Fluorescent squirrel fur

[IronWing]

Flying squirrels have pink fluorescing fur!

https://www.iflscience.com/plants-a...ve-glowinthedark-hot-pink-fur-under-uv-light/

The finding is cool but then the reporter goes on to speculate on why this might be and completely misses the point that squirrels don't have UV lights to show off their cool pink fur. I propose we remedy this.

Edit: I edited the title to be less obnoxious.

 

[clamum]

The article wondering why they have that flourescent effect under UV light posits that it might be due to camo, an anti-predator effect to confuse would-be predators, or a matter of sexual/mate selection. Reasonable guesses I think, as long as its predators (and other flying sequirrels in the case of sexual/mate selection) can see in UV light. Otherwise it don't make sense.

 

[Charmonium]

Or it could just be a random mutation in search of a survival advantage - which is one theory of how evolution really works.

Also there can be correlations between traits. So whatever biochemistry is creating a fluorescing pigment in their fur might be a side effect of some other biological process that actually does bestow a survival advantage.

 

[Paperdoc]

No, they don't have UV lights. But ALL sunlight contains substantial UV light, some of which penetrates our atmosphere and reaches us (hence sunburn.) Thus, at any time of the day IF that squirrel is out and about, that component of their fur colour would be apparent to any animal that has the right eyesight colour range. There are two possible ways for this to work. One is the way we see things - that is, seeing the pink colour generated by fluorescence. Although apparently that colour is not noticed easily by humans among the other colours of the fur, other eye types might see it more clearly.

But the second part is likely important, and that's the mechanism by which we (and other animals) see colour. We normally do not see colour made by something (unless it is a light emitter). We see the portions of the original light source (sunlight e.g.) that are NOT absorbed by the components of the object (in this case, fur) and are reflected back to our eyes. We see what are called subtractive colours - the colours produced after the object "subtracts" things from the original light. Now, the reason that the pink colour shows up is that first some component of the fur absorbs UV light (just as a blue object absorbs red and yellow light), and then it re-emits light of a different (pink) colour. That is how fluorescence works, and it's different from simple subtrative colours. So any eye that is able to "see" UV light (unlike human eyes) will see that squirrel's fur MINUS the UV light, and that will appear to that viewer as a different colour from what is "normal" for other fur types. It would be similar to how we humans see some animal fur as dark brown, and other fur as light yellow-brown or tan.

 

[zinfamous]

Flying squirrels have pink fluorescing fur!

https://www.iflscience.com/plants-a...ve-glowinthedark-hot-pink-fur-under-uv-light/

The finding is cool but then the reporter goes on to speculate on why this might be and completely misses the point that squirrels don't have UV lights to show off their cool pink fur. I propose we remedy this.

A lot of birds can actually see in the UV spectrum, so I wonder if it has something to do with that? (I don't think raptors can, though, which would make the argument relevant a prey-predator adaptation)

I should mention that I did not read the link.

 

[IronWing]

A lot of birds can actually see in the UV spectrum, so I wonder if it has something to do with that? (I don't think raptors can, though, which would make the argument relevant a prey-predator adaptation)

I should mention that I did not read the link.

The issue with the reporter's speculation is that there is no UV light source at night that would trigger the fluorescence.

 

[darkswordsman17]

I think the thread title should be changed to "...: when OP can't read the article"

It was the researchers speculating that stuff, not the writer.

 

[lxskllr]

They should have ground effects under their glide flaps. That would look pretty cool. The owls would appreciate it too.

 

[FluorescentSquirrelLady]

Hello everyone! Thank you guys for your interest in our recent study. I'd love to clarify any questions! First of all I should say that we have no idea why they appear fluorescent. Typically in nature, things evolve for a reason, but not always. We talk about several different hypotheses in our paper that outline some ideas that could explain this fluorescence. Two of them directly involve their environment, which I'll briefly describe. Even though the intensity of the sun decreases in the winter, the proportion of UV-B radiation may double compared to summer. In addition, the snow reflects these wavelengths, making them more prominent in the environment. Also, certain times of day have different proportions of UV in the environment. It just so happens that proportions are highest during crepuscular/nocturnal times of day, when the flying squirrels are most active. They also have uniquely transparent eye lenses that let these UV wavelengths through their eyes; but the real question is, does their brain process this information (can they see it)? There are so many more questions than answers at this point!

 

[Red Squirrel]

Maybe this is evolutionary so that air traffic control can see them better at night, thus they are less likely to get hit by planes.

 

[IronWing]

Hello everyone! Thank you guys for your interest in our recent study. I'd love to clarify any questions! First of all I should say that we have no idea why they appear fluorescent. Typically in nature, things evolve for a reason, but not always. We talk about several different hypotheses in our paper that outline some ideas that could explain this fluorescence. Two of them directly involve their environment, which I'll briefly describe. Even though the intensity of the sun decreases in the winter, the proportion of UV-B radiation may double compared to summer. In addition, the snow reflects these wavelengths, making them more prominent in the environment. Also, certain times of day have different proportions of UV in the environment. It just so happens that proportions are highest during crepuscular/nocturnal times of day, when the flying squirrels are most active. They also have uniquely transparent eye lenses that let these UV wavelengths through their eyes; but the real question is, does their brain process this information (can they see it)? There are so many more questions than answers at this point!

First, thank you for signing in and welcome to our forum!

It is interesting that the squirrels' lenses pass UV and I am curious if they can see into the UV spectrum. It wouldn't really factor into the fluorescent fur as the fur is emitting in the visible spectrum but is definitely something worth exploring in its own right.

Watching fluorescent scorpions and geckos under UV light, one sees that the scorpions and geckos appear to detect the UV light itself and that they do not like it. I could see fluorescence in the eye as a means of indirectly detecting UV. Human corneas fluoresce under UV light and the effect is detectable. I'm not seeing why there would be a connection between fluorescing fur/skin/exoskeleton and detecting UV though.

On the fluorescing fur, have you identified the chemical that is fluorescing? If so, does the chemical have any other identifiable function in the fur? It may help answer the question of whether the fluorescence is a feature or a side effect. If you have a link to the full paper I am interested in reading it.

 

[shortylickens]

Is Mister Burns as fault here?

 

[William Gaatjes]

I might be mistaken, but most birds can see ultraviolet.
I do not know if some birds of prey are predators of squirells . Owls perhaps?

When thinking about that, may be interesting to see how much the coat of the squirrel lights up during nocturnal light.
Might be a side effect. Or some clever use for the squirrels to distinquise a bird of prey versus a flying squirrel.
Which would only work if the squirrel itself can see uv as well.

And of course, does only the abdomen reflect and the back not ?

 

[darkswordsman17]

Gotta love the internet and how it makes stuff like being able to directly interact with researchers possible. I agree, I'd love updates if you find out more info (and hope to see this on nature shows/documentaries talking about things like this).

And OP, kudos for admitting your error on blaming the writer. To be fair to you, reporting on science related topics, especially when it involves hard science with studies and other that doesn't always make for reporting easy, has been lacking in analysis (and often included rampant speculation), and warranted legitimate criticism. But the media I think has evolved some - although plenty of times not enough. But there are more science focused sites - and the site you linked to wouldn't surprise me if it has actual scientists doing some of the reporting.

 

[FluorescentSquirrelLady]

The internet really is crazy... I'm glad that we can reach out and talk to people to clear up any misunderstandings! First I'll mention that, like all news, it's not terribly accurate. They tend to shape their story to fit their needs. For example, we have never provided the term "glow-in-the-dark," but they still used it. As inaccurate as it is, it's "clickable" on social media, so they went with it. The Nat Geo article actually provided a quote from someone saying, “It’s surprising that they did not test more of the species that represent the rest of the flying squirrel subfamily.” Well, we did; but they left that part out. In reality, what the reporters say is only a sample of what actually happened.

William, to answer your question: Yes, many birds can see ultraviolet wavelengths and this has been documented. There are a variety of reasons behind this. In addition, it is predominantly their undersides that fluoresce! This was so fascinating to me. It's basically their cream undersides that fluoresce pink when under UV light. If we part the darker fur on the dorsal surface, it often fluoresces too, but not as readily as the ventral surface. People are beginning to share pictures on Instagram of their living squirrels in UV, so you can check there for images to see what I'm talking about.

IronWing, you definitely have valid thoughts, and they're the same ones that we've been contemplating. Can Glaucomys see their own fluorescence? Can their predators? In short, we don't know. It will likely take a behavioral study to confirm. Fluorescence is simply when a substance absorbs a wavelength and emits a longer one. In this case, it's UV to visible. So, for our eyes, there is clearly a difference between their UV light-exposed fur and natural light fur. However, you are definitely correct that at this point, we have no idea how the squirrels portray this, if at all. But with that being said, we do know that Glaucomys are anomalies amongst the Sciurids for having eye lenses that let through UV. For this reason, we speculate that it's possible that they could be seeing some variation in fur where the fluorescence is and isn't. And then this opens the door to, why? What is the ecological significance?

 

[William Gaatjes]

This internet really is crazy... I'm glad that we can reach out and talk to people to clear up any misunderstandings! First I'll mention that, like all news, it's not terribly accurate. They tend to shape their story to fit their needs. For example, we have never provided the term "glow-in-the-dark," but they still used it. As inaccurate as it is, it's "clickable" on social media, so they went with it. The Nat Geo article actually provided a quote from someone saying, “It’s surprising that they did not test more of the species that represent the rest of the flying squirrel subfamily.” Well, we did; but they left that part out. In reality, what the reporters say is only a sample of what actually happened.

William, to answer your question: Yes, many birds can see ultraviolet wavelengths and this has been documented. There are a variety of reasons behind this. In addition, it is predominantly their undersides that fluoresce! This was so fascinating to me. It's basically their cream undersides that fluoresce pink when under UV light. If we part the darker fur on the dorsal surface, it often fluoresces too, but not as readily as the ventral surface. People are beginning to share pictures on Instagram of their living squirrels in UV, so you can check there for images to see what I'm talking about.

IronWing, you definitely have valid thoughts, and they're the same ones that we've been contemplating. Can Glaucomys see their own fluorescence? Can their predators? In short, we don't know. It will likely take a behavioral study to confirm. Fluorescence is simply when a substance absorbs a wavelength and emits a longer one. In this case, it's UV to visible. So, for our eyes, there is clearly a difference between their UV light-exposed fur and natural light fur. However, you are definitely correct that at this point, we have no idea how the squirrels portray this, if at all. But with that being said, we do know that Glaucomys are anomalies amongst the Sciurids for having eye lenses that let through UV. For this reason, we speculate that it's possible that they could be seeing some variation in fur where the fluorescence is and isn't. And then this opens the door to, why? What is the ecological significance?

I wonder if it is a means to recognize owls. Owls fly silently and probably have feathers that reflect uv. Here is a thought :
If Glaucomys can really see uv. They do not need to see the flourescence, because they can see the uv reflecting of the feathers of the owl itself.
The interesting part is, how does the fur look like when seen through a camera that is sensitive to uv in a similar manners as a Glaucomys may see it.
Perhaps the fluorescence is a nice side effect for us to see but not for Glaucomys.
Just a thought.