Saturday, January 07, 2012

I have developed a full-blown obsession with map turtles (Graptemys - the genus name translates into just that, map-turtle). This would not be a problem if I lived near lots of map turtles, say in the Florida panhandle (also known as Heaven) or better yet, Mississippi (six species) or Alabama (at least six). Up here in the Delaware Valley we should have zero species of map turtles, though we're lucky to enjoy a population of common/northern map turtles (G. geographica - again, what a neat scientific name!), native to PA's central and western rivers, but apparently introduced in the Delaware just above the fall line a hundred years ago or so. Since then they have spread up the river (common now in the Water Gap), down the river (showing up now and then at the Heinz NWR), and back up the Schuylkill at least as far as Valley Forge.

Now, I adore the common map turtles - see my snorkeling posts going back a couple years - but someone with a full blown obsession is not satisfied to enjoy the one variety of the object of his obsession that happens to be convenient. No, the obsession does not permit such easy satisfaction, it demands comprehensive commitment to maximization, and there are thirteen species of map turtles and two or three more subspecies, depending how you count them:

  • Northern map turtle: G. geographica, the one we've got up here. The carapace (top shell) is patterned with fine green and orange lines like roads and borders on a map. These guys inhabit the northeast quarter of the country, from Wisconsin over to Upstate New York and down to North Georgia.
  • False map turtle: G. pseudogeographica, a funny specific name if you look at it without reference to the geographica. What does it mean to be pseudo-geographic? You could count two subspecies, basically northern vs. southern sections of the Mississippi River system. The northern one is G. p. pseudogeographica, the southern G. p. kohni.
  • Black-knobbed map turtle: G. nigrinoda, a nicely descriptive name for a turtle with prominent black knobs running down its back. Along with the next two 'sawback' species, these have relatively small heads and have a relatively insect-oriented diet. They live mostly below the fall line in the rivers that flow into the Mobile Bay and share their waters with the Alabama map turtle. These have been traditionally divided into two subspecies, with the darker-colored turtles that live close to the Mobile Bay as G. n. delticola.
  • Yellow-blotched map turtle: G. flavimaculata, another descriptive title. These live in the Pascagoula system below the fall line, and share it with the Pascagoula map turtle.
  • Ringed map turtle: G. oculifera, a scientific name a little more evocative ('eyed' map turtle) than the common name. These live in the Pearl River system below the fall line, sharing their habitat with the Pearl River map turtle.
  • Barbour's map turtle: G. barbouri, a one of the broad-headed species; three of the four broad-headed species have boring, place or honorific names. It's nice to honor a great herpetologist like Barbour (and Ernst, and Gibbons), but why not something more descriptive or evocative, like 'Snail-Crushing' map turtle, or 'Beefy-Headed' map turtle? These four species have such freakishly enormous heads that it's a crime to ignore them in the species names. Barbour's map turtles live in the Chattahoochee/Apalachicola River system.
  • Escambia River map turtle: G. ernsti, in the Escambia River system.
  • Alabama map turtle: G. pulchra, which means 'beautiful,' a perplexing species name since they're pretty bland-looking map turtles. They live in the same rivers as the black-knobs, but range further up above the fall line, the same pattern that you see with the Pascagoula and Pearl River map turtles.
  • Pascagoula map turtle: G. gibbonsi
  • Pearl River map turtle: G. pearli, a species very recently split from G. gibbonsi based on genetic differences and very subtle pattern differences.
  • Ouachita map turtle: G. ouachitensis, a narrow-headed species that ranges through much of the Mississippi River system, from Louisiana to Wisconsin. The Sabine River map turtle (G. o. sabinensis) lives, guess where?
  • Texas map turtle: G. versa, of the Colorado River system in Texas. These guys have pretty orange spots on either side of their lower jaw.
  • Cagle's map turtle: G. caglei, of the Guadalupe River system in Texas, a species with an intricate pattern of fine green lines - very pretty.

I had a goal last spring, a goal that didn't seem as crazy at the time as it does right now, to find and catch if I could all eleven of the thirteen species that live in the Mississippi system and east. If you look at a map (the geographic-representational kind) it's a pretty simple task, right? You've got western Florida over to southern Louisiana and back up to Pennsylvania. The two species out in Texas might be another trip. The next few posts will be an account of my attempts to reach this goal.

Technique: Readers of this blog probably have noted by now my disdain for road cruising and my tolerance, at best, for driving around from trash-site to trash-site to flip critter. I like immersion herping: hiking up into mountains, slogging through swamps, and, most immersive of all, sinking down into rivers with mask and snorkel to find turtles. Readers also will recall my dear inflatable kayaks. Put it all together and you've got my turtling method: paddle or slog my way up or down rivers looking for juicy spots to jump in and snorkel.

Not just any spot on the river would work, however. First, the spot had to be accessible; a stretch of river might look great on the map, but if no roads or bridges cross it I can't get in it. Second, the water had to be clear enough for me to see turtles. This was often hard to discern, no matter how hard I tried to interpret the USGS water statistics (I've been spoiled by the very direct turbidity readings for the Delaware and the Schuylkill, absent for most Southern rivers), and a few times we (along with Scott) walked down to the bank of a turtle-rich river to find a torrent of brown or green water in which we couldn't make out our hands in front of our masks, let alone a turtle under a log on the bottom of the river. Third, and connected to the second point, the weather had to cooperate. Rain and the ensuing runoff washes silt (and manure, God knows what else) into the river and can turn a placid stream into a dangerous torrent. Last, and connected to the previous two points, I wanted a creek or river with a lot of forest in the immediate watershed. Rain washing off an over-grazed cow pasture or a crop field carries into the water far more soil than rain whose impact is buffered by tree canopy and then drips down to meet leaf litter and roots rather than bare soil.

Is this enough background? Stay tuned for the actual map turtling accounts, beginning with the next post.