Tuesday, March 29, 2016

A Conversation with an Indigo Snake Conservationist

Dirk Stevenson is Director of the Fire Forest Initiative with The Orianne Society, a non-profit organization dedicated to the conservation of reptiles and amphibians.  Dirk has worked with the federally threatened (listed in 1978) eastern indigo snake (Drymarchon couperi) since 1990. He initiated mark-recapture studies of indigo snakes in Georgia in 1999, and with colleagues has captured and marked (with PIT tags) over 500 indigo snakes.  Dirk is based near Savannah, Georgia, and conducts field work throughout Florida and the Coastal Plain of Georgia, with a special focus on sites located in the Altamaha River basin (including the Orianne Indigo Snake Preserve) of southeastern Georgia, a notable stronghold for indigos, gopher tortoises and eastern diamondback rattlesnakes.  With colleagues, he has published scientific articles related to indigo snake prey habits, survey methods, population ecology, defensive behavior, and a recent paper that summarizes the status and current distribution of the species.

I recently joined Dirk, on a weekend in late November for a south Georgia indigo intensive search.  During our time together, I conducted an interview of sorts. Below, interspersed in my account of our field time are Dirk’s replies to my questions. 

Dave Steen:  What is special about eastern indigo snakes?

Courtesy Andy Day
Dirk Stevenson:  Indigos fell from the tree of beauty didn’t they?  I like those large head scales which give the snake a regal countenance.  That salmon blush that paints the chin and throat of males. Those large dorsal scales are soft and will dimple when gently pressed.  Indigos look you in the eye, a bit of a calculating intelligence there, seemingly. They don’t bite us either, as if they recognize this as a fool’s errand not worthy of their investment.

    Size and trophic status (adults are near the top of the food chain) separate Drymarchon from the rest of our serpent fauna.  These are definitely the bullies of the playground—all of our other local snake species are potential snacks for these snakes.  (There’s one heck of a difference between a five foot rat snake and a seven foot indigo snake, the former fitting comfortably in the belly of the latter). 

    Eastern diamondback rattlers up to 3-4 feet are commonly eaten.  Diamondbacks are scared you-know-what-less of indigos —those we have offered as prey to captive indigos freak out and hide their heads under body coils and body bridge, as if they know the specter of doom has arrived.  

How about an interesting fact about Indigos?

    All four of the Drymarchon species, including our Eastern Indigo, are essentially tropical snakes.  Here in the U.S. indigos, indigo are very much Floridian, a characteristic member of the subtropical (Florida) biota that extends a bit farther north into southern Georgia and Alabama.  

    Habitats in neotropical regions where our tropical indigos occur may support stunningly high species diversity of snakes and anurans (among other items sought by foraging indigos). And, when you crunch the numbers for Florida/Georgia/Alabama, you will be impressed to learn that at most sites where they occur, indigos share Deep South landscapes with ca. two dozen species of frogs and toads and up to three dozen species of snakes. 


I traveled about five hours southwest from the plains of Auburn, Alabama, to reach the Altamaha River, the heart of south Georgia indigo country.  South Georgia is a gently undulating landscape, essentially a patchwork of agricultural fields and pine plantations.  In the late afternoon, the mature cotton burns white in the fading sun. Deer hunters dressed in camos and carrying rifles and tree stands walk singly or in pairs down faint trails; the trails pass through manicured rows of planted pines and lead downslope to swampy bottoms  where yellow and orange leaves of poplars and gums supply some autumn color (about the best you’ll get around here).  Interestingly, the peak of the rut for the white-tailed deer coincides precisely with the time when indigo snakes begin breeding in earnest.

The next morning our party of four (Dirk, author and University of Florida professor Padgett Powell, herp enthusiast and Orianne Society member Lizzie Paulus, and myself) enjoy an ample herper’s breakfast of sausage, eggs,and  grapefruit before traveling to an extensive sand ridge to survey an indigo snake site that is among those populations that Dirk and Orianne monitor long-term.  First, we cross the roiling mass of a large brownwater river, then a smaller blackwater river; the roads become increasing sandy and narrow, and just before we park we cross a small tea-colored brook fringed with creek swamp (from Dirk “we’ve seen spotted turtles here, observed the same female basking on that stump the last 3 year”).

Ten minutes into our survey we find suspicious prints on the sand about the mouth of a gopher tortoise burrow that suggest a big snake is close.  Instantly, the air is charged with energy.

Guys, watch your step, watch your step!  Look close, oh man, this snake may be up right now.”  

The “watch your steps” cautionary warnings come from Dirk because large snake tracks at tortoise burrows at this time of year, are invariably made by one of two species (an eastern indigo or eastern diamondback rattlesnake).   One can sometimes find a large adult indigo snake at a tortoise burrow, then walk 50 feet to another burrow and encounter a fat diamondback (both have a penchant for overwintering in tortoise burrows in xeric sandhill habitats).  “Dave, we had an enormous rattlesnake here a year ago, up ahead along that berm, a genuine bunny-swiller.  A snake to sell snake boots.” He was kidding, of course.

Taking care not to kneel on spiky cactus pads that ring the mouth of the turtle’s home, we noodle the tubing of Dirk’s tortoise burrow camera deep into the bowels of the burrow; this allows us to view the nether-regions of the burrow on a small television that we rest on the burrow apron.  Over fifteen feet of camera hose has disappeared into the burrow before the nodding tortoise occupant becomes visible, seconds later blue pentagonal scales fill the color monitor.  

    It’s an indigo!

When we return two hours later we spot a new track indicating the indigo has crawled from the tortoise burrow.  A frenzied search ensues, without result.  Dirk comments, “It’s that time, you know. He’s hunting today, maybe a meal for energy, or hunting honeys”.  (We assume that this snake is a “he” because adult males, seeking courtship, are much more surface active this time of year).  A year ago Dirk and colleagues filmed indigo combat (fighting between rival males) at this site; after one bruiser of a bull evicted another hefty lunker from a burrow, they scoped the tunnel to find a third indigo (a female, later captured) curled in the bottom.  That afternoon we continue our search, visiting hundreds of tortoise burrows.  We find two indigo snake shed skins, including one just sloughed by a large (ca. six foot) female. Dirk points at a burrow that, “has indigo snakes in it every winter, without fail”.


Later that day we visit a second monitoring site.  Indigo habitat isn’t quite what I expected.  We visit a surreal moon-scape environment—an ancient dune of sugar sand with stunted vegetation.  Twisted sand live oak—their evergreen leaves an appealing rich forest green—and wizened examples of a tree-sized blueberry species are widely dispersed over the nutrient-poor sands.  It is easy to spot the large margarine-colored spoils of tortoise burrow aprons.  A decades-old dog pen, its planks faded and grown-over with mustard-colored lichens, is situated at the intersections of two narrow sand roads. “Dave, if you don’t behave or find any good snakes we may house you in the pen tonight”

“The nice indigo we got here last month pooped a rattler”.  Dirk is referring to a seven foot male that was spotted as it rested in a neat coil on the sand a few feet from a tortoise burrow; its feces (delivered during processing) contained snake remains and some mammal fur, the snake scales later identified as belonging to a young eastern diamondback.  I learn that tiny thumbnail-sized, straw-colored carapace scutes of hatchling gopher tortoises are commonly seen in indigo scats.  A bit ironic given the indigo’s dependence on tortoise burrows.

What is remarkable about the relationship between eastern indigo snakes and gopher tortoises ?

    The deep, thermally-stable burrows have been around long enough allow a number of wildlife species to evolve lifestyles that include habitual or even obligatory use of the burrows.  Did you know that an old colloquial name for the indigo is “Gopher Snake”?   We also have a gopher mouse, a gopher frog, gopher cricket, gopher tick.  There are number of invertebrate species found nowhere else on the globe except inside gopher tortoise burrows.

    Anywhere north of Gainesville, Florida, the indigo may accurately be regarded as an obligate commensal  (at least seasonally) of the tortoise burrow—from November through March, meaning the snake absolutely depends on tortoise burrows for shelter.  Actually, wherever the species (indigo and gopher) co-occur, as far south as Lake Okeechobee, indigos spend a whole lot of time in and around the burrows. Indigos are known to den (i.e., shelter), forage, shed their skins, lay their eggs, seek refuge from fire and predators, as well as fight and mate in tortoise burrows. 

    Our studies in south Georgia have documented that sites where indigo snakes thrive and persist today are invariably very large landscapes (5,000 – 20,000 ac of contiguous habitat) that include enough xeric sandhill habitat to support very large gopher tortoise populations (many hundreds to thousands of adult tortoises are present at most sites where indigos occur).

What have you learned from your mark-recapture studies of eastern indigo snakes in Georgia ?

    When we started marking indigos in 1999, one field on our datasheet asked for “Name of Snake”.  Obviously, we did so a bit tongue-in-cheek.  As scientists, we can’t defend naming our charges, but when you recapture snakes many times over an extended period (up to 5-8 years post-initial mark for some of our blue-black charges) you feel as if you know them.   I knew I could count on finding female snake “Foxy Girl” at least once a winter in the burrow complex along the powerline. An annual sighting of a massive nine-pound male “Lover”, even after his aging eyes became clouded with cataracts, was always anticipated close to one of the turtle burrows under the majestic longleaf pines comprising a particular red-cockaded woodpecker cluster (He returned there every winter to court, then guard burrows holding females).

    To answer your question:  from our mark-recap work we determined that eastern indigo snakes in southern Georgia: a) display sexual size dimorphism (SSD) with mature males (6.5 – 8 ft., 4-12 lbs.) being significantly longer and heavier than females (5 – 6 ft., 2-6 lbs.); b) snakes possess, as first reported by Auburn University professor Dr. Dan Speake, a genuine homing instinct and exhibit site fidelity by returning to the same tortoise burrow colonies, even using the very same tortoise burrows, in successive years.  This despite migrating from overwintering areas to foraging habitats located up to 1-4 miles away; c) indigo snakes may reach ages of 8-12 years in the wild, but seldom live longer.

The following morning we again cross the great muddy river fringed by an immense and Amazonesque  floodplain forest (Altamaha), but this time we travel south to a different survey site.  It’s a red-letter snake weather, sun glowing after a cool night, and we are optimistic.  Again, we have a snake within a few minutes of searching, but it isn’t an indigo.

As Lizzie climbs an old and nasty— one might say snaky-looking— blackberry-and-vine-covered berm, what looks like a scaly cable of gold slowly retracts into the shadows of a burrow.  “Diamondback, pretty one!”  We bend and crane, pull out mirrors and flashlights, in an effort to glimpse the massive but decidedly shy viper. The reptile seems to move backwards as it continues its retreat into the safe confines of an old gopher hole. A brief buzzing comes from the tunnel depths.

At our next stop, Dirk points as he directs us to a tortoise burrow complex which historically has been a guaranteed hot spot for indigos.  “Most of the burrows are within 200 yards of the road, on the south side.  Go as far as that large remnant longleaf”, he says.  “Most were well marked with flags and stakes when the site was thinned two years ago, you will still see some tattered flagging”.  As I later learn is his convention (from a conversation with an Orianne colleague who likes to bust his chops), Dirk immediately heads in the opposite direction, to yet another indigo honey-spot, the location of which he isn’t sharing.

Although we get skunked, he returns with a smile, wearing the newly cast shed of a 6 foot male indigo around his neck like a lei. Shed skins can be sexed by the presence of weak partial keels present on the mid-dorsal scale rows of male snakes.  We reconnoiter the area and determine the very burrow the snake is in, but the snake is lying low, staying in today (it’s very possible he’s in there courting a female as we speak”).

Could you revisit some of your early memories of indigo snakes?

    In the early 1990s, I ran drift fence traps for the Florida Fish and Wildlife Conservation Commission.  I worked for Kevin Enge, a pioneer in herpetofaunal surveys using drift fences.  We inventoried the herp faunas of several large properties and had 42 drift fence arrays with pitfall and funnel traps running simultaneously.  By the end of the year, I had odd sores on my shins which I attribute to daily wades through quiet waters well-stocked with wild pig feces.

    Walking a fair spit to a drift fence that we installed in a cabbage palm-live oak hammock, I would hike along an old healed-over firebreak through pond pine flatwoods that ran along the margin of an open and scenic sawgrass marsh.   I remember the fat, fire-scarred saw palmetto stems that snaked along the ground and the gnarly trunks of pond pines.  Pigmy rattlers were constantly underfoot.

    I walked up on several very large indigos here— intriguingly, the snakes I observed all seemed to perambulate slowly, at their leisure you might say, across this path.  The first few times I encountered such big indigos I invariably screamed (loud and repeatedly) to call my field companions.  If I was alone I still screamed.   Looking back now, I recognize that this site supported large numbers of snakes and rodents and turtles, making it good indigo country.

    Those wonderful cabbage palm–mesic flatwoods complexes near and north of Chassahowitzka along the Gulf Coast still have the indigos, although a historic decline for the Gulf Hammock region in Levy County was recently published. 

    Looking back, I guess I saw my first-ever genuinely huge indigo on a state highway south of Immokalee, close to Big Cypress.  Close to 7 ½ feet and 10 lbs., a true “monster male”. The indigo had just been creamed by a truck, and flashed purple-blue in the sun as it writhed, dying, in my trembling hands.  Of course this still happens all the time, although I doubt many folks realize it… We have an Orianne Society member, a teenager with a growing interest in herps who lives in rural south Georgia; her only two indigo snake observations have been DOR’s (dead on road)…  Very sad.  Broke her heart.  Indigos getting road-hit is and will continue to be, in the Anthropocene Era that is, a by-product  of their especially large home ranges and migratory character–they very often move considerable distances between habitat types 
(uplands to wetlands, etc.). 
Road mortality is not only a huge issue
for Indigo Snakes, but also many other species

Do you have a hero in the field of indigo snake study, besides me?

    I idolize the late Archie Carr and love Archie’s writing when it comes to indigos.  He describes indigos as “gun metal blue” and he remarks with awe on the tremendous size reached by specimens in the Everglades region.  In A Naturalist in Florida, Archie shares a remarkable story about a large captive adult indigo that had free roam of a young couple’s home.  The indigo would emerge from its lair behind a piece of furniture in the living room to watch—with head raised and seeming profound interest—whenever the woman breastfed her newborn child.

    Archie got it, you know. He understood what “conservation” meant before it was even a discipline, per se.  He was crushed by the loss of wild Florida.

Just where have eastern indigos experienced population declines ? 

    I attach a map from our status paper that shows regions from where indigos have gone missing, or at least are now extremely rare and possibly in an extinction vortex.  The amount of its historic range that the species no longer inhabits is spine-chilling.  

Courtesy Javan Bauder
    Note:  the indigo is now absent from Sanibel Island, off the Gulf Coast of Florida; a major roadway here (that has ridiculous daily traffic volumes) spliced directly through an upland/wetland interface, fracturing the snake’s primary dispersal corridor.  Ironically, the last indigo seen on Sanibel Island (in 1999) was run over and killed by a cyclist on a bike-path called “Indigo Trail”.

    The indigo is darn near gone from what was a marvelous subtropical and snaky landscape, the Florida Keys.  The culprit here thought to be roads, development and habitat fragmentation. Indigos were once common on Key Largo; now we have Burmese pythons instead.  By the way, just what effect pythons are having on indigos in the Everglades including Everglades National Park is unknown.

    We suspect that, historically, indigo snake numbers in Alabama and Mississippi were very small, as the range of the snake barely extends into these states.  As for the Gulf Coast region, the disappearance of the indigo from the Florida panhandle is both disturbing and intriguing.  Large expanses of sandhill soils cover much of the panhandle, and it’s likely that indigos (and gopher tortoises) were common here at one time.  However, this region experienced a dramatic decline (bordering on extirpation) in tortoise numbers—beginning ca. 100 years ago and caused in large part from overharvest by humans for food. Indigos seemed to disappear concomitant with the tortoise decline.  A large (500,000 ac) well-managed hotspot of biodiversity (Eglin Air Force Base) may still support a small indigo population, but there are very few recent sightings for the base and vicinity.

We return to the first ridge, the one where we saw the rattler earlier this morning.  “There will be snakes out now”, Dirk reassures us, knowing that we all hope to make the long drive home smelling of indigo musk — a musk of singular pungence and renowned for its ridiculous staying power, Dirk informs us.  (It’s almost a certainty that any captured indigo we “work up” [sex, weigh, measure, mark uniquely with a PIT-tag, and photograph]  will respond to these proceedings with some heavy hissy breathing, a lively tattoo  of its tail, and by issuing some pinkish paste from its cloaca. 


Both of Padgett forearms are bloody, when he dove for the indigo blackberry thorns fanged him, leaving incisions comparable to small furrows from which now run and drip rivulets of dark red blood.   

Breathing deep with adrenaline, shirt open to reveal sweaty chest hair, acclaimed author Padgett is for now speechless.   Then, a wonderfully creative string of expletives documents that our man of letters is ok, still capable of speech, albeit stung by his inability to grab the fleeing indigo.

Padgett estimates the snake at 6 ½ feet.  They spotted each other about the same time.

Padgett: “He looked at me. He was stretched out as if going somewhere (but he wasn’t moving.) His head was up off the floor when I spotted him…. And he was looking at me. Then he ran like hell, straight for that burrow… I might’ve flinched when I hit the berries, would you look at those thick-^%$ blackberries! I felt my fingertips glance the scales of his tail.”  As he tells us this, Padgett ponders his hand, the one that touched the indigo. 

Given the dimensions and density of the blackberry thicket which guarded and protected this snakes retreat,  considering that indigos are visually-skilled and can see danger coming, it’s a wonder that Padgett was able to come as close as he did to capturing the indigo. 

We check on the rattlesnake again, and we do the right thing, deciding against trying to hook it from the burrow for photos.  Let’s leave the rattler alone. Our two day tally comes to nine miles perambulated (per Lizzie’s FitBit) and 260 tortoise burrows inspected (per Dirk’s guesswork)—to the tune of two indigos, four indigo sheds, and the diamondback.  But, we are all a bit frustrated and energized by Padgetts near-miss, and hungry to look more.  Dirk chimes in, “Actually, we average about 1 indigo per day, so we didn’t do bad.  But, I do wish y’all would’ve had the opportunity to work some up… Yeah, its addictive allright.  Walking around these quiet sandhills for hours seeing nothing but sand and then looking down to see a seven foot indigo or a gorgeous jingle-tail.”

As we shake hands I take a long look at the sand ridge, so that I can remember this.  I hope to get back and chase indigos again soon.

Can we save the indigo snake?

    Dave, this is a great question, and a hard question.   We sure hope so…

    By 2060—per habitat models based on projected land use patterns in Florida—indigo snake populations in the Gator state will be mostly restricted to large islands of protected habitat (awash in seas of developed or otherwise unsuitable landscapes).   Meanwhile, in Georgia, although the snake is doing well locally in a few regions, some of the best indigo habitat in the state is now privately-owned (e.g., hunt clubs); obviously, these properties have no long-term security and many are not being appropriately managed (e.g., regular prescribed fire programs in place) at this time for snakes and tortoises.  Most herpetologists do not expect the snake to get much commoner in the future, nor do they anticipate that the species will ever be “recovered” (that is delisted).      

How about some good news?

    The ongoing, determined efforts by Auburn University personnel, The Orianne Society, and a number of other important partners (Central Florida Zoo, AL DCNR, FFWCC, GA DNR, TNC, US FWS, Zoo Atlanta) to re-establish the indigo in the western part of its range could ultimately go a long way toward ensuring the species long-term survival.   

    The last 15 years have seen a dramatic increase in funding dedicated to indigo snake and gopher tortoise field studies and conservation (this has helped increase our knowledge of these critters as well as save habitat).  The states within the current (extant) range of the snake (Georgia, Florida) as well as Alabama have expended enormous time and resources to locate, map, inventory and prioritize acquisition efforts for sandhill habitats that support indigos and tortoises.  

    Thorough gopher tortoise surveys are now being regularly conducted throughout the turtle’s range.   Burn programs and longleaf pine restoration efforts as they relate to nongame wildlife species are getting better and gaining recognition.

    Those in our field walk in acknowledging the challenges are great and in some cases insurmountable but we are in this to affect change and to promote conservation and we are determined to make a difference.   I am very fortunate to be able to work with not just the indigo snake but with so many dedicated and intelligent people who want to protect this snake and its ecosystem.  We are very fortunate that the generous donations of philanthropists passionate about indigo snake conservation allowed The Orianne Society to focus on programs that bring attention to this iconic reptile. 

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