*Infodumps at you*

[malymin]

So mammals get their coloration from melanin. There's two main types of melanin: eumelanin and phaeomelanin. Eumelanin is black, and in lower densities produces greys, browns, and ashy blonde. Phaeomelanin is rusty red-brown, and in lower densities produces rust-orange, cream, and yellow blonde. Pretty much every hair and skin color found in humans and non-human mammals alike comes from these two pigments! Fun fact: lips (as well as the nips and the genitals) are densely pigmented with phaeomelanin in humans.

Some birds (such as ducks, chickens, and pigeons) get most or all of their adult plumage color from melanins, too. The yellow of ducklings and chicks comes from carotenoids, though, as does the bright yellow and orange hues often found on duck and chicken beaks and feet.

All reptiles produce eumelanin, but information on whether any of the major non-avian clades produce phaeomelanin is a bit spotty. Red-browns, gold-browns, etc in snakes often come from a mix of eumelanin and carotenoids.

Birds are able to produce "structural" colors by altering how light hits or passes through their pigmented feathers. Reptiles are able to do the same with structures in their scales or skin. (Birds can also produce structural color in the skin, btw - this is how cassowaries have blue faces.) This is how a male mallard has a green head and blue wing feathers, despite not producing green or blue pigment; this is also how green iguanas, blue-tailed skinks, etc produce their colors. Mammal hair lacks the complex structures of bird feathers, so mammals can't create complex structural color in their soft integument the way birds do. Mammals can produce structural colors in their skin - this is how mandrills develop their blue faces and butts. (Also, vervet monkeys have literal blue balls. For some reason, mammal structural colors are often limited to genitals...? Golden snub-nose monkeys have blue faces, though, which is quite gorgeous against their phaeomelanin-rich golden fur.)

Eyes are the main place you'll see structural color in most mammals. Any instance of blue eyes is structural color, as is green - green eyes are the result of yellow pigment layered over blue structural color.

I hope you learned something new today! ^_^

Comments

[stepnix]

👏 👏 👏

[oddprophet]

I do enjoy Biology Fun Fact Power Hour

[malymin]

^u^ I'm glad!

[kalium]

re structural colour in mammal hair - golden moles! Though I admit it's not as flashy, but cool that it exists.

[malymin]

Oh yea, those little weirdos!

Only didn't mention them because they kind of have more of an iridescent sheen on their pigment-based colors than, like, creating the impression of a solidly blue, green, purple, etc animal.