Spineless Samurai

When the annual cicadas emerge each summer their tymbals vibrate at arboreal drumming circles all over town.  The beats bounce and reverberate against hard city surfaces; during a crescendo, I swear I can feel the buildings and sidewalks pulsing like wings, like a heart. Yet, despite the percussive nature of this invertebrate orchestra, to my ears the cicada’s summer song evokes the kokyū—a traditional Japanese string instrument played with a bow.

This may be due to the fact that I imagine cicadas as miniature ronin, masterless six-legged samurai, stoic and single-minded, clad in intricately constructed armor of lacquered plates and scales. Of course, several beetle species call to mind this 12th-century warrior class, and I’m not the only one to see the resemblance. Rhinoceros beetles (Allomyrina dichotomy), for example, are known in Japan as a kabutomushimushi, the Japanese word for insect, and kabuto, which refers to the helmet worn by samurai (and the inspiration for Darth Vader’s visage).

It don’t know if it’s an example of the sincerest form of flattery or an unconscious imitation, but biomimicry—biological features or processes used as inspiration for beneficial products and practices— is an old technique that’s experiencing resurgence. Humans have long taken cues from the successful strategies of other animals. Indigenous cultures incorporated the characteristics of nonhuman animals into hunting tactics and rituals; composers have used all manner of musical instruments to simulate birdcalls and other nature sounds; superheroes like Spider-Man and Batman are pretty shameless about co-opting the special powers of their totem animals.

Then there’s warcraft. It’s hard to miss the resemblance between certain insects and the body armor worn by human warriors. From my perspective, there’s a natural synergy between invertebrates, who need a rigid external sheath for support and protection due to the absence of an internal skeleton, and Homo sapiens, who need prosthetic exoskeletons to protect our vulnerable bodies from the increasingly deadly technology imagined and fashioned by members of our own species—first flint arrowheads, then copper maces, bronze spears and daggers, iron javelins and swords, cannons and shrapnel, steel rifles and handguns, and eventually weapons that make any kind of armor irrelevant.

Chemical warfare is common in the insect world, and humans have readily adopted the same strategy against both macroscopic and microscopic opponents. In human enterprises, poisons do generally deliver short-term success; however, the initial win is usually followed by long-term health and environmental losses. This is particularly true when chemistry is used against presumed enemies with high reproduction rates… for example, insects and bacteria.

In most biological populations, there will usually be at least a few members strong or lucky enough to survive the application of toxins. Those individuals become the progenitors of the next generation, passing along their protective genetic code and, over time, rendering the chemical weaponry powerless. That’s how natural selection produces organisms well suited to their environment, and that’s why chemical deterrents always have a limited shelf life… against insects and bacteria, anyway. Less than 150 years after the introduction of antibiotics, hospitals and medical personnel are fighting resistant bacteria, including methicillin-resistant Staphylococcus aureus (MRSA) and multi-drug-resistant Mycobacterium tuberculosis (MDR-TB), and attempting to do so with a limited alternate arsenal.

As a result, biomimicry is shrinking to nano-scale. Researchers are investigating new ways to protect human bodies from bacterial enemies, and certain insects have proven to be adept at mechanical antibacterial warfare. Think samurai on a microbial level.

In 2013, a team of researchers from Australia and Spain discovered that evolution has armed the clanger cicada (Psaltoda claripennis) with an elegantly simple defense against infection worthy of a kendo master. Clanger wings are covered with nano-pillars—aka tiny spikes.

Initially, it was assumed this pointed texture worked like a bed of nails—a hapless bacterium lands on the wing, stretching and sagging into the crevices between the spikes, and as gravity does its thing the pathogen’s skin tears, rendering it incapable of reproduction. Earlier this year, though, a group of Australian and Nigerian researchers proposed that truth is, once again, stranger than fiction… or at least as inventive as a movie villain.

Bacteria adhere to surfaces and each other by secreting finger-like structures called extracellular polymeric substances (EPS). These natural polymers allow the organisms to form biofilms on plant roots and fruit, fish and boat hulls, teeth and gums, plumbing pipes and medical catheters, even hot alkaline spring waters and glaciers—in other words, nearly any surface we know of except a nano-textured insect wing.

If the bacteria on a clanger cicada wing would stay put, they would likely deform but survive. If they move, though, those pillars subject the EPS to shear forces, ripping the external membrane and causing the bacteria to deflate like a balloon due to fatal leakage of the cell’s contents.

Regardless of how these nano-textured surfaces (NTS) kill, their potential as models for developing chemical-free, non-toxic antibacterial materials is undeniably exciting.  One of the first proposed products to utilize NTS was a coating that could be applied to countertops, doorknobs, railings, bus straps, subway poles, sinks, commodes, and even money. An Australian manufacturer of medical implants has acquired the patent, seeing potential for using this technology to reduce the chance of post-surgical infection. Since the killing mechanism is mechanical, devices coated with nano-textures could bypass the clinical approval processes required for chemical treatments, reducing the time and cost to bring these products to market.

Additional research has revealed that clanger cicadas aren’t the only winged insects armed with antibacterial nano-patterns, nor are they the most efficient.  The cicada’s NTS only kills gram-negative bacteria, but the wings of a fiery skimmer dragonfly (Orthetrum villosovittatum) have an NTS that is equally effective at killing both gram-negative and gram-positive pathogens. 

The nano-scale needles formed by black silicon have been tested in the lab and appear to have antibacterial properties similar to those of dragonfly wings. However, scientists aren’t yet sure why nano-patterned wings provides such a powerful defense, or how to replicate it for commercial use. That should come as no surprise given the nature of warfare, on any scale. It’s the Way of the Sword, and a samurai never reveals all of his secrets.

Every summer, people complain about cicadas but if insect wing nano-pillars become the next penicillin they may change their tune. Personally, I find the droning soundtrack soothing. I like knowing that, aided by sodium-yellow streetlights, spineless samurai are keeping watching through the night. Their kokyū lullaby floats past the gingko tree leaves, slips through my window screen, and into my dreams.


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© 2018 Next-Door Nature. First published at the Center for Humans and Nature’s City Creatures blog.  Reprints welcomed with written permission from the author. Thanks to the following photographers who made their work available through the Creative Commons license: Boaz Ng, Walters Art Museum, NFG photo, Mike BitzenhoferPaul Balfe, and tami abigador pearson.

Bull Session

I say potato, you like potahtos. You wear pajamas, I wear PJs. And a rose by any other name, we’re told, would smell equally sweet. So does it really matter that we all agree on what to call an American bullfrog? 

“HELL, YEAH!” 

That’s the collective cry of taxonomists around the globe raising their voices in indignant protest. (Yes, these are men and women of strong, science-based convictions.) You see, to a biologist who studies the classification of organisms, names are not at all trivial… but they should all be binomial.

Swedish botanist Carl Linnaeus is credited with introducing this ubiquitous classification system, based on bestowing a unique two-word Latin name upon each species, precisely to avoid the kind of misunderstandings that arise when you say ersters and I say oysters.

Or, for example, when one scientist is talking about a fish using one of its common names, “dolphin” (Coryphaena hippurus, aka mahi-mahi, dorado, pompano), and another scientist hears “dolphin” and thinks of a perpetually-smiling bottlenose marine mammal (Tursiops truncatus).

And yet, despite Carl’s best efforts, disagreements persist. As in the case of the American bullfrog, whose official Latin name (Rana catesbeiana or Lithobates catesbeianus, depending on whom you ask) is more likely to be disputed and cause confusion, ironically, than its common name.

The quibble over nomenclature began about 10 years ago and quickly became a quarrel. Darrel Frost, Herpetology Curator at the American Museum of Natural History, suggested a conceptual leap that would divide members of the genus Rana, which includes bullfrogs, into nearly a dozen new genera. Many of Frost’s colleagues, unconvinced that his argument held water, refused to jump into the newly proposed systematics pond.

In response, feelings, opinions, and counter-claims have been aired publicly in peer-reviewed journals. Several years ago, a group of international researchers created a consortium to promote their own preferred adaptation of the froggy family tree. The taxonomy community still hasn’t managed to harmonize this chorus, which is why she says Rana and he says Lithobates.

But hold on… let’s not call the whole thing off just yet.Because, of course, a bullfrog doesn’t need a taxonomist to know exactly who he or she is… once s/he reaches a certain age, anyway.

Sure, there may be some gender ambiguity early on but that’s common among young amphibians. Their sex is determined genetically, although research suggests that for many frog species, exposure to environmental estrogen or variations in water temperature during tadpole-hood can induce male-to-female or female-to-male transitions. Self awareness doesn’t always come easily, and it can take some time for those gender identity questions to work themselves out. Bullfrog development is relatively slow—one to three years from egg to adult, and another two years to reach sexual maturity.

By the time they’re ready to procreate, however, males and females have definite, discernible physical differences. Males are smaller than females, their tympana (external eardrums) are larger than their eyes, and when in breeding condition their throats are yellow; female tympana are equal or smaller in size than their eyes, and their throats are white. There are behavioral distinctions as well—male bullfrogs are territorial over the summer mating season, and quite vocal about it, too; females are relatively silent, although older gals have been known to sing along with the guys. (I have a sneaking suspicion their favorite tune is If I Were A Boy.)

Ok, ok… life, in all it forms, is full of uncertainty and differences of opinion, at the laboratory bench and the water’s edge. But can we all come together on this much, at least? That the creatures featured throughout this post are:

a. Amphibians

b. Bullfrogs

c. Cool.

Everything else is neether/nyther here nor there.


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© 2018 Next-Door Nature. Reprints welcomed with written permission from the author. Thanks to the following photographers who made their work available through the Creative Commons license: Mark Beckemeyer, LadyDragonflyCC, Greg Schechter, Rick Cameron, and Kaibab National Forest.

Telephone

This university town is always less crowded during the summer. Most students are at home or on summer internships, faculty and graduate students are using the break to slip away for some R&R or doing research at field sites, and there are no home football games to bring in alumni and supporters of the opposing team.  While I enjoy the school year, and recognize how much Blacksburg depends on the university and related personnel, I do my best to pause and catch my breath from mid-May to mid-August.

That includes plenty of walks with my wire fox terrier, Dash, along a leafy section of the Huckleberry Trail, a former railroad easement. Tt’s rare for Dash and I to have the Huckleberry trail all to ourselves, at least not for very long. Usually we share with cyclists, runners, and other dog-walkers.

But one mid-July day was an exception. I guess we must have left a bit later than usual, but regardless of the reason, the trail and surrounding suburban backyards were quiet enough for me to hear a feathered fellow shouting his heart out from the power lines above.

I peered skyward and saw the black, white, and terra cotta of an Eastern towhee (Pipilo erythrophthalmus)). I’ve read descriptions of this bird’s call as “Drink your tea!” but to my ears it sounds like, “Drink your tea-hehehehe!”

I stood still for as long as Dash could stand it, enjoying the sight and sound of a serious sparrow with a major case of the giggles. Then we picked up the pace and continued walking.

 

 

Several minutes later… more giggling. Were we being followed? Most likely is was a different individual; it was breeding season, after all, and males tend not to stray far from home base and the Mrs.

 

 

 

 

Further down the trail… more tea, more giggles. I felt like I was hearing a musical baton passed from one bird to the next in an auditory relay…

 

 

 

 

Drink your tea-hehehehe!…

 

 

 

 

 

Drink your tea-hehehehe!…

 

 

 

 

 

Drink your tea-hehehehe!

 

 

 

 

I can recognize a game of Telephone when I hear it! In this case, though, all of the players were excellent listeners who repeated the phrase exactly, with perfect fidelity and zero degradation. Since garbled messages are the whole point and fun of Telephone, I wasn’t sure why all these towhees were laughing.

I’ve heard recorded birds calls I couldn’t distinguish by ear but the sonograms (graphical representations of sound) showed clear variations my hearing wasn’t sensitive enough to notice. Maybe if I had Towhee ears I’d be in on the joke.

When Dash and I returned home I had the strangest craving for a cup of tea (strange because I don’t even like tea).


Who’s playing telephone in your neighborhood?  Share your experiences and comments below! And if you’d like a little Next-Door Nature delivered right to your inbox, click the “subscribe” link in the upper right-hand corner of this page to receive notifications for new posts!

[© 2018 Next-Door Nature, Sidewalk Zendo. Reprints welcomed with written permission from the authorThanks to the following photographers for making their work available through the Creative Commons license: Pat Gaines, Alberto_VO5, devra, Mike’s Birds, Amanda, Ken Schneider, marneejill, and Keith Carver.]

Street Creatures Has Moved!

Six-legged tribute and political commentary in the form of a dragonfly in Bethnal Green, London, UK (Photo by Maureen Barlin, cc by-nc-nd 2.0).

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Vice Squad

I was just trying to help, I swear.

In fact, the primary directive in wildlife rehabilitation is: First, do no harm. But the indignant male northern cardinal (Cardinalis cardinalis) I had just lifted out of a shoebox clearly interpreted my attempts to do a thorough but gentle intake exam as disrespectful. He spat a curse at me, and before I could blurt out an apology, he clamped that bright orange vice-like beak down on the webbing between my thumb and forefinger with more force than seemed plausible for a creature that weighed less than 2 ounces (57 g). 

There we stood—me holding him and trying not to squeeze, him holding me and trying to squeeze with all of his might. I watched a blood blister forming beneath his pincer but there wasn’t much I could do about it. Any attempt to pry him from my hand risked adding to his injuries. I could only try to remain as still as possible, take deep breaths, and wait for him to let go… even though he appeared firmly cemented in place.


Cardinals are year-round residents in much of the continental U.S., from the East Coast westward into Nebraska, Kansas, Texas, parts of New Mexico, Arizona, and southern California. Familiar and conspicuous, with an easy-to-recognize crest and stop-light bright plumage, even in winter, this species is a perennial favorite of backyard feeder enthusiasts and beginning birders. This species is known to be a courageous defender of both offspring and territory, which may be why it was chosen as the mascot for a couple of national sports teams, and for seven different states.

Songbird beaks often provide a clue, or a blatant disclosure, of the owners’ food preferences, especially if the species is a fussy eater—for example, primarily nectar, or meat, or in this case, seeds. There’s more than one way to crack a hard shell and evolution has equipped other granivores with distinctive but equally effective beak shapes. Even so, the cardinal’s short, thick, cone-shaped bill is typical of an avian seed-eater.

Which is not to imply that these black-masked bad-ass birds demand a solely grain-based diet; approximately 10% of their calories come from fruits, flowers, maple sap, and invertebrates. Moreover, their young are fed insects almost exclusively until they’re old enough to leave the nest and digest seeds.

Hatchlings cardinals don’t start life equipped with the same vice-grip their elders wear on their faces (rather than in tool belts at the waist). Given the sibling rivalry for Mom and Dad’s attention whenever they bring home groceries, it’s probably for the best that the youngsters don’t have access to pinching pliers until after they fledge; pushing and shoving are dangerous enough when the nursery is a twig cup perched precariously in the crook of a tree branch.

Eventually, the baby redbirds bills do morph into their final adult size and shape, although for a while the their adolescent nose may look out of proportion to the rest of their head. Hey, being an awkward teen is all part of growing up. It builds character, or so they say. 

With daily compulsory practice (at least if they want to eat) it doesn’t take long before those gawky bills are wielded like a finely crafted tool that quickly converts a feeder full of sunflower seeds into a pile of empty shells… or, very nearly brings a well-meaning wildlife biologist to her knees.


Back at the rehab center intake desk, the good Samaritans who had handed me the shoebox—a young mother and two small children—watched as I stood stock still, a bright red songbird pretending to be a pair of locking forceps stuck to my hand, struggling to hold back tears of pain (and four-letter words).

It’s been 20 years since I worked at the TWRC Wildlife Shelter in Houston, Texas. I’m not at all sure how long it took for the cardinal to release his grip… what feels like least a half-hour in memory was probably less than 3 minutes in real time. Luckily, there’s no scar on my hand, but my cardinal encounter did leave a lasting mark; the memory of that fierce feathered vice is riveted to my brain.

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[Thanks to the photographers who granted permission to use their photos, and to those who made their work available through the Creative Commons license: John Flannery, Fred Faulkner, Sasha Azevedo, Kenneth Cole Schneider, and John Flannery© 2017 Next-Door Nature. Reprints welcomed with written permission from the author.]

Wingsuit

Southern flying squirrel (Glaucomys volans), © 2014 Peter Harrill, used with permission

Is there any non-human skill people covet more passionately than the ability to fly?

Understandably, early aviation experiments centered around mimicry of birds, complete with flapping arms that were usually covered in feathers. The Greek legend of Daedalus and Icarus is a familiar example, but plumage continued to be part of the trial-and-error approach through the first years of the 19th century, when a tailor named Albrecht Berblinger constructed an ornithopter and then took an ill-fated plunge into the Danube. Those daring young men with their dreams of flying machines… they just didn’t understand the concepts of thrust, lift, and drag, and they couldn’t let go of the idea that soaring requires feathers.

I guess Saturday mornings with Rocky and Bullwinkle were not a part of their childhood.

Skip ahead in the history books about two hundred years, during which heavier-than-air flight went from foolish fantasy to fleetingly airborne, to semi-reliably aloft, to acrobatic enough to decide the outcome of a World War, to commonplace as ~30,000 commercial flights per day in the U.S. in 2017.

And yet…

Aviation advancements and inventions during the greater part of the industrial age were about balloons and dirigibles and planes, i.e., aircraft; human beings remained firmly planted on terra firma unless they could climb inside or hang from some kind of apparatus.

It’s hard to point to a specific aeronautic adventurer as the first to see a flying squirrel, recognized the similarities with their fellow mammal, connected the dots, and think, “Eureka! A wingsuit!” But no one lucky enough to have seen one of these big-eyed nocturnal windsurfers could fail to notice the resemblance to the modern flying suits that have finally allowed human beings to fly free as a bird squirrel, unencumbered by gondola, scaffolding, or fuselage.

Of course, strictly speaking flying squirrels don’t really fly, and neither do the people wearing a wingsuit.

They glide.

The wingsuit mimics a flying squirrel’s patagium—loose folds of skin that span the space between forelimb wrist and hindlimb ankle on either side of the body. Spreading those limbs into a jumping jack X, the furry membranes stretch into a rectangular shape that allows the tiny BASE* jumpers to propel themselves into the air and then slide down the sky at a 30-40 degree angle controlled fall.

© 2008 Steve Collins, used with permission

A long, flat tail is critical for controlling that fall. Serving as a rudder, it allowing 90 degree turns around mid-flight obstacles. The tail is used for landing, too; on the approach, the tail is raised to an upright position while, at the same time, all four limbs move forward to form a kind of patagium parachute. Together, these actions create enough drag to tip the animal’s head and body up as it prepares for impact with a tree trunk or branches, a bird feeder, or a building.

Northern flying squirrel (Glaucomys sabrinus) © 2015 Jukka Jantunen, used with permission

The New World is home to three species of rodent flyboys and flygirls: Northern (Glaucomys sabrinus); the recently differentiated and designated Humboldt’s (G oregonensis); and Southern (G volans). There’s some range overlap between Northerns and Southerns, but the two species are relatively easy to distinguish. Northerns are larger, but the belly of the beasts provides a much more notable difference; the underside of a Southern flying squirrel is creamy white, while Northern flying squirrels are beige below with darker roots.

Humboldt’s flying squirrel

There’s range overlap between Northerns (found from Alaska to Nova Scotia down to Utah and North Carolina) and Humboldts’ (whose limit their travels from British Columbia down into southern California) as well. However, the two are close enough in physical appearance and behavior that it took an examination of their DNA before scientists realized earlier this year (May 2017) that they were looking at not one species, but two. Humboldts’ have been described as smaller and darker than Northerns, but the fact that it took so long for the former to be recognized as distinctive (Southerns were first described in 1758, Northerns in 1801) suggests to me that one would have to do a mighty up-close-and-personal examination to make a positive ID.

All three varieties of Glaucomys have one important feature in common: they’re more risk-averse than you might have assumed. Riding the wind wearing a wingsuit is a dangerous activity for humans — one severe injury for every 500 jumps, according to one study, despite advances in materials, design, and training — but it’s just another day in the life of a flying squirrel. That’s not to imply they never miscalculate a distance, or botch a landing, or are immune from injury (or worse), but they do have concerns beyond thrust, lift, and drag, or changes in wind speed and direction.

Which is why, immediately after sticking the landing, a flying squirrel will scurry quickly to their nest hole, or the other side of the tree, or at least toward a deeper shadow. BASE jumpers and skydivers rarely have worry about avoiding predators waiting in the wings.

[Thanks to the photographers who granted permission to use their photos, and to those who made their work available through the Creative Commons license: Richard Schneider, and Barbogast. The painting of Icarus and Daedalus is by Charles Paul Landon, and the drawing of a New World flying squirrel is by Charles Henry Dessalines d’Orbigny, currently in the University of Washington’s Freshwater and Marine Image Bank; both images are in the public domain. © 2017 Next-Door Nature. Reprints welcomed with written permission from the author.]

*BASE is the acronym that stands for the four categories of fixed objects from which one can jump: building, antenna, span (bridge), and Earth (cliffs).

Long-stemmed

Daddy longlegs are the jazz cats of the arachnid world!

This realization came to me as I watched a single backlit note poised on a broken music staff bebop across the asphalt path in front of me. A soundtrack of jazz piano greats immediately began to play in my head — Willie “The Lion” Smith, Thomas “Fats” Waller, Art Tatum, Thelonious Monk, and Dave Brubeck, to name but a few. Chill dudes whose spider-like fingers strode, slid, bounced, and stomped across the keys.

Jazz has evolved and diverged from it’s start in the late 19th century as  ragtime and Dixieland into a genre so diverse it can be difficult to define, or even to list all the variations: Swing, Cool, West Coast, Modal, Free, Fusion, Funk, Cu-Bop, Post-Bop, etc.

The harvestmen, as daddy longlegs are also known (that even sounds like a 1950s jazz band, doesn’t it?) have an even longer and more impressive history. They’re a vast, improvisational set that spans millions of years and many taxonomic octaves, with over 6,500 named species worldwide (experts estimate there may actually be more than 10,000). And while not all the players in this big band have long legs, the ones who hangout in my neighborhood— eastern harvestmen (Leiobunum vittatum)— are definitely long-stemmed.

These invertebrate daddy-o’s are arachnids but they are NOT spiders; they’re more closely related to mites and scorpions.  Harvestmen don’t have a spider’s tiny waist… or venom… or silk (so no webs)… and they have only two eyes instead of eight.

Jazz musicians need to maintain their instruments to get the best sound; piano hammers need to be voiced, strings tuned, reeds moistened and valves lubricated.  Daddy longlegs are similarly serious about the tools of their trade, cleaning each leg after a meal by threading them through the pincers by their mouths.

Harvestmen are a gregarious lot who periodically congregate in the hundreds or even thousands. Scientists have suggested these spontaneous jam sessions might occur in response to climatic conditions or provide some protection against predators… but it’s pretty clear they aren’t making music (that can be detected by the human ear, anyway).

Members of Order Opiliones are exceptional even among arachnids. They can swallow small pieces of solid food, whereas their cousins are limited to a liquid diet. Conversely, daddy longlegs sip oxygen through their legs into a trachea, while other arachnids respirate through a gas exchange organ called a book lung. That’s probably just a warm-up, though. Like jazz, daddy longlegs are both familiar and mysterious. Little research has been done on these species… and who can say why? Maybe they’re a bit too avant garde to have a large fan base among researchers.

Or it could be the hours they keep and the dives they frequent. See, eastern harvestmen have more in common with jazz pianists than an impressive hand (or leg) span. Say what you will about the pleasures of sitting outside at a warm summer evening festival, lounging on a blanket in the grass while listening to a live performance — you’ll hear no argument from me. But to my mind, jazz is an urban art form, and the smokin’ hot licks happen in basement clubs. An intimate corner, low lights, insulated from street noise, maybe just a little damp…

Now that the kind of gig daddy longlegs’ dig.

 

[Thanks to the following photographers for making their work available through the Creative Commons license: Rob Swatski, Leslie Bliss, Rob SwatskiLuis Fernández Garcia, and schizoform.  © 2017 Next-Door Nature. Reprints welcomed with written permission from the author.]

Vert-de-Gris

Cope’s gray treefrog on a pepper plant. Photo: Alan Howell © 2017, Star Path Images, Used with Permission.

It isn’t easy being green. Kermit the Frog said it, so you know it has to be true.

He’s always seemed a reluctant celebrity, so my guess is that being the most famous Muppet-amphibian on the planet isn’t always a picnic. I wonder whether life would be a little less stressful if, like some of his cousins, Kermit could change from green to another color when he’d rather not be so conspicuous.

North American gray treefrogs know how to be seen and when to blend into their surrounding, shifting the spectrum from bright emerald to peridot, to gold, copper, platinum, silver, and even gunmetal. Since the places they hang out — trees and shrubs in woodlands, meadows, prairies, swamps, suburbs, and cities — tend toward palettes awash with green and gray hues, these arboreal amphibians can keep their sartorial choices simple. 

What looks like a costume change is actually a rather high-tech, cellular-level special effect created by chromatophores. These pigment-containing and light-reflecting cells, or groups of cells, are present in the skin of certain frogs, as well as some reptiles (including chameleons), cephalopods (such as octopi), fish, and crustaceans. Mammals and birds, on the other hand, have melanocytes, a different class of cells for coloration.

Chromatophores are classified based on their hue under white light:

  • melanophores (black/brown)
  • cyanophores (blue)
  • erythrophores (red)
  • xanthophores (yellow)
  • leucophores (white)
  • iridophores (reflective or iridescent)

The process, known as physiological color change, can be controlled by hormones, neurons, or both. Most studies have focused primarily on melanophores because they are the darkest and, therefore, the most visible. When pigment inside the chromatophores disperses throughout cell the skin appears to darken; when pigment aggregates in cells the skin appears to lighten. Either way, you’ve got an amazing makeover, or a convincing disguise, in no time flat! 

There’s even more to the gray treefrog’s ability to assume an alter-ego than meets the eye —what appears to be a single species is actually two very close relatives: Hyla versicolor, aka Eastern, although there’s a long list of pseudonyms from which to choose (there are more ways to hide than blending into the substrate); and Hyla chrysoscelis, aka Cope’s (which also has a couple of nicknames but not as many as H. versicolor).

Cope’s and Eastern are equally skilled at clinging to and climbing slick surfaces using large toe pads that secrete mucous, creating surface tension. It’s not uncommon to find one plastered against a window pane (allowing for an interesting view of their nether-regions). Both species prefer a diet of small insects, spiders, and snails. Both hibernate under leaves, bark, or rocks. Well, “hibernate” sounds a lot more cozy than the reality… which is that their bodies pretty much freeze and their lungs, heart, brain, and other organs stop working until they thaw out and reanimate in the spring. It’s a pretty nifty chemical trick, on par with being able to transform your complexion at will. 

Kermit has an unmistakable personal brand, but distinguishing H. versicolor from H. chrysocelis visually is just about impossible. Both Eastern and Cope’s are relatively small (1.5—2.0 in/3.5—5 cm), and the adults are often mistaken for younglings. Both wear a sweep of bright citrus-orange along the inseam of their hind legs (a signature shade is all the rage, you know).  Females of both species are usually (but not always) larger, with a ladylike white throat. During the breeding season, males have a macho (make that hipster, since it resembles a beard) black, gray, or brown throat. Guys sing. Gals swoon, but don’t sing along.

The ranges of these two species overlap, but Cope’s are more widely distributed. If you find a gray treefrog in North Carolina or Georgia, you can be reasonably certain it’s a Cope’s, but if you’re in Iowa or Pennsylvania, all bets are off. The only risk-free way to know for sure is to do a DNA test — Cope’s are a diploid species, meaning they have two sets of chromosomes, one from each parent (for a total of 24); Easterns are a tetraploid species, meaning they have four sets of chromosomes (for a total of 48).

Now, some frog call connoisseurs claim they can detect variations in breeding calls, and that Cope’s treefrogs have a faster and slightly higher-pitched trill than Easterns. But the call rates of both species change with ambient temperature… so color me skeptical.

[Postscript:  What kind of frog is Kermit? While I’ve never found a definitive answer to this question, I always assumed that because he was created/discovered by Jim Henson, he was probably Hyla muppetalis or Rana hensonii… something like that. However, in 2015 Brian Kubicki of the Costa Rican Amphibian Research Center discovered a frog who, if not the same species, must at least be a first cousin, or possibly Kermit’s doppleganger.]

Diane’s bare-hearted glass frog (Hyalinobatrachium dianae). Photo: © Brian Kubicki, Costa Rican Amphibian Research Center, Used with Permission

[Thanks to the photographers who granted permission to use their photos, and to those who made their work available through the Creative Commons license: Dave Huth(composite of color variations), , Chiswick Chap & CheChe, (melanophores schematic), Alan Wolf, Andrew Hoffman, and Douglas Mills© 2017 Next-Door Nature. Reprints welcomed with written permission from the author.]