Posts Tagged ‘wrack line’

For Some Hatchling, Nursery Lies in the Uplands

Thursday, September 11th, 2008
 
One surprise we discovered over the last few years is that diamondback terrapin hatchlings employ a variety of strategies to survive their most vulnerable first year.  We had all expected that like sea turtles, terrapin hatchlings scramble from their nests in a beeline for the safety of the thick, rich, robust nursery salt marsh habitat ringing Wellfleet’s most productive nesting sites.  The first indications that we may have been hasty in this assumption were hatchlings we found in May and June each year heading DOWN HILL from the uplands toward the salt marsh.  The first few observations were dismissed as late emerging hatchlings that had overwintered in their natal nests since we had documented a few nests in May and June that had hatched in the fall, but where some hatchlings had remained until the next spring.  However, once we spotted yearlings heading down slope from the uplands to the marsh this rationalization collapsed.
 
Dr. Barbara Brennessel of Wheaton College conducted experiments tracking headstarted hatchlings released in their natal habitat in the Wellfleet Bay system.  They were equipped with a transmitter for RDF (radio direction finding) tracking.  Although much larger than a normal hatchling due to overwinter feeding, a number of these turtles headed into the salt marsh, behaving precisely as we would have expected a baby terrapin to act.  They hid out in the thick Spartina patens, feeding on whatever small critters they could discover in this rich marsh system.  However, some number of these headstarts went upland into the vegetated banks abutting sandy nesting areas and the salt marsh.  Since these animals were not “pristine” hatchlings, we asterisked their “aberrant behavior.”
 
But once we began to track baby hatchlings emerging from natural nests on treks upland, we realized that putting all the data together, many hatchlings race into the robust Spartina patens of the Wellfleet salt marsh system, lots of hatchlings dash under the rimming wrack line between sandy nesting banks and the salt marsh, and still others scale the banks and dunes to explore the vegetative uplands above the most productive nesting sites.  These terrapins employ a richer, more complex strategy that offers multiple opportunities for survival of hatchlings in a very raw and unpredictable climate at the northernmost edge of their range.
 
This week we watched the emergence of a nest at Turtle Point.  Ten live hatchlings left the nest and we followed them with a long-distance telephoto lens to determine how this group might behave once they had tunneled out of the nest.  You may recall earlier reporting of tracking hatchlings into the wrack line and others into the Spartina patens (see Tracking Terrapin Hatchlings, http://www.turtlejournal.com/?p=225)
 
The first hatchling set out on a solo trek and headed immediately into the vegetation above the nesting bank.
 
 
Solo Hatchlings Climbs into Upland Vegetation
 
Three others seemed to wait for this scout to complete its scramble, and then they too scaled the bank to disappear into upland vegetation. 

Three More Hatchlings Scramble Upslope

The last batch of six hatchlings followed suit, with the final two in this pair offering quite a tag team performance.
 
 
Final Six Head Upland, Too
 
Finally, once they had fully dispersed into the uplands, we attempted to find them again.  Truth be told, even though we had followed their movements in detail with a long distance telephoto lens, we could only locate four of the ten hatchlings because they were so well camouflaged within the groundcover vegetation.
 
 
Hatchlings Camouflaged in Upland Bearberry Vegetation
 

Tracking Terrapin Hatchlings

Friday, September 5th, 2008

Where do hatchlings go once they flee the nest? Using various methods of inference and observation, we have determined that some hatchlings race to the wrack line for safety, others scramble further into the salt marsh grasses and still others opt to remain upland for at least the first winter of their “hidden” years.

Terrapin Hatchling Track Heads Down Turtle Pass Dune

Let’s follow some clues, some tracks and some hatchlings to test these hypotheses.  The high dune of Turtle Pass seems the place to start as we discover a hatchling track descending from an emergence nest atop the dune and heading seaward.

Tracks Assume Colorful Tints as Sun Dances Behind Clouds

Down we go along the shifting slope that morphs in shape and color as shadows dance through the contours of the dune.

Close-Up with Tail Mark Bisecting Track

Let’s experience the descent as though we were a newborn hatchling on its first ski run down the slopes.

Follow Tracks to Hatchling Buried in Salt Marsh Wrack

So, our first experiment leads to the discovery of a hatchling burrowed into the landward edge of the wrack line, buried under last winter’s deposit of salt hay.

But our day isn’t over as we encounter another set of hatchlings scaling the bearberry covered banks off 5th Avenue and passing through an exquisite clump of sea lavender en route to safety.

Terrapin Hatchling Scrambles to Reach Salt Marsh

These little critters eschew the wrack line, which to them seems like a clear cut jungle of logs, and head directly into the thick matting of Spartina patens in the salt marsh system separating east and west sections of Lieutenant Island.

Landslide!

Wednesday, September 3rd, 2008

You’ve just been born; you discard your eggshell and tunnel to the surface. Now you must make a mad dash for safety. Unlike sea turtles who hatch at night and head for the brightest horizon (hopefully the sea, but all too often a local fast food restaurant), you emerge during the day and head out in a random “drunkard’s walk” without any clear sense of direction, hoping to find vegetative shelter. Momma lays her nest on a steep slope, hoping you’ll take the hint and slide downward into the safety of wrack line and salt marsh grasses. But you choose the “high road,” struggling like a Mount Everest sherpa to climb the soft, sandy, high dune of Turtle Point. And then comes the landslide.

Confronting Sandy Avalanche with Neither Angst Nor Doubt