August 20, 2016

As naturalists, what we observe and learn is directly connected to how we look.  I spent more than a decade involved in field and laboratory studies of dusky pigmy rattlesnakes (Sistrurus miliarius barbouri), during which time I had the great fortune to observe thousands of these charming little pit vipers in both natural and captive environments.   Still, during all that time studying pigmies, I never witnessed a behavior I was able to watch yesterday morning while road-cruising the forest roads of Ocala National Forest.

Most of my field observations of pigmies in years past took place during systematic group censuses of our primary study population.   A group of dedicated snake searchers moved slowly through the hammock habitat, looking for the sometimes abundant pigmies, most of which were individually marked as part of a long-term mark-recapture study.  The premium was on finding as many snakes as possible during the census, and measuring characteristics of the found snakes, such as location, substrate, length, weight, and so on.  The upside of this approach is you get to see a lot of snakes.   The downside is that you don’t get to watch individual snakes very long before you’re on to the next one.

Not that watching individual snakes is a very productive use of time, in general.   Pigmy rattlesnakes normally don’t do much most of the time.  They are classic ambush predators, and will sometimes remain in a foraging coil without moving for days at a time.   The majority of snakes found are coiled and waiting for some unsuspecting frog or lizard to foolishly venture within striking range.    The frequency of pigmy rattlesnake movement varies seasonally; in winter and summer months, only 5-10% of snakes found are moving (May et al., 1996).   The remaining 90-95% are in foraging coils.  The proportion of moving snakes rises to as high as 15% in spring and fall, but at any time of year, most of the snakes that are out and about (as opposed to sheltering under cover) are immobile.    So watching a foraging pigmy rattlesnake is, for the most part, a lot like watching paint dry.   Observing the snakes that were moving when first seen isn’t much more productive; they are nearly always aware of the human observer’s presence, and when they resume movement, their goal is mostly to get to cover and out of sight.

Yesterday morning began not long after sunrise, as I started the first day of data collection for my sabbatical research.  The focus of this study is bird behavior, and in particular the effectiveness of different auditory cues in eliciting mobbing responses of passerine birds.   Snakes were not the furthest thing from my mind (they rarely are), but I wasn’t thinking as much about snakes as I was about birds.  A couple of hours of playback trials occupied me for the early part of the morning, and produced a few cool birds – lots of northern parulas, several prairie and yellow-throated warblers, a couple of FOS ovenbirds, and at least a half-dozen summer tanagers.  In addition to the neotropical migrants, year-round residents were in evidence everywhere – lots of Florida scrub jays, including many scruffy gray-headed youngsters, tons of towhees, and frequently heard, infrequently seen white-eyed vireos.  By 9:45 or so it was hot enough that bird activity was on the wane, so I gave up the structured protocol of research and switched to random road-cruising fun.

A couple of distant, rapidly moving black racers were the only snakes I found crossing Forest Road 33; at about 10:30 I headed east on FR 46 towards its intersection with SR19, and then home.  It was warm enough I didn’t expect to see much bird or other wildlife activity, but I was ready to be pleasantly surprised.  I saw a bear on this road around mid-day last fall, so anything is possible.

I slowed a bit at the Pat’s Island Trailhead parking lot, and when I did so, I saw a lizard dart from the soft sand at the road’s edge towards cover.  He stopped briefly in the open, and I maneuvered my big lens into position to scan the ground for the saurian.  I found him, briefly, before he retreated fully into cover and out of sight.  It was a male scrub lizard (Sceloporus woodi), a Florida endemic that, though locally abundant, always gets me a little hyped when I get the chance to photograph one.   Which this guy refused to give me.   But while scanning the ground for the cryptic scelop, I saw something else I would have completely missed with a naked eye view – a neonate pigmy rattlesnake stretched out on the sand and debris.  The small size and bright yellow tail identified it as a YOY – a young-of-the-year snake that was almost certainly less than a month old, perhaps no more than a few days old.  It still had only the original button that rattlesnakes are born with, meaning it had shed its skin only once (the post-natal shed, which comes 2-4 days after birth and leaves the snake with a single rattle segment).  His second shed would add the first interlocking rattle segment below the button, and and would allow this snake to actually rattle, sort of, if it chose to.  Which they rarely do.   Pigmy rattlesnakes are kind of an embarrassment to the whole notion of rattling.

As is typical of pigmies that are detected by a big stinking primate while they are moving, this one had frozen into complete immobility.   Such snakes are acutely aware of the sweaty mammal, and usually will remain static and somewhat cryptic for a minute or three; at some point, they apparently decide (?) that the threat is diminished and gone, and they slowly crawl to cover.   But this one didn’t do that.

Instead, it began poking its head around the palm frond debris nearby, tongue-flicking occasionally.  After a couple of minutes of exploratory behavior, he slowly formed his body into a foraging coil.  This process took several minutes, and was completed as the little snake rocked his body back and forth a few times to settle down into the sand.  It was of interest to me that when the coil was complete, the yellow-tipped tail wasn’t particularly prominent.   Young pigmy rattlesnakes sometimes use their brightly colored tail tip to mimic a small caterpillar or insect larva, wiggling it when frogs or lizards are nearby to entice them into taking a bite.  If all works according to plan, the pigmy then takes his bite.  The behavior is called caudal luring; the baby pigmy I was watching wasn’t doing it.

So at this point I figured the excitement (!) was over.  The baby pig was settled into its foraging coil, and might not move for hours or days.  Still I hung around and watched.  I was hoping the scrub lizard might make a reappearance, but didn’t really expect any other action from the pigmy.  Still, I was pretty happy with what I’d seen so far.  In all the years of watching pigmy rattlesnakes in the field, I had never observed one actually form a foraging coil while I watched.   The tongue-flicking prior to coiling suggest that chemical cues may be an important part of site selection.  Eric Roth showed over a decade ago while working on the pigmy research project that pigmies are more likely to coil and hunt in areas that have been sprayed with frog scent than in nearby similar areas lacking frog odors (Roth et al., 1999).

I was quite surprised when the little viper began moving his head back and forth a bit, and tongue-flicking.  He had been in his coil for less than 5 minutes.  When he initially coiled, the spot was in shade, but a moving sun fleck was beginning to encroach on his foraging site.   That particular foraging spot would be completely untenable if exposed to full mid-morning sun; the little pigmy would be overheated within minutes.

So the little dude did a very reasonable thing – he switched spots.  But not very far.  He slowly crawled to a still shaded spot less than a foot away, and repeated the behavior.  He began nosing at and tongue-flicking around a small twig, and soon settled into a foraging coil situated partially under the stick.  The process of forming a coil was much quicker this time.  Time stamps from the series of photographs I took reveal that it took him several minutes to form the first coil, but only a little over a minute for the latter.He was still in his second coil when I drove away, but I doubt he stayed there long either. The entire area was soon to be exposed to direct full sun, which would surely require that he relocate again.

Was this baby snake learning how to choose a foraging site?   Snakes as a group have never been considered by most biologists to be particularly “intelligent”, whatever that term means.   The general view of comparative intelligence among the vertebrates has long been that while birds and mammals are highly intelligent and capable of complex cognitive feats (“learning animals”), the ectothermic vertebrates (fish, amphibians, reptiles) are primarily “reflex animals”, relying mostly on hard-wired, fixed behaviors to respond to environmental challenges.  My personal view is that we probably underestimate the cognitive capabilities of most animals.   There’s shit going on there we have very limited means of studying and understanding.

From a purely practical standpoint, it seems reasonable that young pigmy rattlesnakes should learn how to choose better foraging sites as they get older.  A successful foraging site, particularly one that results in capture and consumption of a prey item, should provide positive reinforcement regarding the characteristics of that foraging site, and the site-selection behavior of that individual should be modified.   Actually demonstrating learning by individual animals is a tough nut, though, especially in the field.  For learning to have occurred, the snake would have to modify some aspect of its site selection behavior as a result of earlier experiences.

Demonstrating learning in non-human animals requires controlled conditions and laboratory studies.   A quick and dirty Google Scholar search for primary literature on learning in snakes turns up only a handful of citations, some of which show limited modification of behavior based on experience, and others that don’t.  Garter snake babies become better at following worm trails with experience, but Richard Shine and his colleagues have shown that Australian black snakes (Pseudechis porphyriacus) don’t learn to avoid toxic cane toads (a novel, non-native prey for these snakes) after encountering them.  However, populations exposed to the toads rapidly evolved behavioral avoidance of cane toads, compared to populations with no previous exposure to the toads (Phillips and Shine, 2006).  The naïve snakes readily consumed the toads, much to their detriment. This result suggests that toad avoidance in these snakes is an evolved, genetically based behavior.

It would be an extremely premature and foolhardy conclusion to state with any confidence that I had observed a snake learning. None the less, I’m pretty sure that’s what I did.

 

 

References

May, P.G., Farrell, T.M., Heulett, S.T., Pilgrim, M.A., Bishop, L.A., Spence, D.J., Rabatsky, A.M., Campbell, M.G., Aycrigg, A.D. and Richardson, W.E., (1996). Seasonal abundance and activity of a rattlesnake (Sistrurus miliarius barbouri) in central Florida. Copeia, pp.389-401.

Roth, E., May, P., & Farrell, T. (1999). Pigmy Rattlesnakes Use Frog-Derived Chemical Cues to Select Foraging Sites. Copeia, 1999(3), 772-774.

Phillips, B. L., & Shine, R. (2006). An invasive species induces rapid adaptive change in a native predator: cane toads and black snakes in Australia.Proceedings of the Royal Society of London B: Biological Sciences,273(1593), 1545-1550.

 

 

Title credit: E. Eugene Spears

January 12, 2014

My buddies for life (I think) Skeate and Spears made their annual trek from the hellish cold of Banner Elk,  North Carolina to pay me a visit this week.   The three of us met as grad students in the fabled zoology department at UF back in the 80s, and they have been my closest friends since.  All of us were Florida newbies, and we learned about community ecology and the terrestrial ecosystems of peninsular Florida from the same mentors at around the same time.   Nonetheless, it was a major rush for me to spend a couple of days sharing my recently ignited passion for Ocala National Forest and its diversity of plant communities and landscapes with them by visiting a couple of my favorite spots in the forest.   We had all taken Community Ecology at UF with field trips led by the great man, Dr. Archie Carr, whose knowledge and understanding of Florida natural history and ecology were nothing short of miraculous.  So by comparison, my puny attempts to enlighten them somewhat about the scrub, high pine, and associated habitats were kind of laughable.  But all we can do is take what we’re given, G.  We had no particular target taxa in mind; we were just road-cruising, happy as scallops for whatever natural history nuggets we might chance upon.

In fact, this post might be better called the anti-snipe hunt, as it is antithetical in nearly every respect to the traditional snipe hunt.  In a regular snipe hunt, a naïve nimrod is stationed somewhere in purportedly suitable habitat, preferably on a dark, moonless night, to wait for the mythical snipe to appear and bag it.  It’s a very focused pursuit, but typically produces no useful outcome other than amusement for the instigators.  By contrast, we were three unfocused but somewhat knowledgeable fellows, looking for nothing in particular, nearly constantly in motion, covering a lot of territory on a bright morning.   And our efforts produced several useful outcomes, including crippling views of the legendary snipe.  No capture other than digital, though.

On Friday, we first visited a tract of private property a bit south of Astor Park that included the remains of some old sand-mining operation, and then we headed southwest towards the Alexander Spring section of the forest.   As we tooled southeast on FR18 towards the 52 Landing boat ramp on Alexander Springs Creek, we saw (incredibly briefly) a 3-4’ snake speed across the road and into the cover along the margin.   Perhaps as quickly as I’ve ever seen a snake cross a 20’ wide roadbed.   I didn’t even get a look at the head before it disappeared out of sight, but the sand-colored caudal half of the body and rapid rate of transit was enough to identify it:  coachwhip.   As we savored the buzz of the sighting, we reminisced about the coachwhip we saw while on a Community Ecology field trip to the Ordway Preserve over 30 years ago.   Most of the dozen or so grad students in the class, and a couple of faculty, were in the departmental van ahead of me.  As I still am, I was a driving fool and so was following the van in my tortured old ’75 Ford Futura.   I had to slam on the brakes and skid to a sudden stop in the sugar sand ruts as the van ahead of me did the same; the side door opened and about a half-dozen people exploded out of it in pursuit of the coachwhip that had crossed the two-track we were driving on through the successional pasture.   Most of these herpetophiles were young men in their physical prime, but the great Dr. Carr, then somewhere in the neighborhood of 71 years old, beat them all to the beast and with a great flying leap pinned the coachwhip with his torso.

The nasty masty turned around, clamped down on Dr. Carr’s nose, and held on.  And Dr. Carr stayed chill, knowing that any movement might cause the snake to rake his not-insubstantial rows of sharp teeth through his rostral flesh.  After a few seconds, the coachwhip, still mostly immobilized by Dr. Carr’s weight pressing on him, let go of his nose and looked around.  One of the other members of the group immediately grabbed the snake a bit too far down the neck and pulled it from underneath Dr. Carr.   The coachwhip promptly latched onto his hand and raked, causing him to begin gushing blood from numerous small lacerations.  After they released the snake and it began its retreat from the band of stinking primates, I took two photographs of it as it periscoped and scanned its surroundings before boogying at top speed.  When I received and viewed the processed slides, I saw that a small turkey oak seedling beside the snake was speckled with blood.

We had no comparable adventure with the Ocala coachwhip yesterday; it was gone before the three of us had even processed our sensory input and identified the snake as a coachwhip.   Conclusion from this and countless other anecdotal evidence:  Dr. Archie Fairly Carr Jr. was a great, great man.

The rest of Friday’s trip, which included Paisley Road and FR06, was lovely but unproductive of anything other than stunningly beautiful habitats.   Our sampling of gorgeous and diverse habitats resumed on Saturday, when we took FR11 north from SR40, a bit west of Astor Park, and followed it to its end at Ocklawaha Lake, on the boundary of Ocala National Forest.   Unlike most forest roads, the stretch of FR11 between SR40 and its intersection with SR 316 just northwest of Lake Kerr is paved.  This section of FR11 passes mostly through scrub, though the range of scrub subtypes spans nearly the entire gamut, from recently harvested clearcuts to mature, even-aged stands of nearly pure sand pine, and all the intermediate successional stages connecting these two endpoints.

Once north of 316, as FR 11 approaches the Riverside Island tract, the road reverts to the more typical yellow sand. It was here that within a stretch of no more than a mile or two we spotted two different black bears poking around the road margins. We stopped and glassed both animals for a minute or two from a distance of a couple hundred yards, and they glanced up the road at us but remained unconcerned until I tried to drive closer to them, at which point they both slowly retreated back into the sand pine scrub.  It seems like there must be some meaning to the observation that in the 35 years I’ve lived in Florida, I’ve seen black bears in natural habitats (I’m not including the young bear I saw at 2 a.m. in the morning from about 5’ away destroying the bird feeder and pole just outside the window of my DeBary home, nor the one that wandered onto the Stetson campus one fall a few years back, climbed up into a smallish oak tree in front of the student union, and snoozed there for several hours as students and staff treated it like a rock star and gathered around to ooh and aah) maybe 11 times, and that eight of those sightings have been in the last 6 months.  But more likely it is just a reflection of the random and unpredictable nature of actually seeing uncommon and wary wildlife.

Further north on FR11 the habitat transitions from scrub into regenerating sandhills, and then a bit further on, mature tracts of longleaf savannah where I had several killer encounters with roving clans of red-cockaded woodpeckers last year.  The bright cloudy skies on this breezy morning provided the perfect diffuse lighting to accentuate the panoply of brown hues produced by the numerous conspicuous grasses.   Luscious golden browns of Andropogon, creamy tans  of wiregrass, a diverse range of intermediate tones from other grasses and senescent forbs – it’s a beautiful time of year to be in the sandhills.

At Rodman Dam, I was hoping for a variety of dabbling and diving ducks, but the only aquatic swimmers to be found were big flocks of American coots.  While watching a couple of killdeer exploring the broad grassy berm of the dam, I saw a lone Wilson’s snipe toddling slowly up the slope.   Confident that it would flush with a buzzy prrrrrt as soon as I got anywhere close to it, I idled towards it hoping to grab a shot or two.  And behaving exactly like a consummately cryptic bird should, it surprised me by never flushing, ultimately allowing me to drive within about 15 feet and fire away to my heart’s content.  It was still hunkered in the same spot as I slowly pulled away.

The friends I made in graduate school were some of the finest people I’ve ever been privileged to know, and those relationships seem to sweeten and intensify with time like a fine wine.   Can’t go back to those halcyon, treasured times, I know, but spending time with old friends like Skeate and Spears is maybe the next best thing.

The post-script to this story concerns stuff we didn’t see.  Before their visit, I was totally jazzed by the prospect of showing off the pair of painted buntings that had been visiting my gardens for the previous couple of weeks.  But both those birds disappeared about a week before my friends arrived, and despite my repeated entreaties to the bird gods, the male never returned while they were here.   Coco, the female, did put in brief appearances on Friday and Saturday afternoon, but the incomparably beautiful male waited until 3 hours or so after they pulled out this morning to make his return.   The serendipity of natural history.   Next year, my friends.