Posts Tagged ‘survival’

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
 

Sad Tale of Three Dead Leatherback Sea Turtles

Monday, September 8th, 2008

Leviathans of the sea and giants of the reptile family, leatherback sea turtles define the term superlative.  Ranging in weight up to a ton and the size of a small Volkswagen, no one who has encountered one of these living relics in the wild comes away from the experience unchanged.  They are simply magnificent beasts that peacefully ply the world’s oceans in search of slurpy jellyfish.  The open mouth of a leatherback sea turtle (see below) is perfectly configured for this quest and is the last thing that a jellyfish senses before the lights go out.

Mouth of 650+ Pound Male Leatherback Sea Turtle

Unfortunately, we humans offer them a complex series of lethal obstacles to avoid during their peaceful voyages.  Gill nets drown them, longlines hook them, propellers slice them, weirs trap them and lobster buoys entangle them.  Especially during the summer months in Cape Cod and Buzzards Bays as they chase plentiful jellyfish, endangered leatherbacks face a host of potential threats.

Male Leatherback Arrives at Wellfleet Sanctuary for Necropsy

A freshly dead 650+ pound male leatherback beached in Provincetown on Sunday and Mass Audubon’s Bob Prescott, the state sea turtle stranding coordinator, conducted a necropsy at the Wellfleet Bay Wildlife Sanctuary to determine the cause of death and to gather scientific information to help us conserve this endangered species.  In addition to his staff, Bob (with large caliper below) was assisted by Kara Dodge, a PhD candidate at UNH and former NOAA sea turtle coordinator, and the Turtle Journal team.

Bob Prescott (Calipers), Don Lewis (Camera) and Kara Dodge (Scalpel)

Too large for normal scales, the mass of leatherbacks is determined by weighing the Mass Audubon pickup truck at the dump with the turtle inside, and then re-weighing the truck without the turtle.  The post revealed that this animal had been very healthy.  “It had everything going for it,” stated Bob and Kara.  Both flippers showed signs of a recent entanglement, but nothing so severe that these wounds would have caused death.  Instead, the cause of death was determined to be drowning.  The likely scenario for the death of such an inherently healthy animal is that it got entangled in a buoy line with both flippers wrapped in the rope and perhaps its body trunk as well.  With the last series of spring tides, the turtle may not have had sufficient line to reach the surface.  Like all turtles, leatherbacks are air breathers and will drown if held under water for a sustained period.  How this drowned animal had then become disentangled from the lines that had been wrapped tightly around its flippers is merely a matter of conjecture.

This evening we received a call from Bob Prescott that there had been a report of a dead leatherback on a Westport beach near Horseneck.  We drove out to the site and after about 30 minutes of searching, we discovered a badly decomposed and deflated leatherback sea turtle.  Talking to a local resident, we learned it had been bouncing along the beach for at least the last three days.  We estimated the carapace at approximately 161.3 centimeters, but decomposition and deflation may have altered any accurate rendering of its precise size.  Bones were exposed throughout from head to back to flippers.

Decomposed Leatherback Sea Turtle in Wesport, MA

Another decomposed, 600 pound leatherback washed ashore at Pico Beach in Mattapoisett Saturday night (http://www.southcoasttoday.com/apps/pbcs.dll/article?AID=/20080909/NEWS/809090352/-1/NEWS).  Dealing with one dead leatherback is serious as population numbers of this critically endangered species continue to plummet.  Finding two dead leatherback carcasses in a weekend is a tragedy; but three dead leatherbacks fall beyond emotions and words.  Yet, a ray of turtle hope winked through the afternoon when a call came into the Hotline.  A woman found a small 1/2 dollar size turtle in Plymouth, Massachusetts as kids were placing it in the ocean and the animal was being forced back to the shore by wave action and its own volition.  She thought she had discovered a baby sea turtle, or perhaps a diamondback terrapin hatchling.  A few questions cleared up the mystery.  Color?  Dark, almost black.  Long tail?  Yes, very long.  Bump along the tail?  Yes, like an ancient dinosaur.  Jagged edge along rear of carapace (top shell)?  Yep.  Does it have a yellow “button” in the middle of its tummy?  Yes.  Congratulations!  You are the proud holder of a snapping turtle hatchling.  With just a few more questions we discovered the local fresh water source from whence the hatchling probably came, either through its own design or more likely with the help of local kids.

Snapping Turtle Hatchling

You’re right.  Snapping turtles aren’t endangered and they’re not leatherbacks.  But that doesn’t diminish the joy in helping a hatchling find hospitable habitat where it might have a fighting chance of survival.  Saving one turtle … even a snapper … isn’t a bad way to close the day.

Run for Your Life

Sunday, August 24th, 2008

As tiny, defenseless, 1-inch, quarter ounce hatchlings emerge, their only hope for survival is a mad dash from exposed sandy dunes to the cover of vegetation and the nursery salt marsh.

Terrapin Hatchling Runs for Its Life