GLOWING PINK FLYING SQUIRRELS: Biofluorescence Revealed

Southern Flying Squirrels, Glaucomys volans, glowing hot pink on their underbellies when illuminated by a 365 nm UV flashlight, in a rare phenomenon known as biofluroescence

I awoke last night at midnight to flashes of light from a motion sensor floodlight on our deck. I wasn’t thinking of prowlers, because I suspected the flashes of light were triggered by Southern Flying Squirrels coming to visit for the sunflower seeds I had tossed out just before going to bed.

I crept downstairs and carefully opened the sliding door, letting in frigid February air. The deck light came on briefly, enough that I could see the tiny squirrels dashing up through an opening in the deck around a huge Northern Red Oak. Each squirrel would come up, grab a sunflower seed, then dash down the tree trunk out of sight. This happened so fast that I couldn’t see how many squirrels there were, though at one point I saw three. There may have been more. On this night they were nervous and did not stop long enough for any photos.

We’ve had Southern Flying Squirrels at our home in Michigan each winter, and I’ve photographed them at night several times using incandescent lights on the deck. They made for good photographs, with their gray-brown fur and a cuteness factor of huge bulging eyes and little pink lips, but their coloration was subtle to my eyes and essentially no different from most mammals, which are colored for camouflage rather than display.

Then scientific knowledge suddenly changed. About four years ago a Wisconsin forestry professor, Dr. Jonathan Martin at Northland College, was in the woods at night looking up toward the forest canopy with an ultraviolet flashlight for lichens and other fluorescing lifeforms, when a hot pink missile glided overhead. He identified this as a Northern Flying Squirrel, and its normally white belly lit up hot pink in ultraviolet light. He found this astounding, and asked a colleague to investigate flying squirrel skins in a couple of museum collections to see if the phenomenon could be confirmed. It turned out that in those collections, the bellies of all three species of North American flying squirrels–Southern, Northern, and Humboldt’s Flying Squirrels–glowed bright pink under UV light. Even specimens over 100 years old. Male and female, young and old, they nearly all glowed.

Since we have easy access to flying squirrels at our home in Central Michigan, I decided to observe this phenomenon for myself. I obtained a 365 nm UV flashlight that is powerful enough to look almost into the treetops and began looking at these squirrels on nights they chose to come to our feeding station. They don’t come every night, but when they do I often get up in the middle of the night to observe and try to photograph them. It isn’t easy to photograph little nervous squirrels by a relatively dim (to our eyes) UV light, but I’ve had some success represented by the pictures here.

Southern Flying Squirrel showing biofluorescence under UV light on the left, with the same species illuminated by tungsten light on the right. The belly fur changes from off-white to bubblegum pink when struck by UV light.

Why do flying squirrels glow? That is still unknown. What is known is that at dusk, dark, and dawn, the air is bathed in proportionately more ultraviolet light and far less light from the visible spectrum than in daytime. This UV light–when converted to visible light by fluorescence–makes the flying squirrels more visible to each other. This is even more true when snow blankets the forest, since snow reflects UV light. It also appears that flying squirrels’ eyes, unlike ours, can see into the UV spectrum, so this ability may also be involved.

Again: why do they use biofluorescence and UV light at night? There are a couple of possibilities that spring to mind. Based upon the three flying squirrels I observed on that recent February night, I think it’s possible that the squirrels use their bubblegum pink undersides to keep track of each other at night. These squirrels are highly social, with reports of 25 to 50 Southern Flying Squirrels roosting communally in a hollow tree. So why wouldn’t they follow each other to food sources? Some of my pictures show them sitting side by side, dining quietly together on the sunflower seeds I put out. They seem to enjoy a more peaceable kingdom among their kind than do the daytime Eastern Gray Squirrels and American Red Squirrels we also get in Central Michigan. Feeding together also means more big eyes to look for predators–much as goldfinches and other songbirds feed communally as a strategy to detect hawks.

There is another tantalizing possibility for the pink color. Three large owls that also live in this region–Barred, Barn, and Great Horned Owls–also have bellies that fluoresce hot pink under UV light, though their coverings are feathers rather than fur. These owls are the chief predators of flying squirrels. Do the flying squirrels mimic the owls to fool the predacious birds into thinking they are seeing other owls when in the air? Maybe. I find this possible. The fluorescing fur is mostly on the belly and undertail of the squirrels, with just a minor hint of color change on the back and virtually none on the tail. Once a flying squirrel lands on a tree trunk, its back and tail make it almost invisible to predators because the glowing belly is nearly hidden.

Alternatively, perhaps the owls are mimicking the flying squirrels, fooling the little squirrels into thinking they are seeing others of their own kind. This would allow the owls to silently approach the flying squirrels and suddenly grab the little creatures.

Or perhaps all three of these mechanisms are in play: bubblegum pink signals the presence of flying squirrels to each other, but also both disguises them from owls and identifies them to owls, if any of that makes sense. Coevolution at work.

Biofluorescence also extends to the Virginia Opossum in this region, but is apparently unknown in other mammals here. It turns out the phenomenon is new enough that the chemical and physical mechanism is still unknown. I suspect this will be studied in coming years, with possible applications for industry. Or not. Knowledge is its own reward.

I will be watching these creatures over the coming weeks and years, both with and without the assistance of UV light. The mysteries of nature are an ingrained part of my life and I find observations and photography endlessly fascinating.

The photographs above are a good representation of the Southern Flying Squirrel in UV vs visible light. The final photograph shows the deck setting at night where all the pictures were taken, and includes one flying squirrel for scale. Click on the photographs to see them larger.

Here are some other sources that examine this discovery:

Ultraviolet fluorescence discovered in New World flying squirrels (Glaucomys) (Journal of Mammalogy)

Southern Flying Squirrel (Wikipedia)

Flying Squirrels Glow Fluorescent Pink Under Ultraviolet Light (Smithsonian)

OLYMPIC NATIONAL FOREST: Hiking the Upper Dungeness Trail on Father’s Day Weekend

The Dungeness River rushing through the forest

Our weekend backpacking trip led into Olympic National Forest, located on the Olympic Peninsula west of Seattle. This is a lush place, with mosses and every shade of green, as well as a river tinted aqua with glacial flour. It is also a place of silence, where the occasional sounds are the rushing of the river and the dreamlike songs of Hermit Thrushes high in the towering Western Hemlocks and Douglas Firs.

Our hike took us about three miles in, where we set up our tent at Camp Handy. The next morning, we hiked up 1,800 vertical feet to Boulder Camp, then later hiked back down to camp, packed up, and hiked out. Rather that give a sight-by-sight account of the trail, I’ll let the pictures speak for themselves.

Giant Western Hemlocks tower above the Upper Dungeness Trail

I would, however, like to give a shout out to all the Dads who took their families backpacking on Father’s Day weekend. At Camp Handy, there were four other groups in addition to Karen and me. One was a Dad with a teenage daughter, who stopped and chatted with me about where his daughter could learn photography. The second were two men with four young daughters. The third were two men with two young sons. And the fourth was a father with a pre-teen daughter.

This was wonderful that all these Dads were teaching their daughters and sons about backpacking in a beautiful place. All these kids would have come away with new skills and a healthy attitude about experiencing the great outdoors.

I think back to my own father, and all the weekends he spent on Boy Scout trips with his three sons. He was a scoutmaster for several years, and he influenced scores of boys with his interest in nature and his leadership. Thanks Dad: wherever in heaven you are!

And a hearty thanks to all the Dads we saw bringing their children into the wilderness!

Blooming Pacific Rhododendrons line the trail; these are as elegant as the garden varieties that flower so beautifully in the Pacific Northwest

These aren’t rolling stones, because they’ve gathered a great deal of moss

Boulder Shelter is located in a place where giant boulders have tumbled down from the cliffs above (not seen in this picture) and where avalanches have repeatedly mowed down a wide path of trees. It must be a place of uneasy sleep.

In Boulder Shelter: a riff on the old Rolling Stones tune, and an unhappy lady hiker!

Karen led in the making of snowman “Boulder Bob”

A rustic log bridge using a giant Olympic Peninsula tree spans the Dungeness

Oak Ferns all turned at precisely the right angle to the available light–like the precision solar collectors that they are

Avalanche path below Boulder Camp, with Mt. Mystery and Mt. Deception distant in the upper picture

The shape of the leaves echoes the shape of the rapids, at least to my eye

Slime mold Leocarpus fragilis growing on the forest floor among hemlock needles; these little yellow sacs will eventually turn brown, crack open like eggs, and release the spores that bring more little slime molds

Green mosses and the bluish wood rot produced by Fairy Barf lichen (lots of little chunks, you know) on an old log

Shelter at Camp Handy; good for those many days of incessant dripping on the Olympic Peninsula

Looking out from the Camp Handy shelter across the meadow to the willows lining the Dungeness River

Shooting Stars were in full and glorious bloom

Vanillaleaf in bloom; this lovely ground cover is said to have a strong vanilla scent when it dries out; alas, my nose cannot detect this supposedly delicious fragrance

Western White Pine

Emerging leaves of Cow-parsnip

The Dungeness River plunges rapidly, and with beauty, from the Olympic Mountains toward its desired union with the sea

Royal Creek rushes down from Royal Basin, where we’ve had some wonderful alpine experiences in the Olympics

The trail leads through the beautiful forest between Camp Handy and the trailhead

To see my web site, which includes photographic prints for sale, please go to LeeRentz.com (just ask me to email you a small version of a particular photograph you like if you can’t find it on the site; my website is not up to date). 

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February 11, 2009: Jogging at 175 Photos Per Hour; Part 1

I occasionally jog along the Clear Creek Trail in Silverdale, Washington. Although I am a poor jogger with knee and muscle problems, it has been my primary form of exercise for 35 years and I still enjoy each outing.  Sometimes I take a small digital camera with me and grab some photographs along the way.  This day was special, in that I took 295 photographs along my 4 1/2 mile route, stopping every time a potential photograph grabbed me.

These impressionistic photographs were not created by using filters or Adobe Photoshop tricks.  They all look pretty much as they came from the camera, with just a few tweaks of contrast and brightness and color to make them look a bit better on the internet.  They are experimental, and I intend to experiment with this technique in the future, since it gives such a transformative look to an everyday scene.  I will discuss my technique here in the future, but for now you can just enjoy the view.

To see my web site, which includes photographic prints for sale, please go to LeeRentz.com

NEW: To see thousands of my photographs in large file sizes for use in magazines or other printed materials or electronic media, go to my PhotoShelter Website

 

 

 

 

 

 

 

 

December 27, 2008 Into the Mystic Midwest

 

Today I was in the middle of Michigan’s Lower Peninsula visiting family during a Christmas trip. This year the traditional white Christmas visited with a vengeance: it has been a snowy December in this part of Michigan, with nearly 40″ of snow falling during the cold and icy month. But weathermen were predicting a letup from the cold–a front of unseasonably warm air was blowing in, creating a certainty of fog. I love photographing foggy landscapes, so the change of weather was just perfect. Less so the roads.

With my wife and mother nervously accompanying me as I drove our rental car on back roads glazed with ice, I set out to capture the essence of fog blanketing the wintry farm fields and maple forests of central Michigan.  We did a loop from Stanwood to Big Rapids to Mount Pleasant and back to Stanwood, passing through Amish country and the kinds of Midwestern small towns that politicians love to extol as being the heart of America. Though the temperature reached 54°F as we travelled, the sun was never able to burn through the fog. Just for fun, we decided to follow the GPS unit’s voiced guidance in our rental car. In soothing tones, the female voice told us where to turn. But computer woman had never been on snowy Michigan back roads in the middle of winter, and she led us over hilly roads completely covered with ice that had yet to see a salt or sand truck. When she tried to lead us down a road that was, in reality, an unplowed trail, we drew the line. Fortunately, she didn’t get upset at us and simply recalculated our route. Nice lady computer.

The fog was thick in the open hardwood forests, lending an atmosphere of mystery to a day in which tree trunks marched in ever-lightening shades of gray into the distance. Fog shrouds the landscape with quiet, and I think that feeling comes through in my photographs. This type of fog is known as advection fog, and it forms when warm, moist air flows over a snow-covered landscape. As this warm, saturated air chills near the cold ground, fog forms. My mind has a hard time comprehending the scientific explanation of this phenomenon which involves dewpoints at the interface of cold and warm air, but for those who need to know, there is a good website with a succinct explanation: www.theweatherprediction.com

I stopped the car repeatedly to get out and photograph, finding that the road was a sheet of  ice that threatened me with a hard fall.  But I remained upright and took numerous pictures all morning, until my wife and mother in unison shouted “No!” when I tried to park the car on an icy hill and get out one last time to take a picture. I relented under the pressure of their good sense and got back in the car. Good boy!

The fog lasted all day, as did we on our adventure. When we drove home through the dark in early evening, a wind had come up and was blowing the fog sideways across the road at a high velocity. I’m used to driving in blowing snow, with the headlights piercing the mesmerizing and dazzling matrix of billions of big flakes. But I had never before driven through dense and blowing fog, in which the fog line kept disappearing and the headlights penetrated the mist barely a car length ahead. We never had to stop entirely, which was good because the snow was hard and crusted high on the road shoulder. We made it home, exhausted after the drive, but I was happy with my mystic Midwestern pictures of the day. 

When I got home and looked at the photographs, I enlarged several to a high degree.  Only then did I see two White-tailed Deer bedding down in the mist, partially obscured by the trees. When I took the picture I must have been only 40-50′ away from the deer, yet they remained quietly hidden in the forest. It was a day of that kind of magic.

 

To see a variety of my photographic work, including photos for sale, please go to LeeRentz.com

Click on the photographs below for versions with captions.