1y ago

Ever notice mammals never seem to come in green?

Birds, fish, reptiles, amphibians, insects? Sure. But no mammals.

So I had to google it. Apparently, there is a sloth that moves around so slowly moss grows all over it and it doesn't care. So it may appear green, but only in the sense that it wears it.

61 comments

Good article here https://nature-notes.riverlegacy.org/how-come-there-are-no-blue-or-green-mammals
- So I skimmed that and it seems the tldr is mammals have melanin (and I'm guessing the other animals don't)
- Very nice read, thanks
- Great read! That explains a lot.
  I've been deep diving a bit myself and found this article that explains another thing that's puzzled me over the years. Some birds have crazy vibrant coloration that almost glistens, like peacock feathers. Outside of the zoo, I've noticed it a bit in common grackles. They look black on first glance, but when you study them closely, they have this kind of purple sheen around their heads. Apparently, it's still melanin at work here, but it's structured in a very special way.

This may have already been covered but whilst there might not be mammals that appear green to human eyes there are certainly mamals that appear green to the prey/predators in their environment.
Perfect example is a tiger who (to us) stands out like a sore thumb with its orange fur but is perceived as green with black stripes through the eyes of its prey, making it very well camouflaged in the jungle.
- Do you mean my cats are actually green in the eyes of it's potential prey?
  
  walking 🥑

You’d think evolutionary, there would be at least some green mammals to help them blend into the plant life around them. Like bunnies hiding in bushes, or monkeys in trees. I suppose shades of brown work similarly in the same situations.
I know some predators don’t see color the same way humans do — could the lack of green and dominance of brown have something to do with seeing motion, or heat, or something else we don’t see?
- iirc, the reason tigers are black and orange stripey is because deers and whatever else they eat don't see orange, they see green. This blends the tiger in with the surroundings better.
  
  That's why hunters' jackets are bright orange. Hides them from game (whilst simultaneously making them visible to other people)
- Right? I guess that's what puzzles me the most about it. It must be really hard for mammals to become green since you would think it would confer an advantage in many environments you find them in.
  I guess there are a lot of mammal species that kind of make themselves scarce during the broad daylight hours, so maybe green camouflage is less relevant if you're only out between dusk and dawn?
- This is just a guess, but could it be that brown is more useful since mammals (at least the first ones) dwell on and in the ground, where brown would be more beneficial for survival?
- At least humans have the highest sensitivity specifically around 555 nm (green).

Does it count if they are glowing bunnies?
- Ha!! You really had to go down the "rabbit hole" for that one I bet! Awesome.
- "yes uhh... We need to make bunnies that glow in the dark... for medicine.... Yess."

They're out there but it's been hard to document their existence since they blend in so well with their environment. This natural camouflage is a double-edged sword, however: they may be able to avoid getting eaten by predators but it also makes reproduction particularly challenging since they have a hard time finding one another to do it like the Discovery channel.
Even when a potential breeding pair are able to meet up, their coupling is far from guaranteed due to the abundance of other green orifices in their usual habitats. Grass-covered mole tunnels, mossy logs with holes in them and bee nests in leafy trees have all been accidental natural fleshlights for these poor creatures. Like they say, it's not easy being green.

We might not be looking at them with the right eyes
https://www.theguardian.com/science/2023/oct/04/positively-glowing-fluorescent-mammals-are-far-more-common-than-earlier-thought-study-suggests
- Wow, that is fascinating!
  Makes me wonder about the other direction, going into the near infrared as opposed to UV. I remember from a class in remote sensing that many plants are actually most reflective in that band (more so than in green, even). NIR air photos are often used by biologists to get an indication of the health of a forest. But I have no idea whether animals also reflect NIR? It may be that most animals cannot see in that band in the first place, so it would not offer any camouflage advantage.

What about Shrek
- He's an onion

I don't know how relevant this is but I heard human eyes are very good at picking shades of green out. Maybe mammals are generally good at spotting greens and so hiding as a green thing doesn't work as well. Just a guess though
- From what other posters are saying, it may be the other way around? That is, most mammals cannot see green, so it doesn't matter from a camouflage perspective among mammals. Humans (and primates in general) are an outlier in this repect.
  Bird of prey can, though, so there's that.
  
  Word! That's cool
- I thought veritasium explained in his night vision video that this wasn't the case? I'm not sure though.
  
  I thought Veritasium was a Harry Potter spell but apparently I should have already known and watched a YouTube video before posting my silly thoughts.

This is an interesting question but I don't think it is restricted to green. Isn't the same true of purple, blue and red? I'm not talking about just reddish like human hair or a red panda but truly bright red like a cardinal. I would imagine it has something to do with our evolutionary history. Complete speculation here but laced with a few facts I picked up. I hear the common ancestor of mammals emerged around the time the dinosaurs became extinct and was basically a tiny rodent like a shrew. I wonder if as a small animal that can't fly or swim it had to hide a lot and basically just came in shades of brown. So maybe any genes for other colors were lost before that common mammalian ancestor emerged and although mammals have lots of patterns they don't have many colors.
- Baboons have some bright reds and blues, but they are certainly the exception that proves the rule on mammal colors.
- Blue? Hello blue whales & dolphins? :)

Best I've got is sloths. And they're only green because algae grows on them. And I know it sounds like cheating because they aren't intrinsically green but before you completely discount it there are animals that wouldn't be the color they are in a different environment. For instance, flamingos are only pink because of the seafood they eat. If fed a different diet they can be almost white.
- Yeah fair. I had painted glass fish in my aquarium at one point and discovered the "paint" came from feeding them dyed food and eventually faded away when I gave them normal food back at home. They are naturally transparent for the most part which, frankly, I thought was cooler. I did have a gourami that was legit green though, as far as I could tell.

What about the Hulk???
- Not a mammal, he hatched from a green egg
  The ones from Dr Seuss
  
  Wouldn't that make him a monotreme?

I think you're right. I can't think of a single green mammal. Why can we have green or blue eyes, but not other things?

Orions are demonstrably mammals, but unfortunately fictional.
- You can't prove that. Orions are real, do not slander the Word of the great prophet Roddenberry, Peace Be Upon Him.

Algae-covered sloths are about as close as you get.

I remember reading an article in a Nickelodeon magazine when I was a kid about a cat that had a genetic defect that gave it green fur. It looked pretty cool.
- Crazy. I had to look it up and I found some stuff, including this old web article from 2002 that talks about this cat. The cat's name was, Miss Greeny, apparently.
  There are multiple sources, but there is no wiki page and none of the sources seem well known, so I'm having a hard time figuring out if it's legit, or just a really good hoax.