sourceforge.netannevolve.sourceforge.netOpen ↗ is what I'm into
nowadays. Humans may write to me at this address: zenguy
at shaw dot ca

[email hidden] wrote in message news:<[email hidden]>...

Quoted message said:

sb said:

How come mammals that live in green forests aren't green
(for camouflage) ?

I have often wondered my mammals are deficient in
coloration when compared to birds, insects, fish &
reptiles. Mammals cannot make green, nor true blue, nor
true red, but only shades of brown, black & white. Why
is that?

The fitness boost that many animals gain from coloration
ought to do the same for at least some mammals, no?

m

Bright colors often seen in birds/reptiles, amphibians, fish
etc are often for display purposes. The color is used to
communicate as opposed to conceal.

Since most mammals can't see colors anyway, there would be
no point in having bright colors.

However, primates can see color and there are many examples
of brightly colored primates.

Keith

On Tue, 6 Apr 2004 16:09:22 +0000 (UTC), Tim Tyler <[email hidden]>

Quoted message said:

[email hidden] wrote or quoted:

Quoted message said:

I have often wondered my mammals are deficient in
coloration when compared to birds, insects, fish &
reptiles. Mammals cannot make green, nor true blue, nor
true red, but only shades of brown, black & white. Why
is that?

Because it is not true?

pims.math.camandrill.jpgOpen ↗

The statement really applies to hair colors. Many
organisms can produce structural colors including green
and blue in cutaneous cells. The picture shows skin color,
not hair color.

"Tim Tyler" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

[email hidden] (sb) wrote:

Quoted message said:

Quoted message said:

How come mammals that live in green forests aren't

green (for camouflage) ?

Quoted message said:

Quoted message said:

This is one more example of how "intelligent design" has

failed.

Quoted message said:

Quoted message said:

Mammals simply don't know how to make a green pigment.

Well - there's "green hair syndrome".

Also check out the "Three-toed sloth":

``Why do three-toed sloths have green hair? The three-toed

sloth, one of

Quoted message said:

the slowest creatures on earth, has specially adapted

hair which

Quoted message said:

encourages algae growth. The algae gives it a greenish

appearance.''

Quoted message said:

-

gocornerstore.com2F.htOpen ↗
ml

Quoted message said:

...and - of course - there's the "green beard effect" ;-)
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove

lock to reply.

Hmm...quoting from that reference: "Scientists think sloths
may get nutrition from the algae when they groom
themselves." Can someone in genetic engineering work on this
for [censored] sap? I can save a lot of money on salad! ....tonyC

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Tim Tyler said:

[email hidden] wrote or quoted:

Quoted message said:

Quoted message said:

Quoted message said:

I have often wondered my mammals are deficient in
coloration when compared to birds, insects, fish &
reptiles. Mammals cannot make green, nor true blue, nor
true red, but only shades of brown, black & white. Why
is that?

Because it is not true?

pims.math.camandrOpen ↗
ill.jpg

The statement really applies to hair colors. Many
organisms can produce structural colors including green
and blue in cutaneous cells. The picture shows skin color,
not hair color.

Perhaps try these links, then:

Blue:
* Mandrill: geometer.orgmandrill.jpgOpen ↗
mindysmem.orgmandril1.jpgOpen ↗
kevinschafer.comeslgv7.jpgOpen ↗

* Blue monkey: spinner.scis.nova.edusumitrOpen ↗
a/safari2001/baboon/bluemonkey.jpg

Red (OK - maybe not "true" red ;->😉:
* Red squirrel dnr.state.oh.usimageOpen ↗
s/redsquirrelx.jpg

* Red Fox
johnwasserman.coml3revised.jpgOpen ↗

* Tori Amos ;-) tori-tori-Open ↗
fanpage.de/Biographie/tori_red_hair.jpg
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

On Wed, 7 Apr 2004 16:38:52 +0000 (UTC), Tim Tyler <[email hidden]>

Quoted message said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Tim Tyler said:

[email hidden] wrote or quoted:

Quoted message said:

Quoted message said:

> I have often wondered my mammals are deficient in
> coloration when compared to birds, insects, fish &
> reptiles. Mammals cannot make green, nor true blue,
> nor true red, but only shades of brown, black & white.
> Why is that?

Because it is not true?

pims.math.camandriOpen ↗
ll.jpg

The statement really applies to hair colors. Many
organisms can produce structural colors including green
and blue in cutaneous cells. The picture shows skin
color, not hair color.

Perhaps try these links, then:

Blue:
* Mandrill: geometer.orgmandrill.jpgOpen ↗
mindysmem.orgmandril1.jpgOpen ↗
kevinschafer.comeslgv7.jpgOpen ↗

* Blue monkey: spinner.scis.nova.edusumitOpen ↗
ra/safari2001/baboon/bluemonkey.jpg

Red (OK - maybe not "true" red ;->😉:
* Red squirrel dnr.state.oh.usimagOpen ↗
es/redsquirrelx.jpg

* Red Fox
johnwasserman.coml3revised.jpgOpen ↗

* Tori Amos ;-) tori-tori-Open ↗
fanpage.de/Biographie/tori_red_hair.jpg

Sorry, I don't see a clear real blue pigment (or
interference color) in the fur. Some pictures might
possibly have white hairs that show a bluish tinge. Only
one shows real blue and, not knowing enough about
mandrills, might still be skin coloration. Is there a
citation to a chemical pigment that is blue or to a
specific semi-crystalline array of reflective molecules
that produce a structure blue color in hair?

I never had a problem with red pigments in hair. Those are
quite common.

[email hidden] (sb) wrote in message news:<[email hidden]>...

Quoted message said:

How come mammals that live in green forests aren't green
(for camouflage) ?

Here's my own take on this:

1. The hypothesis that mammals simply did not manage to find
a recipe for green pigmentation is not a plausible one:
some mammals have green eyes, birds and reptiles are
often green, and reptiles are earlier on the evolutionary
tree than mammals. Pigmentation just does not strike me
as something difficult to find a genetic recipe for (And
by the way, polar bears turn green in worm zoos because
of parasites - if they "wanted" to be green, they could
at least use this kind of symbiosis)

2. The hypothesis that mammals are better camouflaged when
they are not gren is interesting, but probably wrong.
Snipers wear greenish camouflage when hiding on trees.
The argument could apply to certain mammals, but not most
of them. Just look at any "monkey on a tree" or "monkey
in the bushes" picture, and imagine the monkey green.

3. The hypothesis that the predators and prey do not see
colors, so pigmentation does not matter is also
intersting. I would have expected both preditors
hunting for poorly camouflaged prey and prey looking
out for poorly camouflaged predators to develop color
vision. It's more believable that color _vision_ is
difficult to develop (Perhaps it requires serious
changes in the brain)

(BTW, wasn't there an article in the news lately about how
there is an evolutionary trend to either develop color
vision or to lose it - don't remember which)

Anthony Cerrato <[email hidden]> wrote in message news:<[email hidden]>...

Quoted message said:

"Tim Tyler" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

[email hidden] (sb) wrote:

Quoted message said:

Quoted message said:

>How come mammals that live in green forests aren't

green (for camouflage) ?

Quoted message said:

Quoted message said:

This is one more example of how "intelligent
design" has

failed.

Quoted message said:

Quoted message said:

Mammals simply don't know how to make a green pigment.

Well - there's "green hair syndrome".

Also check out the "Three-toed sloth":

``Why do three-toed sloths have green hair? The
three-toed

sloth, one of

Quoted message said:

the slowest creatures on earth, has specially adapted

hair which

Quoted message said:

encourages algae growth. The algae gives it a greenish

appearance.''

Quoted message said:

-

gocornerstore.comgocornerstore.comOpen ↗
2F.html

Quoted message said:

...and - of course - there's the "green beard
effect" ;-)
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove

lock to reply.

Hmm...quoting from that reference: "Scientists think
sloths may get nutrition from the algae when they groom
themselves." Can someone in genetic engineering work on
this for [censored] sap? I can save a lot of money on salad!
....tonyC

It's funny you should mention this. We need volunteers for a
study, to mate with the green sloth.

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Tim Tyler said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

On Tue, 6 Apr 2004 16:09:22 +0000 (UTC), Tim Tyler
<[email hidden]> wrote:
>[email hidden] wrote or quoted:

Quoted message said:

>> I have often wondered my mammals are deficient in
>> coloration when compared to birds, insects, fish &
>> reptiles. Mammals cannot make green, nor true blue,
>> nor true red, but only shades of brown, black &
>> white. Why is that?
>
>Because it is not true?
>
>pims.math.camandrilOpen ↗
>l.jpg

The statement really applies to hair colors. Many
organisms can produce structural colors including green
and blue in cutaneous cells. The picture shows skin
color, not hair color.

Perhaps try these links, then:

Blue:
* Mandrill:
geometer.orgmandrill.jpgOpen ↗
mindysmem.orgmandril1.jpgOpen ↗
kevinschafer.comeslgv7.jpgOpen ↗

* Blue monkey: spinner.scis.nova.edusumOpen ↗
itra/safari2001/baboon/bluemonkey.jpg

[...]

Quoted message said:

Sorry, I don't see a clear real blue pigment (or
interference color) in the fur. Some pictures might
possibly have white hairs that show a bluish tinge. Only
one shows real blue and, not knowing enough about
mandrills, might still be skin coloration. Is there a
citation to a chemical pigment that is blue or to a
specific semi-crystalline array of reflective molecules
that produce a structure blue color in hair?

The most-clearly-blue image so far.

A mandril mane:

das-tierlexikon.demandrill bild.htmOpen ↗

*Surely* this one can leave no possible shadow of a doubt
that the hair really does contain a blue pigment.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

On Thu, 8 Apr 2004 16:11:49 +0000 (UTC), [email hidden] (sb)

Quoted message said:

[email hidden] (sb) wrote in message
news:<[email hidden]>...

Quoted message said:

How come mammals that live in green forests aren't green
(for camouflage) ?

Here's my own take on this:

1. The hypothesis that mammals simply did not manage to
find a recipe for green pigmentation is not a plausible
one: some mammals have green eyes, birds and reptiles
are often green, and reptiles are earlier on the
evolutionary tree than mammals. Pigmentation just does
not strike me as something difficult to find a genetic
recipe for (And by the way, polar bears turn green in
worm zoos because of parasites - if they "wanted" to be
green, they could at least use this kind of symbiosis)

<snip two other observations>

There is a difference between pigment color and structural
color. Green and blue in animals is almost always a
structural color, produced by either interference or
scattering of light, not by a pigment that absorbs light.
Also, there is a difference between color of hair and color
of skin. Mammals can produce structural colors in their
skin. Reptiles, amphibians, fish, and many invertebrates
produce both pigment and structural colors in cutaneous
chromatophore cells. Mammalian hair seems to use only
melanin as a pigment and seems unable to produce structural
colors of any intensity. (White hairs do sometimes take on
slight hues).

See my literature citation to primate colors in another post
in this thread.

On Thu, 8 Apr 2004 16:11:50 +0000 (UTC), Tim Tyler <[email hidden]>

Quoted message said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Tim Tyler said:

r norman <rsn_@_comcast.net> wrote or quoted:
> On Tue, 6 Apr 2004 16:09:22 +0000 (UTC), Tim Tyler
> <[email hidden]> wrote:
> >[email hidden] wrote or quoted:

> >> I have often wondered my mammals are deficient in
> >> coloration when compared to birds, insects, fish &
> >> reptiles. Mammals cannot make green, nor true blue,
> >> nor true red, but only shades of brown, black &
> >> white. Why is that?
> >
> >Because it is not true?
> >
> >pims.math.camandriOpen ↗
> >ll.jpg
>
> The statement really applies to hair colors. Many
> organisms can produce structural colors including
> green and blue in cutaneous cells. The picture shows
> skin color, not hair color.

Perhaps try these links, then:

Blue:
* Mandrill:
geometer.orgmandrill.jpgOpen ↗
mindysmem.orgmandril1.jpgOpen ↗
kevinschafer.comeslgv7.jpgOpen ↗

* Blue monkey: spinner.scis.nova.edusuOpen ↗
mitra/safari2001/baboon/bluemonkey.jpg

[...]

Quoted message said:

Sorry, I don't see a clear real blue pigment (or
interference color) in the fur. Some pictures might
possibly have white hairs that show a bluish tinge. Only
one shows real blue and, not knowing enough about
mandrills, might still be skin coloration. Is there a
citation to a chemical pigment that is blue or to a
specific semi-crystalline array of reflective molecules
that produce a structure blue color in hair?

The most-clearly-blue image so far.

A mandril mane:

das-tierlexikon.demandrill bild.htmOpen ↗

*Surely* this one can leave no possible shadow of a doubt
that the hair really does contain a blue pigment.

The shadow of doubt is an enormous black hole. The nose
clearly has bright blue skin color, but the fur is not
at all blue.

Check any web site dealing with mandrills. None that I could
find that described color patterns in some detail and depth
even hinted at blue or even bluish color in the fur. Gray
and olive-brown OK, blue NO.

And then you might want to look at the scientific
literature:
P. Sumner and J.D. Mollon Colors of Primate Pelage and
Skin: Objective Assessment of Conspicuousness American
Journal of Primatology 59:67-91 (2003) vision.p-vision.p-Open ↗
sychol.cam.ac.uk/jdmollon/papers/sumner_mollon2003.pdf

Their Figure 4 clearly shows a variety of fur colors
(chromaticities, actually) with absolutely none in the blue
range. Skin color was distinctly different. Yes, mandrills
were included in their sample of 31 species of primates. The
caption to Fig. 4 states: "The primate fur has a restricted
range of chromaticities that lie in a white-yellow/orange
color direction. Lying on roughly the same chromaticity
axis, close on the opposite side of white, is the blue skin
displayed by some catarrhines."

Here is the opening of their discussion section:

"Gamut of Chromaticities Presented by Primate Pelage"

"The range of fur chromaticities displayed by primates is
restricted because mammalian coloration is determined
chiefly by melanin pigments. Different combinations of
pheomelanin and eumelanin (or their absence) can supply a
small range of colors from reddish-brown or orangish-yellow
to white, gray, or black. In nature, orange coloration is
often produced by carotenoids [Nassau, 1983], but these
pigments do not appear to be used in mammalian fur. It has
been reported that there are no detectable concentrations of
carotenoids even in the very orange fur of lion tamarins and
orangutans [Slifka et al., 1999]. In addition, the good
agreement between the measurements of pelts and live animals
indicates that pelage chromaticities do not change much with
the environment or the diet of captive animals. However, it
is undeniable that direct sunlight does cause some bleaching
of fur color, which moves the fur’s chromaticity toward
white, and raises its luminance."

"As Fig. 5 shows, chromaticities of catarrhine skin can
deviate from this restricted distribution of fur. The blue
coloration displayed by species such as Mandrillus sphinx
and Cercopithecus aethiops is caused by Rayleigh scattering
[Nassau, 1983], whereby small particles scatter short-
wavelength (blue) light more strongly than longer-wavelength
(red) light. "

In other words: no blue pigment. Structural blue in skin
only, not in hair.

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

There is a difference between pigment color and structural
color. Green and blue in animals is almost always a
structural color, produced by either interference or
scattering of light, not by a pigment that absorbs light.

Note that this is not the definition of "pigment" given in
the dictionary.

I wonder if this is why it is being claimed that my mandrill
["]http://www.das-tierlexikon.de/mandrill_bild.htm] lacks blue
pigmentation.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Tim Tyler said:

r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

On Wed, 7 Apr 2004 16:38:52 +0000 (UTC), Tim Tyler
<[email hidden]> wrote:
>r norman <rsn_@_comcast.net> wrote or quoted:

Quoted message said:

Quoted message said:

Quoted message said:

>> The statement really applies to hair colors. Many
>> organisms can produce structural colors including
>> green and blue in cutaneous cells. The picture shows
>> skin color, not hair color.
>

Quoted message said:

Quoted message said:

Quoted message said:

>Perhaps try these links, then:
>
>Blue:
> * Mandrill:
> geometer.orgmandrill.jpgOpen ↗
> mindysmem.orgmandril1.jpgOpen ↗
> kevinschafer.comeslgv7.jpgOpen ↗
>
> * Blue monkey: spinner.scis.nova.eduspinner.scis.nova.eduOpen ↗
> sumitra/safari2001/baboon/bluemonkey.jpg

[...]

Quoted message said:

Sorry, I don't see a clear real blue pigment (or
interference color) in the fur. Some pictures might
possibly have white hairs that show a bluish tinge.
Only one shows real blue and, not knowing enough about
mandrills, might still be skin coloration. Is there a
citation to a chemical pigment that is blue or to a
specific semi-crystalline array of reflective molecules
that produce a structure blue color in hair?

The most-clearly-blue image so far.

A mandril mane:

das-tierlexikon.demandrill bild.htmOpen ↗

*Surely* this one can leave no possible shadow of a doubt
that the hair really does contain a blue pigment.

The shadow of doubt is an enormous black hole. The nose
clearly has bright blue skin color, but the fur is not at
all blue.

Did you *actually* visit the site?

My paint program reports the hair of the mandril's mane as:

R:56 G:69 B:103

Pretty damn blue - IMHO.

Quoted message said:

Check any web site dealing with mandrills. None that I
could find that described color patterns in some detail
and depth even hinted at blue or even bluish color in the
fur. Gray and olive-brown OK, blue NO.

And then you might want to look at the scientific
literature:
P. Sumner and J.D. Mollon Colors of Primate Pelage and
Skin: Objective Assessment of Conspicuousness
American Journal of Primatology 59:67-91 (2003) http-
://vision.psychol.cam.ac.uk/jdmollon/papers/sumner_m-
ollon2003.pdf

Their Figure 4 clearly shows a variety of fur colors
(chromaticities, actually) with absolutely none in the
blue range.

If table 1 is anything to go by, one data point represents
a mandrill.

Perhaps they failed to sample from a blue area.
Consequently, figure 4 says little or nothing about the
colour of some mandrills mane or rump hair.

Quoted message said:

Skin color was distinctly different. Yes, mandrills were
included in their sample of 31 species of primates. The
caption to Fig. 4 states: "The primate fur has a
restricted range of chromaticities that lie in a white-
yellow/orange color direction. Lying on roughly the same
chromaticity axis, close on the opposite side of white, is
the blue skin displayed by some catarrhines."

Here is the opening of their discussion section:

"Gamut of Chromaticities Presented by Primate Pelage"

"The range of fur chromaticities displayed by primates is
restricted because mammalian coloration is determined
chiefly by melanin pigments. Different combinations of
pheomelanin and eumelanin (or their absence) can supply a
small range of colors from reddish-brown or orangish-
yellow to white, gray, or black. In nature, orange
coloration is often produced by carotenoids [Nassau,
1983], but these pigments do not appear to be used in
mammalian fur. It has been reported that there are no
detectable concentrations of carotenoids even in the very
orange fur of lion tamarins and orangutans [Slifka et al.,
1999]. In addition, the good agreement between the
measurements of pelts and live animals indicates that
pelage chromaticities do not change much with the
environment or the diet of captive animals. However, it is
undeniable that direct sunlight does cause some bleaching
of fur color, which moves the fur?s chromaticity toward
white, and raises its luminance."

"As Fig. 5 shows, chromaticities of catarrhine skin can
deviate from this restricted distribution of fur. The blue
coloration displayed by species such as Mandrillus sphinx
and Cercopithecus aethiops is caused by Rayleigh
scattering [Nassau, 1983], whereby small particles scatter
short-wavelength (blue) light more strongly than longer-
wavelength (red) light. "

In other words: no blue pigment. Structural blue in skin
only, not in hair.

It also apparently claims that the blue colour is an
artefact of small particles scattering blue light - while
red and green light is absorbed.

``As Fig. 5 shows, chromaticities of catarrhine skin can
deviate from this restricted distribution of fur. The blue
coloration displayed by species such as Mandrillus sphinx
and Cercopithecus aethiops is caused by Rayleigh scattering
[Nassau, 1983], whereby small particles scatter short-
wavelength (blue) light more strongly than longer-wavelength
(red) light. The blue caused by Rayleigh scattering is often
called ??Tyndall blue?? (blue sky is an example). Thus the
range of blues in the mandrill and vervet have very similar
chromaticities to the blues of the sky. In these primates,
the incident light of shorter wavelengths is scattered
toward the observer by small particles in the skin, whereas
the longer wavelengths pass through and are absorbed by an
underlying dark layer of melanin. The larger the scattering
particles, the less saturated the blue color will be,
because more middle wavelengths will also be scattered.''

They distinguish (12 lines down from the quoted section
above) between blue casued by scattering, and blue caused by
pigmentation.

My understanding is that the *definition* of pigment is that
it is a substance that produces a colour when illuminated.

AFAIK, it doesn't matter whether the colour is produced by
reflecting light, absorbing and partially re-radiating it,
or transmitting some components and scattering other ones -
*all* that matters is that a colour is produced.

Consequently, I don't know about their notion that the
mandrill's nose contains no blue pigment either - but I
*do* know is that both the nose and the mane of the
mandrill in the photo are plainly blue - as any child would
be able to see.
--
__________
|im |yler timtyler.orgtimtyler.orgOpen ↗ [email hidden] Remove
lock to reply.